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Chapter 3

Chemical Reactions and Reaction Stoichiometry

Educators


Problem 1

The reaction between reactant A (blue spheres) and reactant $\mathrm{B}($ red spheres) is shown in the following diagram:
Based on this diagram, which equation best describes the reaction? [ Section 3.1$]$
$$
\begin{array}{l}{\text { (a) } \mathrm{A}_{2}+\mathrm{B} \longrightarrow \mathrm{A}_{2} \mathrm{B}} \\ {\text { (b) } \mathrm{A}_{2}+4 \mathrm{B} \longrightarrow 2 \mathrm{AB}_{2}} \\ {\text { (c) } 2 \mathrm{A}+\mathrm{B}_{4} \longrightarrow 2 \mathrm{AB}_{2}} \\ {\text { (d) } \mathrm{A}+\mathrm{B}_{2} \longrightarrow \mathrm{AB}_{2}}\end{array}
$$

Aadit S.
Numerade Educator

Problem 2

The following diagram shows the combination reaction between hydrogen, $\mathrm{H}_{2},$ and carbon monoxide, $\mathrm{CO},$ to produce methanol, $\mathrm{CH}_{3} \mathrm{OH}$ (white spheres are $\mathrm{H},$ black spheres are $\mathrm{C},$ red spheres are O). The correct number of CO molecules involved in this reaction is not shown. [ Section 3.1$]$
(a) Determine the number of CO molecules that should be shown in the left (reactants) box.
(b) Write a balanced chemical equation for the reaction.

Md M.
Auburn University Main Campus

Problem 3

The following diagram represents the collection of elements formed by a decomposition reaction. (a) If the blue spheres represent $N$ atoms and the red ones represent $\mathrm{O}$ atoms, what was the empirical formula of the original compound? (b) Could you draw a diagram representing the molecules of the compound that had been decomposed? Why or why not? [Section 3.2$]$

Aadit S.
Numerade Educator

Problem 4

The following diagram represents the collection of $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ molecules formed by complete combustion of a hydrocarbon. What is the empirical formula of the hydrocarbon? [Section 3.2$]$

Md M.
Auburn University Main Campus

Problem 5

Glycine, an amino acid used by organisms to make proteins, is represented by the following molecular model.
(a) Write its molecular formula.
(b) Determine its molar mass.
(c) Calculate how many moles of glycine are in a $100.0-g$ sample of glycine.
(d) Calculate the percent nitrogen by mass in glycine. [Sections 3.3 and 3.5$]$

Aadit S.
Numerade Educator

Problem 6

The following diagram represents a high-temperature reaction between $\mathrm{CH}_{4}$ and $\mathrm{H}_{2} \mathrm{O}$ . Based on this reaction, find how many moles of each product can be obtained starting with 4.0 $\mathrm{mol} \mathrm{CH}_{4} .[$ Section 3.6$]$

Md M.
Auburn University Main Campus

Problem 7

Nitrogen $\left(\mathrm{N}_{2}\right)$ and hydrogen $\left(\mathrm{H}_{2}\right)$ react to form ammonia $\left(\mathrm{NH}_{3}\right) .$ Consider the mixture of $\mathrm{N}_{2}$ and $\mathrm{H}_{2}$ shown in the accompanying diagram. The blue spheres represent $\mathrm{N},$ and the white ones represent H. (a) Write the balanced chemical equation for the reaction. (b) What is the limiting reactant? (c) How many molecules of ammonia can be made, assuming the reaction goes to completion, based on the diagram? (d) Are any reactant molecules left over, based on the diagram? If so, how many of which type are left over? [ Section 3.7]

Aadit S.
Numerade Educator

Problem 8

Nitrogen monoxide and oxygen react to form nitrogen dioxide. Consider the mixture of NO and O $_{2}$ shown in the accompanying diagram. The blue spheres represent $\mathrm{N},$ and the red ones represent $\mathrm{O}$ . (a) How many molecules of $\mathrm{NO}_{2}$ can be formed, assuming the reaction goes to completion? (b) What is the limiting reactant? (c) If the actual yield of the reaction was 75$\%$ instead of 100$\%$ , how many molecules of each kind would be present after the reaction was over?

Md M.
Auburn University Main Campus

Problem 9

Write "true" or "false" for each statement. (a) We balance chemical equations as we do because energy must be conserved. (b) If the reaction 2 $\mathrm{O}_{3}(g) \rightarrow 3 \mathrm{O}_{2}(g)$ goes to completion and all $\mathrm{O}_{3}$ is converted to $\mathrm{O}_{2},$ then the mass of $\mathrm{O}_{3}$ at the beginning of the reaction must be the same as the mass of $\mathrm{O}_{2}$ at the end of the reaction. (c) You can balance the "water-splitting" reaction $\mathrm{H}_{2} \mathrm{O}(I) \rightarrow \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g)$ by writing it this way: $\mathrm{H}_{2} \mathrm{O}_{2}(l) \rightarrow \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g)$

Aadit S.
Numerade Educator

Problem 10

A key step in balancing chemical equations is correctly identifying the formulas of the reactants and products. For example, consider the reaction between calcium oxide, CaO(s), and $\mathrm{H}_{2} \mathrm{O}(l)$ to form aqueous calcium hydroxide. (a) Write a balanced chemical equation for this combination reaction, having correctly identified the product as $\mathrm{Ca}(\mathrm{OH})_{2}(a q)$ . (b) Is it possible to balance the equation if you incorrectly identify the product as $\mathrm{CaOH}(a q),$ and if so, what is the equation?

Md M.
Auburn University Main Campus

Problem 11

Balance the following equations:
$$
\begin{array}{l}{\text { (a) } \mathrm{CO}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)} \\ {\text { (b) } \mathrm{N}_{2} \mathrm{O}_{5}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{HNO}_{3}(a q)} \\ {\text { (c) } \mathrm{CH}_{4}(g)+\mathrm{Cl}_{2}(g) \longrightarrow \mathrm{CCl}_{4}(l)+\mathrm{HCl}(g)} \\ {\text { (d) } \mathrm{Zn}(\mathrm{OH})_{2}(s)+\mathrm{HNO}_{3}(a q) \longrightarrow \mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)}\end{array}
$$

Aadit S.
Numerade Educator

Problem 12

Balance the following equations:
$$
\begin{array}{l}{\text { (a) } \mathrm{Li}(s)+\mathrm{N}_{2}(g) \longrightarrow \mathrm{Li}_{3} \mathrm{N}(s)} \\ {\text { (b) } \mathrm{TiCl}_{4}(l)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{TiO}_{2}(s)+\mathrm{HCl}(a q)} \\ {\text { (c) } \mathrm{NH}_{4} \mathrm{NO}_{3}(s) \longrightarrow \mathrm{N}_{2}(g)+\mathrm{O}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)} \\ {\text { (d) } \mathrm{AlCl}_{3}(s)+\mathrm{Ca}_{3} \mathrm{N}_{2}(s) \longrightarrow \mathrm{AlN}(s)+\mathrm{CaCl}_{2}(s)}\end{array}
$$

Md M.
Auburn University Main Campus

Problem 13

Balance the following equations:
$$
\begin{array}{l}{\text { (a) } \mathrm{Al}_{4} \mathrm{C}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{Al}(\mathrm{OH})_{3}(s)+\mathrm{CH}_{4}(g)} \\ {\text { (b) } \mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}(l)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)} \\ {\text { (c) } \mathrm{Fe}(\mathrm{OH})_{3}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)} \\ {\text { (d) } \mathrm{Mg}_{3} \mathrm{N}_{2}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \mathrm{MgSO}_{4}(a q)+\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4}(a q)}\end{array}
$$

Aadit S.
Numerade Educator

Problem 14

Balance the following equations:
$$
\begin{array}{l}{\text { (a) } \mathrm{Ca}_{3} \mathrm{P}_{2}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{Ca}(\mathrm{OH})_{2}(a q)+\mathrm{PH}_{3}(g)} \\ {\text { (b) } \mathrm{Al}(\mathrm{OH})_{3}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)} \\ {\text { (c) } \mathrm{AgNO}_{3}(a q)+\mathrm{Na}_{2} \mathrm{CO}_{3}(a q) \longrightarrow \mathrm{Ag}_{2} \mathrm{CO}_{3}(s)+\mathrm{NaNO}_{3}(a q)} \\ {\text { (d) } \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NH}_{2}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)+\mathrm{N}_{2}(g)}\end{array}
$$

Md M.
Auburn University Main Campus

Problem 15

Write balanced chemical equations corresponding to each of the following descriptions: (a) Solid calcium carbide, $\mathrm{CaC}_{2}$ , reacts with water to form an aqueous solution of calcium hydroxide and acetylene gas, $\mathrm{C}_{2} \mathrm{H}_{2}$ . (b) When solid potassium chlorate is heated, it decomposes to form solid potassium chloride and oxygen gas. (c) Solid zinc metal reacts with sulfuric acid to form hydrogen gas and an aqueous solution of zinc sulfate. (d) When liquid phosphorus trichloride is added to water, it reacts to form aqueous phosphorous acid, $\mathrm{H}_{3} \mathrm{PO}_{3}(a q)$, and aqueous hydrochloric acid. (e) When hydrogen sulfide gas is passed over solid hot iron(III) hydroxide, the resulting reaction produces solid iron(II) sulfide and gaseous water.

Aadit S.
Numerade Educator

Problem 16

Write balanced chemical equations to correspond to each of the following descriptions: (a) When sulfur trioxide gas reacts with water, a solution of sulfuric acid forms. (b) Boron sulfide, $B_{2} S_{3}(s),$ reacts violently with water to form dissolved boric acid, $H_{3} B O_{3},$ and hydrogen sulfide gas. (c) Phosphine, PH $_{3}(g),$ combusts in oxygen gas to form water vapor and solid tetraphosphorus decaoxide. (d) When solid mercury(II) nitrate is heated, it decomposes to form solid mercury(II) oxide, gaseous nitrogen dioxide, and oxygen.(e) Copper metal reacts with hot concentrated sulfuric acid solution to form aqueous copper(II) sulfate, sulfur dioxide gas, and water.

Md M.
Auburn University Main Campus

Problem 17

(a) When the metallic element sodium combines with the nonmetallic element bromine, $\mathrm{Br}_{2}(l),$ what is the chemical formula of the product? (b) Is the product a solid, liquid, or gas at room temperature? (c) In the balanced chemical equation for this reaction, what is the coefficient in front of the product if the coefficient in front of $\mathrm{Br}_{2}(l)$ is 1$?$

Aadit S.
Numerade Educator

Problem 18

(a) When a compound containing $\mathrm{C}, \mathrm{H},$ and $\mathrm{O}$ is completely combusted in air, what reactant besides the hydrocarbon is involved in the reaction? (b) What products form in this reaction? (c) What is the sum of the coefficients in the balanced chemical equation for the combustion of one mole of acetone, $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}(l),$ in air?

Md M.
Auburn University Main Campus

Problem 19

Write a balanced chemical equation for the reaction that occurs when (a) $\mathrm{Mg}(s)$ reacts with $\mathrm{Cl}_{2}(g) ;$ (b) barium carbonate decomposes into barium oxide and carbon dioxide gas when heated; (c) the hydrocarbon styrene, $\mathrm{C}_{8} \mathrm{H}_{8}(l),$ is combusted in air; (d) dimethylether, $\mathrm{CH}_{3} \mathrm{OCH}_{3}(g),$ is combusted in air.

Aadit S.
Numerade Educator

Problem 20

Write a balanced chemical equation for the reaction that occurs when (a) titanium metal reacts with $\mathrm{O}_{2}(g) ;(\mathbf{b})$ silver(I)oxide decomposes into silver metal and oxygen gas when heated; (c) propanol, $\mathrm{C}_{3} \mathrm{H}_{7} \mathrm{OH}(l)$ burns in air; (d) methyl tert-butyl ether, $\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}(l),$ burns in air.

Md M.
Auburn University Main Campus

Problem 21

Balance the following equations and indicate whether they are combination, decomposition, or combustion reactions:
$$
\begin{array}{l}{\text { (a) } \mathrm{C}_{3} \mathrm{H}_{6}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)} \\ {\text { (b) } \mathrm{NH}_{4} \mathrm{NO}_{3}(s) \longrightarrow \mathrm{N}_{2} \mathrm{O}(g)+\mathrm{H}_{2} \mathrm{O}(g)} \\ {\text { (c) } \mathrm{C}_{5} \mathrm{H}_{6} \mathrm{O}(l)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)} \\ {\text { (d) } \mathrm{N}_{2}(g)+\mathrm{H}_{2}(g) \longrightarrow \mathrm{NH}_{3}(g)} \\ {\text { (e) } \mathrm{K}_{2} \mathrm{O}(s)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{KOH}(a q)}\end{array}
$$

Aadit S.
Numerade Educator

Problem 22

Balance the following equations and indicate whether they are combination, decomposition, or combustion reactions:
$$
\begin{array}{l}{\text { (a) } \mathrm{PbCO}_{3}(s) \longrightarrow \mathrm{PbO}(s)+\mathrm{CO}_{2}(g)} \\ {\text { (b) } \mathrm{C}_{2} \mathrm{H}_{4}(g)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)} \\ {\text { (c) } \mathrm{Mg}(s)+\mathrm{N}_{2}(g) \longrightarrow \mathrm{Mg}_{3} \mathrm{N}_{2}(s)} \\ {\text { (d) } \mathrm{C}_{7} \mathrm{H}_{8} \mathrm{O}_{2}(l)+\mathrm{O}_{2}(g) \longrightarrow \mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)} \\ \text { (e) } \mathrm{Al}(s)+\mathrm{Cl}_{2}(g) \longrightarrow \mathrm{AlCl}_{3}(s) \end{array}
$$

Md M.
Auburn University Main Campus

Problem 23

Determine the formula weights of each of the following compounds: (a) nitric acid, HNO $_{3} ;$ (b) $\mathrm{KMnO}_{4} ;$ (c) $\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}$ (d) quartz, SiO $_{2} ;$ (e) gallium sulfide, (f) chromium(III) sulfate, (g) phosphorus trichloride.

Aadit S.
Numerade Educator

Problem 24

Determine the formula weights of each of the following compounds: (a) nittrous oxide, $\mathrm{N}_{2} \mathrm{O}$ , known as laughing gas and used as an anesthetic in dentistry; (b) benzoic acid; $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOH}$ a substance used as a food preservative; $(c) \mathrm{Mg}(\mathrm{OH})_{2},$ the active ingredient in milk of magnesia; (d) urea, $\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO},$ a compound used as a nitrogen fertilizer; (e) isopentyl acetate, $\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{C}_{5} \mathrm{H}_{11},$ responsible for the odor of bananas.

Md M.
Auburn University Main Campus

Problem 25

Calculate the percentage by mass of oxygen in the following compounds: (a) morphine, $\mathrm{C}_{17} \mathrm{H}_{19} \mathrm{NO}_{3} ;$ (b) codeine, $\mathrm{C}_{18} \mathrm{H}_{21} \mathrm{NO}_{3}$ (c) cocaine, $\mathrm{C}_{17} \mathrm{H}_{21} \mathrm{NO}_{4} ;(\mathbf{d})$ tetracycline, $\mathrm{C}_{22} \mathrm{H}_{24} \mathrm{N}_{2} \mathrm{O}_{8} ;(\mathbf{e})$ digi$\mathrm{toxin}, \mathrm{C}_{41} \mathrm{H}_{64} \mathrm{O}_{13} ;(\mathrm{f})$ vancomycin, $\mathrm{C}_{66} \mathrm{H}_{75} \mathrm{Cl}_{2} \mathrm{N}_{9} \mathrm{O}_{24}$.

Aadit S.
Numerade Educator

Problem 26

Calculate the percentage by mass of the indicated element in the following compounds: $(\mathbf{a})$ carbon in acetylene, $\mathrm{C}_{2} \mathrm{H}_{2}, \mathrm{a}$ gas used in welding; $(\mathbf{b} )$ hydrogen in ascorbic acid, $\mathrm{HC}_{6} \mathrm{H}_{7} \mathrm{O}_{6}$ also known as vitamin $\mathrm{C} ;(\mathbf{c})$ hydrogen in ammonium sulfate, $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4},$ a substance used as a nitrogen fertilizer; $(\mathbf{d})$ platinum in $\mathrm{PtCl}_{2}\left(\mathrm{NH}_{3}\right)_{2},$ a chemotherapy agent called cisplatin; $(\mathbf{e})$ oxygen in the female sex hormone estradiol, $\mathrm{C}_{18} \mathrm{H}_{24} \mathrm{O}_{2} ;(\mathbf{f})$ carbon in capsaicin, $\mathrm{C}_{18} \mathrm{H}_{27} \mathrm{NO}_{3},$ the compound that gives the hot taste to chili peppers.

Md M.
Auburn University Main Campus

Problem 27

Based on the following structural formulas, calculate the percentage of carbon by mass present in each compound:

Aadit S.
Numerade Educator

Problem 28

Calculate the percentage of carbon by mass in each of the compounds represented by the following models:

Md M.
Auburn University Main Campus

Problem 29

(a) Write "true" or "false" for each statement. (a) A mole of horses contain a mole of horse legs. (b) A mole of water has a mass of 18.0 $\mathrm{g} .$ (c) The mass of 1 molecule of water is 18.0 $\mathrm{g}$ (d) A mole of NaCl (s) contains 2 moles of ions.

Aadit S.
Numerade Educator

Problem 30

(a) What is the mass, in grams, of one mole of $^{12} \mathrm{C} ?$ (b) How many carbon atoms are present in one mole of $^{12} \mathrm{C} ?$

Md M.
Auburn University Main Campus

Problem 31

Without doing any detailed calculations (but using a periodic table to give atomic weights), rank the following samples in order of increasing numbers of atoms: 0.50 mol $\mathrm{H}_{2} \mathrm{O}, 23 \mathrm{g} \mathrm{Na}, 6.0 \times 10^{23} \mathrm{N}_{2}$ molecules.

Aadit S.
Numerade Educator

Problem 32

Without doing any detailed calculations (but using a periodic table to give atomic weights, rank the following samples in order of increasing numbers of atoms: 42 gof NaHCO $_{3}, 1.5 \mathrm{mol} \mathrm{CO}_{2}, 6.0 \times 10^{24} \mathrm{Ne}$ atoms.

Md M.
Auburn University Main Campus

Problem 33

What is the mass, in kilograms, of an Avogadro's number of people, if the average mass of a person is 160 $\mathrm{lb}$ ? How does this compare with the mass of Earth, $5.98 \times 10^{24} \mathrm{kg}$ ?

Aadit S.
Numerade Educator

Problem 34

If Avogadro's number of pennies is divided equally among the 321 million men, women, and children in the United States, how many dollars would each receive? How does this compare with the gross domestic product (GDP) of the United States, which was $\$ 17.419$ trillion in 2015$?$ (The GDP is the total market value of the nation's goods and services.)

Md M.
Auburn University Main Campus

Problem 35

Calculate the following quantities:
$$
\begin{array}{l}{\text { (a) mass, in grams, of } 0.105 \text { mol sucrose }\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right)} \\ {\text { (b) moles of } \mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2} \text { in } 143.50 \mathrm{g} \text { of this substance }} \\ {\text { (c) number of molecules in } 1.0 \times 10^{-6} \mathrm{mol} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}} \\ \text { (d) number of }
\mathrm{N} \text { atoms in } 0.410 \mathrm{mol} \mathrm{NH}_{3}\end{array}
$$

Aadit S.
Numerade Educator

Problem 36

Calculate the following quantities:
$$
\begin{array}{l}{\text { (a) mass, in grams, of } 1.50 \times 10^{-2} \text { mol CdS }} \\ {\text { (b) number of moles of } \mathrm{NH}_{4} \mathrm{Cl} \text { in } 86.6 \mathrm{g} \text { of this substance }} \\ {\text { (c) number of molecules in } 8.447 \times 10^{-2} \mathrm{mol} \mathrm{C}_{6} \mathrm{H}_{6}} \\ {\text { (d) number of } \mathrm{O} \text { atoms in } 6.25 \times 10^{-3} \mathrm{mol} \mathrm{Al}\left(\mathrm{NO}_{3}\right)_{3}}\end{array}
$$

Md M.
Auburn University Main Campus

Problem 37

(a) What is the mass, in grams, of $2.50 \times 10^{-3}$ mol of ammonium phosphate?
(b) How many moles of chloride ions are in 0.2550 g of aluminum chloride?
(c) What is the mass, in grams, of $7.70 \times 10^{20}$ molecules of caffeine, $\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{4} \mathrm{O}_{2} ?$
(d) What is the molar mass of cholesterol if 0.00105 $\mathrm{mol}$ has a mass of 0.406 $\mathrm{g}$ ?

Aadit S.
Numerade Educator

Problem 38

(a) What is the mass, in grams, of 1.223 mol of iron( III) sulfate?
(b) How many moles of ammonium ions are in 6.955 g of ammonium carbonate?
(c) What is the mass, in grams, of $1.50 \times 10^{21}$ molecules of aspirin, $\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4} ?$
(d) What is the molar mass of diazepam (Valium') if 0.05570 mol has a mass of 15.86 $\mathrm{g} ?$

Md M.
Auburn University Main Campus

Problem 39

The molecular formula of allicin, the compound responsible for the characteristic smell of garlic, is $\mathrm{C}_{6} \mathrm{H}_{10} \mathrm{OS}_{2}$ . (a) What is the molar mass of allicin? (b) How many moles of allicin are present in 5.00 $\mathrm{mg}$ of this substance? (c) How many molecules of allicin are in 5.00 $\mathrm{mg}$ of this substance? (d) How many S atoms are present in 5.00 $\mathrm{mg}$ of allicin?

Aadit S.
Numerade Educator

Problem 40

The molecular formula of aspartame, the artificial sweetener marketed as NutraSweet, is $\mathrm{C}_{14} \mathrm{H}_{18} \mathrm{N}_{2} \mathrm{O}_{5}$ . (a) What is the molar mass of aspartame? (b) How many moles of aspartame are present in 1.00 $\mathrm{mg}$ of aspartame? (c) How many molecules of aspartame are present in 1.00 $\mathrm{mg}$ of aspartame? (d) How many hydrogen atoms are present in 1.00 $\mathrm{mg}$ of aspartame?

Md M.
Auburn University Main Campus

Problem 41

A sample of glucose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6},$ contains $1.250 \times 10^{21}$ carbon atoms. (a) How many atoms of hydrogen does it contain? (b) How many molecules of glucose does it contain? (c) How many moles of glucose does it contain? (d) What is the mass of this sample in grams?

Aadit S.
Numerade Educator

Problem 42

A sample of the male sex hormone testosterone, $\mathrm{C}_{19} \mathrm{H}_{28} \mathrm{O}_{2}$ , contains $3.88 \times 10^{21}$ hydrogen atoms. (a) How many atoms of carbon does it contain? (b) How many molecules of testosterone does it contain? (c) How many moles of testosterone does it contain? (d) What is the mass of this sample in grams?

Md M.
Auburn University Main Campus

Problem 43

The allowable concentration level of vinyl chloride, $\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{Cl}$ , in the atmosphere in a chemical plant is $2.0 \times 10^{-6} \mathrm{g} / \mathrm{L}$ . How many moles of vinyl chloride in each liter does this represent? How many molecules per liter?

Aadit S.
Numerade Educator

Problem 44

At least 25$\mu \mathrm{g}$ of tetrahydrocannabinol $(\mathrm{THC}),$ the active ingredient in marijuana, is required to produce intoxication. The molecular formula of THC is $\mathrm{C}_{21} \mathrm{H}_{30} \mathrm{O}_{2} .$ How many moles of THC does this 25$\mu \mathrm{g}$ represent? How many molecules?

Md M.
Auburn University Main Campus

Problem 45

Give the empirical formula of each of the following compounds if a sample contains (a) 0.0130 mol $\mathrm{C}, 0.0390 \mathrm{mol}$ $\mathrm{H},$ and $0.0065 \mathrm{mol} \mathrm{O} ;$ (b) $11.66 \mathrm{g}$ iron and 5.01 $\mathrm{g}$ oxygen; (c) $40.0 \% \mathrm{C}, 6.7 \% \mathrm{H},$ and 53.3$\%$ o by mass.

Aadit S.
Numerade Educator

Problem 46

Determine the empirical formula of each of the following compounds if a sample contains $(\mathbf{a})0.104 \mathrm{mol} \mathrm{K}, 0.052 \mathrm{mol}$ $\mathrm{C},$ and $0.156 \mathrm{mol} \mathrm{O} ;(\mathbf{b}) 5.28 \mathrm{g} \mathrm{Sn}$ and $3.37 \mathrm{g} \mathrm{F} ;(\mathbf{c}) 87.5 \% \mathrm{N}$ and 12.5$\% \mathrm{H}$ by mass.

Md M.
Auburn University Main Campus

Problem 47

Determine the empirical formulas of the compounds with the following compositions by mass:
$$
\begin{array}{l}{\text { (a) } 10.4 \% \mathrm{C}, 27.8 \% \mathrm{S}, \text { and } 61.7 \% \mathrm{Cl}} \\ {\text { (b) } 21.7 \% \mathrm{C}, 9.6 \% \mathrm{O}, \text { and } 68.7 \% \mathrm{F}} \\ {\text { (c) } 32.79 \% \mathrm{Na}, 13.02 \% \mathrm{Al}, \text { and the remainder } \mathrm{F}}\end{array}
$$

Aadit S.
Numerade Educator

Problem 48

Determine the empirical formulas of the compounds with the following compositions by mass:
$$
\begin{array}{l}{\text { (a) } 55.3 \% \mathrm{K}, 14.6 \% \mathrm{P}, \text { and } 30.1 \% \mathrm{O}} \\ {\text { (b) } 24.5 \% \mathrm{Na}, 14.9 \% \mathrm{Si}, \text { and } 60.6 \% \mathrm{F}} \\ {\text { (c) } 62.1 \% \mathrm{C}, 5.21 \% \mathrm{H}, 12.1 \% \mathrm{N}, \text { and the remainder O }}\end{array}
$$

Md M.
Auburn University Main Campus

Problem 49

A compound whose empirical formula is $X F_{3}$ consists of 65$\%$ F by mass. What is the atomic mass of $X ?$

Aadit S.
Numerade Educator

Problem 50

The compound $\mathrm{XCl}_{4}$ contains 75.0$\% \mathrm{Cl}$ by mass. What is the element $\mathrm{X}$ ?

Md M.
Auburn University Main Campus

Problem 51

What is the molecular formula of each of the following compounds?
$$
\begin{array}{l}{\text { (a) empirical formula } \mathrm{CH}_{2}, \text { molar mass }=84.0 \mathrm{g} / \mathrm{mol}} \\ {\text { (b) empirical formula } \mathrm{NH}_{2} \mathrm{Cl} \text { , molar mass }=51.5 \mathrm{g} / \mathrm{mol}}\end{array}
$$

Aadit S.
Numerade Educator

Problem 52

What is the molecular formula of each of the following compounds?
$$
\begin{array}{l}{\text { (a) empirical formula } \mathrm{HCO}_{2} \text { , molar mass }=90.0 \mathrm{g} / \mathrm{mol}} \\ {\text { (b) empirical formula } \mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}, \text { molar mass }=88.0 \mathrm{g} / \mathrm{mol}}\end{array}
$$

Md M.
Auburn University Main Campus

Problem 53

Determine the empirical and molecular formulas of each of the following substances:
(a) Styrene, a compound used to make Styrofoam' cups and insulation, contains 92.3$\% \mathrm{C}$ and 7.7$\% \mathrm{H}$ by mass and has a molar mass of 104 $\mathrm{g} / \mathrm{mol} .$
(b) Caffeine, a stimulant found in coffee, contains 49.5$\% \mathrm{C}$ , $5.15 \% \mathrm{H}, 28.9 \% \mathrm{N},$ and 16.5$\% \mathrm{O}$ by mass and has a molar mass of 195 $\mathrm{g} / \mathrm{mol} .$
(c) Monosodium glutamate (MSG), a flavor enhancer in certain foods, contains $35.51 \% \mathrm{C}, 4.77 \% \mathrm{H}, 37.85 \% \mathrm{O}$ , $8.29 \% \mathrm{N},$ and 13.60$\% \mathrm{Na}$ , and has a molar mass of 169 $\mathrm{g} / \mathrm{mol} .$

Aadit S.
Numerade Educator

Problem 54

Determine the empirical and molecular formulas of each of the following substances:
(a) Ibuprofen, a headache remedy, contains 75.69$\% \mathrm{C}$ , $8.80 \% \mathrm{H},$ and 15.51$\% \mathrm{O}$ by mass and has a molar mass of 206 $\mathrm{g} / \mathrm{mol} .$
(b) Cadaverine, a foul-smelling substance produced by the action of bacteria on meat, contains 58.55$\% \mathrm{C}$ , $13.81 \% \mathrm{H},$ and 27.40$\% \mathrm{N}$ by mass; its molar mass is 102.2 $\mathrm{g} / \mathrm{mol}$
(c) Epinephrine (adrenaline), a hormone secreted into the bloodstream in times of danger or stress, contains 59.0$\%$ C, $7.1 \% \mathrm{H}, 26.2 \% \mathrm{O},$ and 7.7$\% \mathrm{N}$ by mass; its molar mass is about 180 amu.

Md M.
Auburn University Main Campus

Problem 55

(a) Combustion analysis of toluene, a common organic solvent, gives 5.86 $\mathrm{mg}$ of $\mathrm{CO}_{2}$ and 1.37 $\mathrm{mg}$ of $\mathrm{H}_{2} \mathrm{O}$ . If the compound contains only carbon and hydrogen, what is its empirical formula? (b) Menthol, the substance can smell in mentholated cough drops, is composed of $\mathrm{C}, \mathrm{H},$ and $\mathrm{O} . \mathrm{A}$ 0.1005 -gsample of mentholis combusted, producing 0.2829 $\mathrm{g}$ of $\mathrm{CO}_{2}$ and 0.1159 $\mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O} .$ What is the empirical formula for menthol? If menthol has a molar mass of 156 $\mathrm{g} / \mathrm{mol}$ what is its molecular formula?

Aadit S.
Numerade Educator

Problem 56

(a) The characteristic odor of pineapple is due to ethyl butyrate, a compound containing carbon, hydrogen, and oxygen. Combustion of 2.78 mg of ethyl butyrate produces 6.32 $\mathrm{mg}$ of $\mathrm{CO}_{2}$ and 2.58 $\mathrm{mg}$ of $\mathrm{H}_{2} \mathrm{O} .$ What is the empirical formula of the compound? (b) Nicotine, a component of tobacco, is composed of $C, H,$ and $N .$ A 5.250 -mg sample of nicotine was combusted, producing 14.242 $\mathrm{mg}$ of $\mathrm{CO}_{2}$ and 4.083 $\mathrm{mg}$ of $\mathrm{H}_{2} \mathrm{O} .$ What is the empirical formula for nicotine? If nicotine has a molar mass of $160 \pm 5 \mathrm{g} / \mathrm{mol},$ what is its molecular formula?

Md M.
Auburn University Main Campus

Problem 57

Valproic acid, used to treat seizures and bipolar disorder, is composed of $\mathrm{C}, \mathrm{H},$ and $\mathrm{O} . \mathrm{A}$ . $165-\mathrm{g}$ sample is combusted to produce 0.166 $\mathrm{g}$ of water and 0.403 $\mathrm{g}$ of carbon dioxide. What is the empirical formula for valproic acid? If the molar mass is $144 \mathrm{g} / \mathrm{mol},$ what is the molecular formula?

Aadit S.
Numerade Educator

Problem 58

Propenoic acid, $\mathrm{C}_{3} \mathrm{H}_{4} \mathrm{O}_{2},$ is a reactive organic liquid that is used in the manufacturing of plastics, coatings, and adhesives. An unlabeled container is thought to contain this liquid. A 0.275 -g sample of the liquid is combusted to produce 0.102 gof water and 0.374 g carbon dioxide. Is the unknown liquid propenoic acid? Support your reasoning with calculations.

Md M.
Auburn University Main Campus

Problem 59

Washing soda, a compound used to prepare hard water for washing laundry, is a hydrate, which means that a certain number of water molecules are included in the solid structure. Its formula can be written as $\mathrm{Na}_{2} \mathrm{CO}_{3} \cdot x \mathrm{H}_{2} \mathrm{O},$ where $x$ is the number of moles of $\mathrm{H}_{2} \mathrm{O}$ per mole of $\mathrm{Na}_{2} \mathrm{CO}_{3} .$ When a 2.558 -g sample of washing soda is heated at $125^{\circ} \mathrm{C}$ , all the water of hydration is lost, leaving 0.948 $\mathrm{g}$ of $\mathrm{Na}_{2} \mathrm{CO}_{3} .$ What is the value of $x ?$

Aadit S.
Numerade Educator

Problem 60

Epsom salts, a strong laxative used in veterinary medicine, is a hydrate, which means that a certain number of water molecules are included in the solid structure. The formula for Epsom salts can be written as $\mathrm{MgSO}_{4} \cdot x \mathrm{H}_{2} \mathrm{O},$ where $x$ indicates the number of moles of $\mathrm{H}_{2} \mathrm{O}$ per mole of $\mathrm{MgSO}_{4}$ When 5.061 $\mathrm{g}$ of this hydrate is heated to $250^{\circ} \mathrm{C},$ all the water of hydration is lost, leaving 2.472 g of MgSO $_{4} .$ What is the value of $x ?$

Md M.
Auburn University Main Campus

Problem 61

Hydrofluoric acid, HF(aq), cannot be stored in glass bottles because compounds called silicates in the glass are attacked by the HF(aq). Sodium silicate (Na $_{2} \mathrm{SiO}_{3} ),$ for example, reacts as follows:
$$
\mathrm{Na}_{2} \mathrm{SiO}_{3}(s)+8 \mathrm{HF}(a q) \longrightarrow \mathrm{H}_{2} \mathrm{SiF}_{6}(a q)+2 \operatorname{NaF}(a q)+3 \mathrm{H}_{2} \mathrm{O}(l)
$$
(a) How many moles of HF are needed to react with 0.300 mol of $\mathrm{Na}_{2} \mathrm{SiO}_{3} ?$
(b) How many grams of NaF form when 0.500 mol of HF reacts with excess $\mathrm{Na}_{2} \mathrm{SiO}_{3} ?$
(c) How many grams of $\mathrm{Na}_{2} \mathrm{SiO}_{3}$ can react with 0.800 g of HF?

Aadit S.
Numerade Educator

Problem 62

The reaction between potassium superoxide, $\mathrm{KO}_{2},$ and $\mathrm{CO}_{2}$
$$
4 \mathrm{KO}_{2}+2 \mathrm{CO}_{2} \longrightarrow 2 \mathrm{K}_{2} \mathrm{CO}_{3}+3 \mathrm{O}_{2}
$$
is used as a source of $\mathrm{O}_{2}$ and absorber of $\mathrm{CO}_{2}$ in self-contained breathing equipment used by rescue workers.
(a) How many moles of $\mathrm{O}_{2}$ are produced when 0.400 $\mathrm{mol}$ of $\mathrm{KO}_{2}$ reacts in this fashion?
(b) How many grams of $\mathrm{KO}_{2}$ are needed to form 7.50 $\mathrm{g}$ of $\mathrm{O}_{2} ?$
(c) How many grams of $\mathrm{CO}_{2}$ are used when 7.50 $\mathrm{g}$ of $\mathrm{O}_{2}$ are produced?

Md M.
Auburn University Main Campus

Problem 63

Several brands of antacids use Al(OH) $_{3}$ to react with stomach acid, which contains primarily HCl:
$$
\mathrm{Al}(\mathrm{OH})_{3}(s)+\mathrm{HCl}(a q) \longrightarrow \mathrm{AlCl}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)
$$
(a) Balance this equation.
(b) Calculate the number of grams of HCl that can react with 0.500 g of $\mathrm{Al (\mathrm{OH})_{3}$ .
(c) Calculate the number of grams of $\mathrm{AlCl}_{3}$ and the number of grams of $\mathrm{H}_{2} \mathrm{O}$ formed when 0.500 $\mathrm{g}$ of $\mathrm{Al} (\mathrm{OH})_{3}$ reacts.
(d) Show that your calculations in parts (b) and (c) are consistent with the law of conservation of mass.

Aadit S.
Numerade Educator

Problem 64

An iron ore sample contains $\mathrm{Fe}_{2} \mathrm{O}_{3}$ together with other substances. Reaction of the ore with CO produces iron metal:
$$
\mathrm{Fe}_{2} \mathrm{O}_{3}(s)+\mathrm{CO}(g) \longrightarrow \mathrm{Fe}(s)+\mathrm{CO}_{2}(g)
$$
(a) Balance this equation.
(b) Calculate the number of grams of CO that can react with 0.350 $\mathrm{kg}$ of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ .
(c) Calculate the number of grams of Fe and the number of grams of $\mathrm{CO}_{2}$ formed when 0.350 $\mathrm{kg}$ of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ reacts.
(d) Show that your calculations in parts (b) and (c) are consistent with the law of conservation of mass.

Md M.
Auburn University Main Campus

Problem 65

Aluminum sulfide reacts with water to form aluminum hydroxide and hydrogen sulfide. (a) Write the balanced chemical equation for this reaction. (b) How many grams of aluminum hydroxide are obtained from 14.2 $\mathrm{g}$ of aluminum sulfide?

Aadit S.
Numerade Educator

Problem 66

Calcium hydride reacts with water to form calcium hydroxide and hydrogen gas. (a) Write a balanced chemical equation for the reaction. (b) How many grams of calcium hydride are needed to form 4.500 g of hydrogen?

Md M.
Auburn University Main Campus

Problem 67

Automotive air bags inflate when sodium azide, $\mathrm{NaN}_{3}$ , rapidly decomposes to its component elements:
$$
2 \mathrm{NaN}_{3}(s) \longrightarrow 2 \mathrm{Na}(s)+3 \mathrm{N}_{2}(g)
$$
(a) How many moles of $\mathrm{N}_{2}$ are produced by the decomposition of 1.50 $\mathrm{mol}$ of $\mathrm{NaN}_{3} ?$
(b) How many grams of NaN $_{3}$ are required to form 10.0 $\mathrm{g}$ of nitrogen gas?
(c) How many grams of NaN $_{3}$ are required to produce 10.0 $\mathrm{ft}^{3}$ of nitrogen gas, about the size of an automotive air bag, if the gas has a density of 1.25 $\mathrm{g} / \mathrm{L} ?$

Aadit S.
Numerade Educator

Problem 68

The complete combustion of octane, $\mathrm{C}_{8} \mathrm{H}_{18},$ a component of gasoline, proceeds as follows:
$$
2 \mathrm{C}_{8} \mathrm{H}_{18}(I)+25 \mathrm{O}_{2}(g) \longrightarrow 16 \mathrm{CO}_{2}(g)+18 \mathrm{H}_{2} \mathrm{O}(g)
$$
(a) How many moles of $\mathrm{O}_{2}$ are needed to burn 1.50 $\mathrm{mol}$ of $\mathrm{C}_{8} \mathrm{H}_{18}$ ?
(b) How many grams of $\mathrm{O}_{2}$ are needed to burn 10.0 $\mathrm{g}$ of $\mathrm{C}_{8} \mathrm{H}_{18}$ ?
(c) Octane has a density of 0.692 $\mathrm{g} / \mathrm{mL}$ at $20^{\circ} \mathrm{C} .$ How many grams of $\mathrm{O}_{2}$ are required to burn 15.0 $\mathrm{gal}$ of $\mathrm{C}_{8} \mathrm{H}_{18}$ (the capacity of an average fuel tank)?
(d) How many grams of $\mathrm{CO}_{2}$ are produced when 15.0 gal of $\mathrm{C}_{8} \mathrm{H}_{18}$ are combusted?

Md M.
Auburn University Main Campus

Problem 69

A piece of aluminum foil 1.00 $\mathrm{cm}^{2}$ and 0.550 -mm thick is allowed to react with bromine to form aluminum bromide.
(a) How many moles of aluminum were used? (The density of aluminum is 2.699 $\mathrm{g} / \mathrm{cm}^{3} .$ ) (b) How many grams of aluminum bromide form, assuming the aluminum reacts completely?

Aadit S.
Numerade Educator

Problem 70

Detonation of nitroglycerin proceeds as follows:
$$
4 \mathrm{C}_{3} \mathrm{H}_{5} \mathrm{N}_{3} \mathrm{O}_{9}(l) \longrightarrow \\
\quad \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad12 \mathrm{CO}_{2}(g)+6 \mathrm{N}_{2}(g)+\mathrm{O}_{2}(g)+10 \mathrm{H}_{2} \mathrm{O}(g)
$$
(a) If a sample containing 2.00 $\mathrm{mL}$ of nitroglycerin (density $=$ 1.592 $\mathrm{g} / \mathrm{mL}$ ) is detonated, how many moles of gas are produced? (b) If each mole of gas occupies 55 Lunder the conditions of the explosion, how many liters of gas are produced? (c) How many grams of $\mathrm{N}_{2}$ are produced in the detonation?

Md M.
Auburn University Main Campus

Problem 71

The combustion of one mole of liquid ethanol, $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}$ , produces 1367 $\mathrm{kJ}$ of heat. Calculate how much heat is produced when 235.0 $\mathrm{g}$ of ethanol are combusted.

Aadit S.
Numerade Educator

Problem 72

The combustion of one mole of liquid octane, $\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{6} \mathrm{CH}_{3}$ produces 5470 $\mathrm{kJ}$ of heat. Calculate how much heat is produced if 1.000 gallon of octane is combusted. See Exercise 3.68 for necessary information about octane.

Md M.
Auburn University Main Campus

Problem 73

(a) Define the terms limiting reactant and excess reactant. (b) Why are the amounts of products formed in a reaction determined only by the amount of the limiting reactant? (c) Why should you base your choice of which compound is the limiting reactant on its number of initial moles, not on its initial mass in grams?

Aadit S.
Numerade Educator

Problem 74

Define the terms theoretical yield, actual yield, and percent yield. (b) Why is the actual yield in a reaction almost always less than the theoretical yield?(c) Can a reaction ever have 110$\%$ actual yield?

Md M.
Auburn University Main Campus

Problem 75

Consider the mixture of ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH},$ and $\mathrm{O}_{2}$ shown in the accompanying diagram. (a) Write a balanced equation for the combustion reaction that occurs between ethanol and oxygen. (b) Which reactant is the limiting reactant? (c) How many molecules of $\mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{O}, \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH},$ and $\mathrm{O}_{2}$ will be present if the reaction goes to completion?

Aadit S.
Numerade Educator

Problem 76

Consider the mixture of propane, $\mathrm{C}_{3} \mathrm{H}_{8},$ and $\mathrm{O}_{2}$ shown here. (a) Write a balanced equation for the combustion reaction that occurs between propane and oxygen. (b) Which reactant is the limiting reactant? (c) How many molecules of $\mathrm{CO}_{2}, \mathrm{H}_{2} \mathrm{O}, \mathrm{C}_{3} \mathrm{H}_{8}$ and $\mathrm{O}_{2}$ will be present if the reaction goes to completion?

Md M.
Auburn University Main Campus

Problem 77

Sodium hydroxide reacts with carbon dioxide as follows:
$$
2 \mathrm{NaOH}(s)+\mathrm{CO}_{2}(g) \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3}(s)+\mathrm{H}_{2} \mathrm{O}(l)
$$
Which is the limiting reactant when 1.85 mol $\mathrm{NaOH}$ and 1.00 $\mathrm{mol} \mathrm{CO}_{2}$ are allowed to react? How many moles of $\mathrm{Na}_{2} \mathrm{CO}_{3}$ can be produced? How many moles of the excess reactant remain after the completion of the reaction?

Aadit S.
Numerade Educator

Problem 78

Aluminum hydroxide reacts with sulfuric acid as follows:
$$
2 \mathrm{Al}(\mathrm{OH})_{3}(s)+3 \mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}(a q)+6 \mathrm{H}_{2} \mathrm{O}(l)
$$
Which is the limiting reactant when 0.500 mol $\mathrm{Al}(\mathrm{OH})_{3}$ and 0.500 $\mathrm{mol} \mathrm{H}_{2} \mathrm{SO}_{4}$ are allowed to react? How many moles of $\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}$ can form under these conditions? How many moles of the excess reactant remain after the completion of the reaction?

Md M.
Auburn University Main Campus

Problem 79

The fizz produced when an Alka-Seltzer tablet is dissolved in water is due to the reaction between sodium bicarbonate $\left(\mathrm{NaHCO}_{3}\right)$ and citric acid $\left(\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}\right) :$
$$
\begin{aligned} 3 \mathrm{NaHCO}_{3}(a q)+\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(a q) & \longrightarrow \\ & 3 \mathrm{CO}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{Na}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(a q) \end{aligned}
$$
In a certain experiment 1.00 g of sodium bicarbonate and 1.00 g of citric acid are allowed to react. (a) Which is the limiting reactant? (b) How many grams of carbon dioxide form? (c) How many grams of the excess reactant remain after the limiting reactant is completely consumed?

Aadit S.
Numerade Educator

Problem 80

One of the steps in the commercial process for converting ammonia to nitric acid is the conversion of $\mathrm{NH}_{3}$ to $\mathrm{NO} :$
$$
4 \mathrm{NH}_{3}(g)+5 \mathrm{O}_{2}(g) \longrightarrow 4 \mathrm{NO}(g)+6 \mathrm{H}_{2} \mathrm{O}(g)
$$
In a certain experiment, 2.00 $\mathrm{g}$ of $\mathrm{NH}_{3}$ reacts with 2.50 $\mathrm{g}$ of $\mathrm{O}_{2} .$ (a) Which is the limiting reactant? (b) How many grams of $\mathrm{NO}$ and $\mathrm{H}_{2} \mathrm{O}$ form? (c) How many grams of the excess reactant remain after the limiting reactant is completely consumed? (d) Show that your calculations in parts (b) and (c) are consistent with the law of conservation of mass.

Md M.
Auburn University Main Campus

Problem 81

Solutions of sodium carbonate and silver nitrate react to form solid silver carbonate and a solution of sodium nitrate. A solution containing 3.50 $\mathrm{g}$ of sodium carbonate is mixed with one containing 5.00 $\mathrm{g}$ of silver nitrate. How many grams of sodium carbonate, silver nitrate, silver carbonate, and sodium nitrate are present after the reaction is complete?

Aadit S.
Numerade Educator

Problem 82

Solutions of sulfuric acid and lead(II) acetate react to form solid lead(II) sulfate and a solution of acetic acid. If 5.00 g of sulfuric acid and 5.00 g of lead(II) acetate are mixed, calculate the number of grams of sulfuric acid, lead(II) acetate, lead(II) sulfate, and acetic acid present in the mixture after the reaction is complete.

Md M.
Auburn University Main Campus

Problem 83

When benzene $\left(\mathrm{C}_{6} \mathrm{H}_{6}\right)$ reacts with bromine $\left(\mathrm{Br}_{2}\right),$ bromobenzene $\left(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{Br}\right)$ is obtained:
$$
\mathrm{C}_{6} \mathrm{H}_{6}+\mathrm{Br}_{2} \longrightarrow \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{Br}+\mathrm{HBr}
$$
(a) When 30.0 g of benzene reacts with 65.0 g of bromine, what is the theoretical yield of bromobenzene? (b) If the actual yield of bromobenzene is $42.3 \mathrm{g},$ what is the percentage yield?

Aadit S.
Numerade Educator

Problem 84

When ethane $\left(\mathrm{C}_{2} \mathrm{H}_{6}\right)$ reacts with chlorine $\left(\mathrm{Cl}_{2}\right),$ the main product is $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}$ , but other products containing $\mathrm{Cl},$ such as $\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{Cl}_{2},$ are also obtained in small quantities. The formation of these other products reduces the yield of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}$ (a) Calculate the theoretical yield of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}$ when 125 $\mathrm{g}$ of $\mathrm{C}_{2} \mathrm{H}_{6}$ reacts with 255 $\mathrm{g}$ of $\mathrm{Cl}_{2},$ assuming that $\mathrm{C}_{2} \mathrm{H}_{6}$ and $\mathrm{Cl}_{2}$ react only to form $\mathrm{C}_{2} \mathrm{H}_{2} \mathrm{Cl}$ and $\mathrm{HCl} .(\mathbf{b})$ Calculate the percent yield of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}$ if the reaction produces 206 $\mathrm{g}$ of $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}$

Md M.
Auburn University Main Campus

Problem 85

Hydrogen sulfide is an impurity in natural gas that must be removed. One common removal method is called the Claus process, which relies on the reaction:
$$
8 \mathrm{H}_{2} \mathrm{S}(g)+4 \mathrm{O}_{2}(g) \longrightarrow \mathrm{S}_{8}(l)+8 \mathrm{H}_{2} \mathrm{O}(g)
$$
Under optimal conditions the Claus process gives 98$\%$ yield of $S_{8}$ from $\mathrm{H}_{2}$ . If you started with 30.0 g of $\mathrm{H}_{2} \mathrm{S}$ and 50.0 $\mathrm{g}$ of $\mathrm{O}_{2},$ how many grams of $\mathrm{S}_{8}$ would be produced, assuming 98$\%$ yield?

Aadit S.
Numerade Educator

Problem 86

When hydrogen sulfide gas is bubbled into a solution of sodium hydroxide, the reaction forms sodium sulfide and water. How many grams of sodium sulfide are formed if 1.25 $\mathrm{g}$ of hydrogen sulfide is bubbled into a solution containing 2.00 g of sodium hydroxide, assuming that the sodium sulfide is made in 92.0$\%$ yield?

Md M.
Auburn University Main Campus

Problem 87

Write the balanced chemical equations for (a) the complete combustion of acetic acid $\left(\mathrm{CH}_{3} \mathrm{COOH}\right),$ the main ingredient in vinegar; (b) the decomposition of solid calcium hydroxide into solid calcium oxide (lime) and water vapor; (c) the combination reaction between nickel metal and chlorine gas.

Aadit S.
Numerade Educator

Problem 88

If $1.5 \mathrm{mol} \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}, 1.5 \mathrm{mol} \mathrm{C}_{3} \mathrm{H}_{8},$ and 1.5 $\mathrm{mol} \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COCH}_{3}$ are completely combusted in oxygen, which produces the largest number of moles of $\mathrm{H}_{2} \mathrm{O} ?$ Which produces the least? Explain.

Md M.
Auburn University Main Campus

Problem 89

The effectiveness of nitrogen fertilizers depends on both their ability to deliver nitrogen to plants and the amount of nitrogen they can deliver. Four common nitrogen-containing fertilizers are ammonia, ammonium nitrate, ammonium sulfate, and urea $\left[\left(\mathrm{NH}_{2}\right)_{2} \mathrm{CO}\right]$ . Rank these fertilizers in terms of the mass percentage nitrogen they contain.

Aadit S.
Numerade Educator

Problem 90

(a) The molecular formula of acetylsalicylic acid (aspirin), one of the most common pain relievers, is $\mathrm{CgH}_{8} \mathrm{O}_{4} .$ How many moles of $\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}$ are in a $0.500-\mathrm{g}$ tablet of aspirin? Assume the tablet is composed entirely of aspirin. (b) How many molecules of $\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}$ are in this tablet? (c) How many carbon atoms are in the tablet?

Md M.
Auburn University Main Campus

Problem 91

Very small semiconductor crystals, composed of approximately 1000 to $10,000$ atoms, are called quantum dots. Quantum dots made of the semiconductor Case are now being used in electronic reader and tablet displays because they emit light efficiently and in multiple colors, depending on dot size. The density of CdSe is 5.82 $\mathrm{g} / \mathrm{cm}^{3} .$
(a) What is the mass of one 2.5 -nm CdSe quantum dot?
(b) CdSe quantum dots that are 2.5 $\mathrm{nm}$ in diameter emit blue light upon stimulation. Assuming that the dot is a perfect sphere and that the empty space in the dot can be neglected, calculate how many Cd atoms are in one quantum dot of this size.
(c) What is the mass of one 6.5-nm CdSe quantum dot?
(d) CdSe quantum dots that are 6.5 $\mathrm{nm}$ in diameter emit red light upon stimulation. Assuming that the dot is a perfect sphere, calculate how many Cd atoms are in one quantum dot of this size.
(e) If you wanted to make one 6.5 -nm dot from multiple $2.5-$nm dots, how many 2.5 -nm dots would you need, and how many CdSe formula units would be left over, if any?

Aadit S.
Numerade Educator

Problem 92

(a) One molecule of the antibiotic penicillin G has a mass of $5.342 \times 10^{-21} \mathrm{g} .$ What is the molar mass of penicillin G? (b) Hemoglobin, the oxygen-carrying protein in red blood cells, has four iron atoms per molecule and contains 0.340$\%$ iron by mass. Calculate the molar mass of hemoglobin.

Md M.
Auburn University Main Campus

Problem 93

Serotonin is a compound that conducts nerve impulses in the brain. It contains $68.2 \% \mathrm{C}, 6.86 \% \mathrm{H}, 15.9 \% \mathrm{N},$ and 9.08$\% \mathrm{O}$ . Its molar mass is 176 $\mathrm{g} / \mathrm{mol} .$ Determine its molecular formula.

Aadit S.
Numerade Educator

Problem 94

The koala dines exclusively on eucalyptus leaves. Its digestive system detoxifies the eucalyptus oil, a poison to other animals. The chief constituent in eucalyptus oil is a substance called eucalyptol, which contains $77.87 \% \mathrm{C}, 11.76 \% \mathrm{H},$ and the remainder O. (a) What is the empirical formula for this substance? (b) A mass spectrum of eucalyptol shows a peak at about 154 amu. What is the molecular formula of the substance?

Md M.
Auburn University Main Campus

Problem 95

Vanillin, the dominant flavoring in vanilla, contains $\mathrm{C}, \mathrm{H}$ , and $\mathrm{O} .$ When 1.05 $\mathrm{g}$ of this substance is completely combusted, 2.43 $\mathrm{g}$ of $\mathrm{CO}_{2}$ and 0.50 $\mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O}$ are produced. What is the empirical formula of vanillin?

Aadit S.
Numerade Educator

Problem 96

An organic compound was found to contain only $\mathrm{C}, \mathrm{H},$ and Cl. When a $1.50-\mathrm{g}$ sample of the compound was completely combusted in air, 3.52 $\mathrm{g}$ of $\mathrm{CO}_{2}$ was formed. In a separate experiment, the chlorine in a $1.00-\mathrm{g}$ sample of the compound was converted to 1.27 g of AgCl. Determine the empirical formula of the compound.

Md M.
Auburn University Main Campus

Problem 97

A compound, $\mathrm{KBrO}_{x},$ where $x$ is unknown, is analyzed and found to contain 52.92$\%$ Br. What is the value of $x ?$

Aadit S.
Numerade Educator

Problem 98

An element $X$ forms an iodide $\left(\mathrm{XI}_{3}\right)$ and a chloride $\left(\mathrm{XCl}_{3}\right) .$ The iodide is quantitatively converted to the chloride when
it is heated in a stream of chlorine:
$$
2 \mathrm{XI}_{3}+3 \mathrm{Cl}_{2} \longrightarrow 2 \mathrm{XCl}_{3}+3 \mathrm{I}_{2}
$$
If 0.5000 $\mathrm{g}$ of $\mathrm{XI}_{3}$ is treated with chlorine, 0.2360 $\mathrm{g}$ of $\mathrm{XCl}_{3}$ is obtained. (a) Calculate the atomic weight of the element X. (b) Identify the element X.

Md M.
Auburn University Main Campus

Problem 99

A method used by the U.S. Environmental Protection Agency $($ EPA) for determining the concentration of ozone in airis to pass the air sample through a "bubbler" containing sodium iodide, which removes the ozone according to the following equation:
$$
\begin{array}{c}{\mathrm{O}_{3}(g)+2 \operatorname{NaI}(a q)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow} \\ \quad \quad \quad \quad \quad \quad\quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad{\mathrm{O}_{2}(g)+\mathrm{I}_{2}(s)+2 \mathrm{NaOH}(a q)}\end{array}
$$
(a) How many moles of sodium iodide are needed to remove $5.95 \times 10^{-6} \mathrm{mol}$ of $\mathrm{O}_{3} ?(\mathbf{b})$ How many grams of sodium iodide are needed to remove 1.3 $\mathrm{mg}$ of $\mathrm{O}_{3} ?$

Aadit S.
Numerade Educator

Problem 100

A chemical plant uses electrical energy to decompose aqueous solutions of NaCl to give $\mathrm{Cl}_{2}, \mathrm{H}_{2},$ and $\mathrm{NaOH} :$
$$
2 \mathrm{NaCl}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 2 \mathrm{NaOH}(a q)+\mathrm{H}_{2}(g)+\mathrm{Cl}_{2}(g)
$$
If the plant produces $1.5 \times 10^{6} \mathrm{kg}\left(1500$ metric tons) of $\mathrm{Cl}_{2}\right.$ daily, estimate the quantities of $\mathrm{H}_{2}$ and $\mathrm{NaOH}$ produced.

Md M.
Auburn University Main Campus

Problem 101

The fat stored in a camel's hump is a source of both energy and water. Calculate the mass of $\mathrm{H}_{2} \mathrm{O}$ produced by the metabolism of 1.0 $\mathrm{kg}$ of fat, assuming the fat consists entirely of tristearin $\left(\mathrm{C}_{57} \mathrm{H}_{110} \mathrm{O}_{6}\right),$ a typical animal fat, and assuming that during metabolism, tristearin reacts with $\mathrm{O}_{2}$ to form only $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ .

Aadit S.
Numerade Educator

Problem 102

When hydrocarbons are burned in a limited amount of air, both CO and $\mathrm{CO}_{2}$ form. When 0.450 g of a particular hydrocarbon was burned in air, 0.467 $\mathrm{g}$ of $\mathrm{CO}, 0.733 \mathrm{g}$ of $\mathrm{CO}_{2},$ and 0.450 $\mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O}$ were formed. (a) What is the empirical formula of the compound? (b) How many grams of O $_{2}$ were used in the reaction? (c) How many grams would have been required for complete combustion?

Md M.
Auburn University Main Campus

Problem 103

A mixture of $\mathrm{N}_{2}(g)$ and $\mathrm{H}_{2}(g)$ reacts in a closed container to form ammonia, $\mathrm{NH}_{3}(g) .$ The reaction ceases before either reactant has been totally consumed. At this stage $3.0 \mathrm{mol} \mathrm{N}_{2}, 3.0 \mathrm{mol} \mathrm{H}_{2},$ and 3.0 $\mathrm{mol} \mathrm{NH}_{3}$ are present. How many moles of $\mathrm{N}_{2}$ and $\mathrm{H}_{2}$ were present originally?

Aadit S.
Numerade Educator

Problem 104

A mixture containing $\mathrm{KClO}_{3}, \mathrm{K}_{2} \mathrm{CO}_{3}, \mathrm{KHCO}_{3},$ and $\mathrm{KCl}$ was heated, producing $\mathrm{CO}_{2}, \mathrm{O}_{2},$ and $\mathrm{H}_{2} \mathrm{O}$ gases according to the following equations:
$$
\begin{array}{l}{2 \mathrm{KClO}_{3}(s) \longrightarrow 2 \mathrm{KCl}(s)+3 \mathrm{O}_{2}(g)} \\ {2 \mathrm{KHCO}_{3}(s) \longrightarrow \mathrm{K}_{2} \mathrm{O}(s)+\mathrm{H}_{2} \mathrm{O}(g)+2 \mathrm{CO}_{2}(g)} \\ {\mathrm{K}_{2} \mathrm{CO}_{3}(s) \longrightarrow \mathrm{K}_{2} \mathrm{O}(s)+\mathrm{CO}_{2}(g)}\end{array}
$$
The KCl does not react under the conditions of the reaction. If 100.0 g of the mixture produces 1.80 $\mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O}, 13.20 \mathrm{g}$ of $\mathrm{CO}_{2}$ and 4.00 $\mathrm{g}$ of $\mathrm{O}_{2},$ what was the composition of the original mixture? (Assume complete decomposition of the mixture.)

Md M.
Auburn University Main Campus

Problem 105

When a mixture of 10.0 g of acetylene $\left(\mathrm{C}_{2} \mathrm{H}_{2}\right)$ and 10.0 $\mathrm{g}$ of oxygen $\left(\mathrm{O}_{2}\right)$ is ignited, the resulting combustion reaction produces $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ . (a) Write the balanced chemical equation for this reaction. (b) Which is the limiting reactant? (c) How many grams of $\mathrm{C}_{2} \mathrm{H}_{2}, \mathrm{O}_{2}, \mathrm{CO}_{2},$ and $\mathrm{H}_{2} \mathrm{O}$ are present after the reaction is complete?

Aadit S.
Numerade Educator

Problem 106

The semiconductor gallium arsenide, GaAs, is used in high-speed integrated circuits, light-emitting diodes, and solar cells. Its density is 5.32 $\mathrm{g} / \mathrm{m}^{3} .$ It can be made by reacting trimethylgallium, $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Ga},$ with arsine gas, $\mathrm{AsH}_{3}$ . The other product of the reaction is methane, $\mathrm{CH}_{4}$ . (a) If you reacted 450.0 g of trimethylgallium with 300.0 $\mathrm{g}$ of arsine, what mass of GaAs could you make? (b) Which reactant, if any, would be left over, and how many moles of the leftover reactant would remain? (c) One application of GaAs uses it as a thin film. If you take the mass of GaAs from part (a) and make a 40 -nm thin film from it, what area, in $\mathrm{cm}^{2},$ would it cover? Recall that $1 \mathrm{nm}=1 \times 10^{-9} \mathrm{m} .$

Md M.
Auburn University Main Campus

Problem 107

Paclitaxel, $\mathrm{C}_{47} \mathrm{H}_{51} \mathrm{NO}_{14},$ is an anticancer compound that is difficult to make in the lab. One reported synthesis requires 11 steps, and the final yield of paclitaxel is only 5$\% .$ Assuming all steps have equivalent yields, what is the average percent yield for each step in the synthesis?

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Problem 108

Consider a sample of calcium carbonate in the form of a cube measuring 2.005 in. on each edge. If the sample has a density of 2.71 $\mathrm{g} / \mathrm{cm}^{3}$ , how many oxygen atoms does it contain?

Md M.
Auburn University Main Campus

Problem 109

(a) You are given a cube of silver metal that measures 1.000 $\mathrm{cm}$ on each edge. The density of silver is 10.5 $\mathrm{g} / \mathrm{cm}^{3} .$ How many atoms are in this cube? (b) Because atoms are spherical, they cannot occupy all of the space of the cube. The volume of the solid is actually filled with the silver atoms. Calculate the volume of a single silver atom.(c) Using the volume of a silver atom and the formula for the volume of a sphere, calculate the radius in angstroms of a silver atom.

Aadit S.
Numerade Educator

Problem 110

(a) If an automobile travels 225 mi with a gas mileage of 20.5 mi/gal, how many kilograms of $\mathrm{CO}_{2}$ are produced? Assume that the gasoline is composed of octane, $\mathrm{C}_{8} \mathrm{H}_{18}(l),$ whose density is 0.692 $\mathrm{g} / \mathrm{mL}$ . (b) Repeat the calculation for a truck that has a gas mileage of 5 $\mathrm{mi} / \mathrm{gal} .$

Md M.
Auburn University Main Campus

Problem 111

Introduced the idea of structural isomerism, with 1 -propanol and 2 -propanol as examples. Determine which of these properties would distinguish these two substances: (a) boiling point, (b) combustion analysis results, (c) molecular weight, (d) density at a given temperature and pressure. You can check on the properties of these two compounds in Wolfram Alpha (http://www. wolframalpha.com/) or the CRC Handbook of Chemistry and Physics.

Aadit S.
Numerade Educator

Problem 112

A particular coal contains 2.5$\%$ sulfur by mass. When this coal is burned at a power plant, the sulfur is converted into sulfur dioxide gas, which is a pollutant. To reduce sulfur dioxide emissions, calcium oxide (lime) is used. The sulfur dioxide reacts with calcium oxide to form solid calcium sulfite. (a) Write the balanced chemical equation for the reaction. (b) If the coal is burned in a power plant that uses 2000.0 tons of coal per day, what mass of calcium oxide is required daily to eliminate the sulfur dioxide? (c) How many grams of calcium sulfite does this power plant produce daily?

Md M.
Auburn University Main Campus

Problem 113

Hydrogen cyanide, HCN, is a poisonous gas. The lethal dose is approximately 300 $\mathrm{mg}$ HCN per kilogram of air when inhaled. (a) Calculate the amount of HCN that gives the lethal dose in a small laboratory room measuring $12 \times 15 \times 8.0 \mathrm{ft}$ . The density of air at $26^{\circ} \mathrm{C}$ is 0.00118 $\mathrm{g} / \mathrm{cm}^{3} .$ (b) If the HCN is formed by reaction of $\mathrm{NaCN}$ with an acid such as $\mathrm{H}_{2} \mathrm{SO}_{4}$ what mass of NaCN gives the lethal dose in the room?
$$
2 \mathrm{NaCN}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+2 \mathrm{HCN}(g)
$$
(c) HCN forms when synthetic fibers containing Orlon or Acrilan burn. Acrilan has an empirical formula of $\mathrm{CH}_{2} \mathrm{CHCN},$ so HCN is 50.9$\%$ of the formula by mass. A rug measures $12 \times 15 \mathrm{ft}$ and contains 30 oz of Acrilan fibers per square yard of carpet. If the rug burns, will a lethal dose of HCN be generated in the room? Assume that the yield of HCN from the fibers is 20$\%$ and that the carpet is 50$\%$ consumed.

Aadit S.
Numerade Educator

Problem 114

The source of oxygen that drives the internal combustion engine in an automobile is air. Air is a mixture of gases, principally $\mathrm{N}_{2}(\sim 79 \%)$ and $\mathrm{O}_{2}(\sim 20 \%) .$ In the cylinder of an automobile engine, nitrogen can react with oxygen to produce nitric oxide gas, NO. As NO is emitted from the tailpipe of the car, it can react with more oxygen to produce nitrogen dioxide gas. (a) Write balanced chemical equations for both reactions. (b) Both nitric oxide and nitrogen dioxide are pollutants that can lead to acid rain and global warming; collectively, they are called "${NO}_{x}$" gases. In $2009,$ the United States emitted an estimated 19 million tons of nitrogen dioxide into the atmosphere. How many grams of nitrogen dioxide is this? (c) The production of $\mathrm{NO}_{x}$ gases is an unwanted side reaction of the main engine combustion process that turns octane, $\mathrm{C}_{8} \mathrm{H}_{18},$ into $\mathrm{CO}_{2}$ and water. If 85$\%$ of the oxygen in an engine is used to combust octane and the remainder used to produce nitrogen dioxide, calculate how many grams of nitrogen dioxide would be produced during the combustion of 500 g of octane.

Md M.
Auburn University Main Campus

Problem 115

The thermite reaction,
$$
\mathrm{Fe}_{2} \mathrm{O}_{3}+\mathrm{Al} \rightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+\mathrm{Fe}
$$
produces so much heat that the Fe product melts. This reaction is used industrially to weld metal parts under water, where a torch cannot be employed. It is also a favorite chemical demonstration in the lecture hall (on a small scale).
(a) Balance the chemical equation for the thermite reaction, and include the proper states of matter.
(b) Calculate how many grams of aluminum are needed to completely react with 500.0 g of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ in this reaction.
(c) This reaction produces 852 kJ of heat per mole of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ reacted. How many grams of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ are needed to produce $1.00 \times 10^{4} \mathrm{kJ}$ of heat?
(d) If you performed the reverse reaction aluminum-oxide plus iron makes iron oxide plus aluminum-would that reaction have heat as a reactant or a product?

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Problem 116

One of the most bizarre reactions in chemistry is called the Ugi reaction:
$$
\begin{array}{l}{\mathrm{R}_{1} \mathrm{C}(=\mathrm{O}) \mathrm{R}_{2}+\mathrm{R}_{3}-\mathrm{NH}_{2}+\mathrm{R}_{4} \mathrm{COOH}+\mathrm{R}_{5} \mathrm{NC} \rightarrow} \\ {\mathrm{R}_{4} \mathrm{C}(=\mathrm{O}) \mathrm{N}\left(\mathrm{R}_{3}\right) \mathrm{C}\left(\mathrm{R}_{1} \mathrm{R}_{2}\right) \mathrm{C}=\mathrm{ONHR}_{5}+\mathrm{H}_{2} \mathrm{O}}\end{array}
$$
(a) Write out the balanced chemical equation for the Ugi reaction, for the case where $R=C H_{3} C H_{2} C H_{2} C H_{2} C H_{2} C H_{2}-$ (this is called the hexyl group) for all compounds. (b) What mass of the "hexyl Ugi product" would you form if 435.0 $\mathrm{mg}$ of $\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}$ was the limiting reactant?

Md M.
Auburn University Main Campus