Introduction to General, Organic and Biochemistry

Frederick A. Bettelheim, William H. Brown, Mary K. Campbell

Chapter 4

Chemical Reactions - all with Video Answers

Educators

Chapter Questions

Problem 1

Following is an unbalanced equation for photosynthesis, the process by which green plants convert carbon dioxide and water to glucose and oxygen. Balance this equation:

David Collins

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Problem 2

Balance this equation: $\mathrm{C}_{6} \mathrm{H}_{14}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g}) \longrightarrow \mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g})$

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Problem 3

Balance this equation: $\mathrm{K}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(\mathrm{aq})+\mathrm{Ca}_{3}\left(\mathrm{AsO}_{4}\right)_{2}(\mathrm{s}) \longrightarrow \mathrm{K}_{3} \mathrm{AsO}_{4}(\mathrm{aq})+\mathrm{CaC}_{2} \mathrm{O}_{4}(\mathrm{s})$

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Problem 4

When a solution of copper(II) chloride, $\mathrm{CuCl}_{2}$, is added to a solution of potassium sulfide, $\mathrm{K}_{2} \mathrm{S}$, a black precipitate of copper(II) sulfide, $\mathrm{CuS}$ forms. Write the net ionic equation for the reaction.

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Problem 5

In each equation, identify the substance that is oxidized, the substance that is reduced, the oxidizing agent, and the reducing agent:
(a) $\mathrm{Ni}^{2+}(\mathrm{aq})+\mathrm{Cr}(\mathrm{s}) \longrightarrow \mathrm{Ni}(\mathrm{s})+\mathrm{Cr}^{2+}(\mathrm{aq})$
(b) $\mathrm{CH}_{2} \mathrm{O}(\mathrm{g})+\mathrm{H}_{2}(\mathrm{g}) \longrightarrow \mathrm{CH}_{3} \mathrm{OH}(\mathrm{g})$

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Problem 6

What is (a) the molecular weight of ibuprofen, $C_{13} \mathrm{H}_{18} \mathrm{O}_{2},$ and (b) the formula weight of barium phosphate, $\mathrm{Ba}_{3}\left(\mathrm{PO}_{4}\right)_{2} ?$

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Problem 7

A person drinks $1500 .$ g of water per day. How many moles is this?

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Problem 8

We wish to weigh 2.84 mol of sodium sulfide, Na,S. How many grams is this?

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Problem 9

How many moles of $\mathrm{C}$ atoms, $\mathrm{H}$ atoms, and $\mathrm{O}$ atoms are in $2.5 \mathrm{mol}$ of glucose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} ?$

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Problem 10

How many moles of copper(I) ions, $\mathrm{Cu}^{+}$, are there in $0.062 \mathrm{g}$ of copper( $\mathrm{I}$ ) nitrate, $\mathrm{CuNO}_{3} ?$

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Problem 11

How many molecules of water, $\mathrm{H}_{2} \mathrm{O}$, are in a glass of water $(235 \mathrm{g}) ?$

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Problem 12

Pure aluminum is prepared by the electrolysis of aluminum oxide according to this equation:

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Problem 13

In the industrial synthesis of acetic acid, methanol is reacted with carbon monoxide. How many moles of $\mathrm{CO}$ are required to produce $16.6 \mathrm{mol}$ of acetic acid? $\mathrm{CH}_{3} \mathrm{OH}(\mathrm{g})+\mathrm{CO}(\mathrm{g}) \longrightarrow \mathrm{CH}_{3} \mathrm{COOH}(\ell)$

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Problem 14

Ethanol is produced industrially by the reaction of ethylene with water in the presence of an acid catalyst. How many grams of ethanol are produced from 7.24 mol of ethylene? Assume that excess water is present. $\mathrm{C}_{2} \mathrm{H}_{4}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\ell) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}(\ell)$

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Problem 15

Assume that $6.0 \mathrm{g}$ of $\mathrm{C}$ and $2.1 \mathrm{g}$ of $\mathrm{H}_{2}$ are mixed and react to form methane according to the following balanced equation: $\mathrm{C}(\mathrm{s})+2 \mathrm{H}_{2}(\mathrm{g}) \longrightarrow \mathrm{CH}_{1}(\mathrm{g})$ (a) Which is the limiting reagent, and which reactant is in excess?
(b) How many grams of $\mathrm{CH}_{4}$ are produced in the reaction?

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Problem 16

In an experiment to prepare aspirin, the theoretical yield is 153.7 g. If the actual yield is $124.3 \mathrm{g}$, what is the percent yield?

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Problem 17

Balance each equation.
(a) $\mathrm{HI}+\mathrm{NaOH} \longrightarrow \mathrm{NaI}+\mathrm{H}_{2} \mathrm{O}$
(b) $\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{H}_{2} \mathrm{S} \longrightarrow \mathrm{BaS}+\mathrm{HNO}_{3}$
(c) $\mathrm{CH}_{4}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}$
$(\mathrm{d}) \mathrm{C}_{4} \mathrm{H}_{10}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}$
(e) $\mathrm{Fe}+\mathrm{CO}_{2} \longrightarrow \mathrm{Fe}_{2} \mathrm{O}_{3}+\mathrm{CO}$

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Carlene Jimenez

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Problem 18

Balance each equation.
(a) $\mathrm{H}_{2}+\mathrm{I}_{2} \longrightarrow \mathrm{HI}$
(b) $\mathrm{Al}+\mathrm{O}_{2} \longrightarrow \mathrm{Al}_{2} \mathrm{O}_{3}$
(c) $\mathrm{Na}+\mathrm{Cl}_{2} \longrightarrow \mathrm{NaCl}$
(d) $\mathrm{Al}+\mathrm{HBr} \longrightarrow \mathrm{AlBr}_{3}+\mathrm{H}_{2}$
(e) $P+O_{2} \longrightarrow P_{2} O_{5}$

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Problem 19

If you blow carbon dioxide gas into a solution of calcium hydroxide, a milky-white precipitate of calcium carbonate forms. Write a balanced equation for the formation of calcium carbonate in this reaction.

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Problem 20

Calcium oxide is prepared by heating limestone (calcium carbonate, $\mathrm{CaCO}_{3}$ ) to a high temperature, at which point it decomposes to calcium oxide and carbon dioxide. Write a balanced equation for this preparation of calcium oxide.

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Problem 21

The brilliant white light in some firework displays is produced by burning magnesium in air. The magnesium reacts with oxygen in the air to form magnesium oxide. Write a balanced equation for this reaction.

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Problem 22

The rusting of iron is a chemical reaction of iron with oxygen in the air to form iron(III) oxide. Write a balanced equation for this reaction.

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Problem 23

When solid carbon burns in a limited supply of oxygen gas, the gas carbon monoxide, $\mathrm{CO}$ forms. This gas is deadly to humans because it combines with hemoglobin in the blood, making it impossible for the blood to transport oxygen. Write a balanced equation for the formation of carbon monoxide.

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Problem 24

Solid ammonium carbonate, $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3},$ decomposes at room temperature to form gaseous ammonia, carbon dioxide, and water. Because of the ease of decomposition and the penetrating odor of ammonia, ammonium carbonate can be used as smelling salts. Write a balanced equation for this decomposition.

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Problem 25

In the chemical test for arsenic, the gas arsine, $\mathrm{AsH}_{3},$ is prepared. When arsine is decomposed by heating, arsenic metal deposits as a mirror-like coating on the surface of a glass container and hydrogen gas, $\mathrm{H}_{2},$ is given off. Write a balanced equation for the decomposition of arsine.

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Problem 26

When a piece of aluminum metal is dropped into hydrochloric acid, HCl, hydrogen is released as a gas and a solution of aluminum chloride forms. Write a balanced equation for the reaction.

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Problem 27

In the industrial chemical preparation of chlorine, $\mathrm{Cl}_{2},$ electric current is passed through an aqueous solution of sodium chloride to give $\mathrm{Cl}_{2}(\mathrm{g})$ and $\mathrm{H}_{2}(\mathrm{g})$ The other product of this reaction is sodium hydroxide. Write a balanced equation for this reaction.

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Problem 28

Answer true or false.
(a) A net ionic equation shows only those ions that undergo chemical reaction.
(b) In a net ionic equation, the number of moles of starting material must equal the number of moles of product.
(c) A net ionic equation must be balanced by both mass and charge.
(d) As a generalization, all lithium, sodium, and potassium salts are soluble in water.
(e) As a generalization, all nitrate $\left(\mathrm{NO}_{3}^{-}\right)$ salts are soluble in water.
(f) As a generalization, most carbonate (CO $_{3}^{2-}$ ) salts are insoluble in water.
(g) Sodium carbonate, $\mathrm{Na}_{2} \mathrm{CO}_{3}$, is insoluble in water.
(h) Ammonium carbonate, $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3},$ is insoluble in water.
(i) Calcium carbonate, $\mathrm{CaCO}_{3}$, is insoluble in water.
(j) Sodium dihydrogen phosphate, $\mathrm{NaH}_{2} \mathrm{PO}_{4}$, is insoluble in water.
(k) Sodium hydroxide, $\mathrm{NaOH}$, is soluble in water.
(1) Barium hydroxide, $\mathrm{Ba}(\mathrm{OH})_{2}$, is soluble in water.

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Problem 29

Balance these net ionic equations.
(a) $\mathrm{Ag}^{+}(\mathrm{aq})+\mathrm{Br}^{-}(\mathrm{aq}) \longrightarrow \mathrm{AgBr}(\mathrm{s})$
(b) $\mathrm{Cd}^{2+}(\mathrm{aq})+\mathrm{S}^{2-}(\mathrm{aq}) \longrightarrow \mathrm{CdS}(\mathrm{s})$
(c) $\mathrm{Sc}^{3+}(\mathrm{aq})+\mathrm{SO}_{4}^{2-}(\mathrm{aq}) \longrightarrow \mathrm{Sc}_{2}\left(\mathrm{SO}_{4}\right)_{3}(\mathrm{s})$
$(d) \operatorname{Sn}^{2+}(a q)+F e^{2+}(a q) \longrightarrow \operatorname{Sn}(s)+F e^{3+}(a q)$
(e) $\mathrm{K}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\ell) \longrightarrow \mathrm{K}^{+}(\mathrm{aq})+\mathrm{OH}^{-(\mathrm{aq})}+\mathrm{H}_{2}(\mathrm{g})$

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Problem 30

In the equation
$2 \mathrm{Na}^{+}(\mathrm{aq})+\mathrm{CO}_{3}^{2-(\mathrm{aq})}+\mathrm{Sr}^{2+}(\mathrm{aq})+2 \mathrm{Cl}^{-}(\mathrm{aq}) \longrightarrow$ $\mathrm{SrCO}_{3}(\mathrm{s})+2 \mathrm{Na}^{+}(\mathrm{aq})+2 \mathrm{Cl}^{-}(\mathrm{aq})$
(a) Identify the spectator ions.
(b) Write the balanced net ionic equation.

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Problem 31

Predict whether a precipitate will form when aqueous solutions of the following compounds are mixed. If a precipitate will form, write its formula and write a net ionic equation for its formation. To make your predictions, use the solubility generalizations in Section 4-3. (a) $\mathrm{CaCl}_{2}(\mathrm{aq})+\mathrm{K}_{3} \mathrm{PO}_{4}(\mathrm{aq}) \longrightarrow$
(b) $\mathrm{KCl}(\mathrm{aq})+\mathrm{Na}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \longrightarrow$
(c) $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}(\mathrm{aq})+\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq}) \longrightarrow$
$(\mathrm{d}) \mathrm{FeCl}_{2}(\mathrm{aq})+\mathrm{KOH}(\mathrm{aq}) \longrightarrow$
(e) $\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+\mathrm{NaOH}(\mathrm{aq}) \longrightarrow$
$(f) \quad \mathrm{Na}_{2} \mathrm{S}(\mathrm{aq})+\mathrm{SbCl}_{3}(\mathrm{aq}) \longrightarrow$
$(g) P b\left(N O_{3}\right)_{2}(a q)+K_{2} S O_{4}(a q) \longrightarrow$

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Problem 32

When a solution of ammonium chloride is added to a solution of lead(II) nitrate, $\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}$, a white precipitate, lead(II) chloride, forms. Write a balanced net ionic equation for this reaction. Both ammonium chloride and lead nitrate exist as dissociated ions in aqueous solution.

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Problem 33

When a solution of ammonium chloride is added to a solution of lead(II) nitrate, $\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}$, a white precipitate, lead(II) chloride, forms. Write a balanced net ionic equation for this reaction. Both ammonium chloride and lead nitrate exist as dissociated ions in aqueous solution.

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Problem 34

When a solution of sodium hydroxide is added to a solution of ammonium carbonate, $\mathrm{H}_{2} \mathrm{O}$ is formed and ammonia gas, $\mathrm{NH}_{3}$, is released when the solution is heated. Write a net ionic equation for this reaction. Both $\mathrm{NaOH}$ and $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}$ exist as dissociated ions in aqueous solution.

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Problem 35

Using the solubility generalizations given in Section $4-3,$ predict which of these ionic compounds are soluble in water.
(a) KCl
(b) $\mathrm{NaOH}$
(c) $\mathrm{BaSO}_{4}$
$(d) \mathrm{Na}_{2} \mathrm{SO}_{4}$
(e) $\mathrm{Na}_{2} \mathrm{CO}_{3}$
$(\mathrm{f}) \mathrm{Fe}(\mathrm{OH})_{2}$

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Problem 36

Using the solubility generalizations given in Section $4-3,$ predict which of these ionic compounds are soluble in water.
(a) $\mathrm{MgCl}_{2}$
(b) $\mathrm{CaCO}_{3}$
(c) $\mathrm{Na}_{2} \mathrm{SO}_{3}$
$(d) \mathrm{NH}_{4} \mathrm{NO}_{3}$
(e) $\mathrm{Pb}(\mathrm{OH})_{2}$

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Problem 37

Answer true or false.
(a) When a substance is oxidized, it loses electrons.
(b) When a substance gains electrons, it is reduced.
(c) In a redox reaction, the oxidizing agent becomes reduced.
(d) In a redox reaction, the reducing reagent becomes oxidized.
(e) When $\mathrm{Zn}$ is converted to $\mathrm{Zn}^{2+}$ ion, zinc is oxidized.
(f) Oxidation can also be defined as the loss of oxygen atoms and/or the gain of hydrogen atoms.
(g) Reduction can also be defined as the gain of oxygen atoms and/or the loss of hydrogen atoms.
(h) When oxygen, $O_{2}$, is converted to hydrogen peroxide, $\mathrm{H}_{2} \mathrm{O}_{2},$ we say that $\mathrm{O}_{2}$ is reduced.
(i) Hydrogen peroxide, $\mathrm{H}_{2} \mathrm{O}_{2}$, is an oxidizing agent.
(j) All combustion reactions are redox reactions.
(k) The products of complete combustion (oxidation) of hydrocarbon fuels are carbon dioxide, water and heat.
(1) In the combustion of hydrocarbon fuels, oxygen is the oxidizing agent and the hydrocarbon fuel is the reducing agent.
$(\mathrm{m})$ Incomplete combustion of hydrocarbon fuels can produce significant amounts of carbon monoxide.
(n) Most common bleaches are oxidizing agents.

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Problem 38

In the reaction $\mathrm{Pb}(\mathrm{s})+2 \mathrm{Ag}^{+}(\mathrm{aq}) \longrightarrow \mathrm{Pb}^{2+}(\mathrm{aq})+2 \mathrm{Ag}(\mathrm{s})$ (a) Which species is oxidized and which is reduced? (b) Which species is the oxidizing agent and which is the reducing agent?

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Problem 39

In the reaction $\mathrm{C}_{7} \mathrm{H}_{12}(\ell)+10 \mathrm{O}_{2}(\mathrm{g}) \longrightarrow 7 \mathrm{CO}_{2}(\mathrm{g})+6 \mathrm{H}_{2} \mathrm{O}(\ell)$ (a) Which species is oxidized and which is reduced?
(b) Which species is the oxidizing agent and which is the reducing agent?

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Problem 40

When a piece of sodium metal is added to water, hydrogen is evolved as a gas and a solution of sodium hydroxide is formed.
(a) Write a balanced equation for this reaction.
(b) What is oxidized in this reaction? What is reduced?

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Problem 41

Answer true or false.
(a) Formula weight is the mass of a compound expressed in grams.
(b) 1 atomic mass unit (amu) is equal to 1 gram ( $g$ ).
(c) The formula weight of $\mathrm{H}_{2} \mathrm{O}$ is 18 amu.
(d) The molecular weight of $\mathrm{H}_{2} \mathrm{O}$ is 18 amu.
(e) The molecular weight of a covalent compound is the same as its formula weight.

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Problem 42

Calculate the formula weight of:
(a) KCl
(b) $\mathrm{Na}_{3} \mathrm{PO}_{4}$
(c) $\mathrm{Fe}(\mathrm{OH})_{2}$
(d) $\mathrm{NaAl}\left(\mathrm{SO}_{3}\right)_{2}$
(e) $\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}$
(f) $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{CO}_{3}$

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Problem 43

Calculate the molecular weight of:
(a) Sucrose, $C_{12} H_{22} O_{11}$
(b) Glycine, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{NO}_{2}$
(c) DDT, $\mathrm{C}_{14} \mathrm{H}_{9} \mathrm{Cl}_{5}$

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Problem 44

Answer true or false.
(a) The mole is a counting unit, just as a dozen is a counting unit.
(b) Avogadro's number is the number of formula units in one mole.
(c) Avogadro's number, to three significant figures, is $6.02 \times 10^{23}$ formula units per mole.
(d) $1 \mathrm{mol}$ of $\mathrm{H}_{2} \mathrm{O}$ contains $3 \times 6.02 \times 10^{23}$ formula units.
(e) $1 \mathrm{mol}$ of $\mathrm{H}_{2} \mathrm{O}$ has the same number of molecules as $1 \mathrm{mol}$ of $\mathrm{H}_{2} \mathrm{O}_{2}$
(f) The molar mass of a compound is its formula weight expressed in amu.
(g) The molar mass of $\mathrm{H}_{2} \mathrm{O}$ is $18 \mathrm{g} / \mathrm{mol}$.
(h) $1 \mathrm{mol}$ of $\mathrm{H}_{2} \mathrm{O}$ has the same molar mass as $1 \mathrm{mol}$ of $\mathrm{H}_{2} \mathrm{O}_{2}$
(i) 1 mol of ibuprofen, $C_{13} H_{18} O_{2},$ contains 33 mol of atoms.
(j) To convert moles to grams, multiply by Avogadro's number.
(k) To convert grams to moles, divide by molar mass.
(1) $1 \mathrm{mol}$ of $\mathrm{H}_{2} \mathrm{O}$ contains $1 \mathrm{mol}$ of hydrogen atoms and one mol of oxygen atoms.
$(\mathrm{m}) 1 \mathrm{mol}$ of $\mathrm{H}_{2} \mathrm{O}$ contains $2 \mathrm{g}$ of hydrogen atoms and $1 \mathrm{g}$ of oxygen atoms.
(n) 1 mole of $\mathrm{H}_{2} \mathrm{O}$ contains $18.06 \times 10^{23}$ atoms.

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Problem 45

Calculate the number of moles in:
(a) 32 g of methane, $\mathrm{CH}_{4}$
(b) $345.6 \mathrm{g}$ of nitric oxide, $\mathrm{NO}$
(c) $184.4 \mathrm{g}$ of chlorine dioxide, $\mathrm{ClO}_{2}$
(d) $720 .$ g of glycerin, $\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{3}$

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Problem 46

Calculate the number of grams in:
(a) 1.77 mol of nitrogen dioxide, $\mathrm{NO}_{2}$
(b) 0.84 mol of 2 -propanol, $C_{3} H_{8} O$ (rubbing alcohol)
(c) 3.69 mol of uranium hexafluoride, UF $_{6}$
(d) 0.348 mol of galactose, $C_{6} H_{12} O_{6}$
(e) $4.9 \times 10^{-2} \mathrm{mol}$ of vitamin $\mathrm{C}, \mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{6}$

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Problem 47

Calculate the number of moles of:
(a) $\mathrm{O}$ atoms in $18.1 \mathrm{mol}$ of formaldehyde, $\mathrm{CH}_{2} \mathrm{O}$
(b) $\mathrm{Br}$ atoms in $0.41 \mathrm{mol}$ of bromoform, $\mathrm{CHBr}_{3}$
(c) $\mathrm{O}$ atoms in $3.5 \times 10^{3} \mathrm{mol}$ of $\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}$
(d) $\mathrm{Hg}$ atoms in $87 \mathrm{g}$ of $\mathrm{HgO}$

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Problem 48

Calculate the number of moles of:
(a) $\mathrm{S}^{2-}$ ions in $6.56 \mathrm{mol}$ of $\mathrm{Na}_{2} \mathrm{S}$
(b) $\mathrm{Mg}^{2+}$ ions in $8.320 \mathrm{mol}$ of $\mathrm{Mg}_{3}\left(\mathrm{PO}_{4}\right)_{2}$
(c) acetate ions, $\mathrm{CH}_{3} \mathrm{COO}^{-},$ in $0.43 \mathrm{mol}$ of $\mathrm{Ca}\left(\mathrm{CH}_{3} \mathrm{COO}\right)_{2}$

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Problem 49

Calculate the number of:
(a) nitrogen atoms in $25.0 \mathrm{g}$ of $\mathrm{TNT}$, $\mathrm{C}_{7} \mathrm{H}_{5} \mathrm{N}_{3} \mathrm{O}_{6}$
(b) carbon atoms in $40.0 \mathrm{g}$ of ethanol, $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$
(c) oxygen atoms in $500, \mathrm{mg}$ of aspirin, $\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}$
(d) sodium atoms in 2.40 g of sodium dihydrogen phosphate, $\mathrm{NaH}_{2} \mathrm{PO}_{4}$

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Problem 50

How many molecules are in each of the following?
(a) 2.9 mol of $\mathrm{TNT}$, $\mathrm{C}_{7} \mathrm{H}_{5} \mathrm{N}_{3} \mathrm{O}_{6}$
(b) one drop $(0.0500 \mathrm{g})$ of water
(c) $3.1 \times 10^{-1} \mathrm{g}$ of aspirin, $\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}$

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Problem 51

What is the mass in grams of each number of molecules of formaldehyde, $\mathrm{CH}_{2} \mathrm{O} ?$
(a) $100 .$ molecules
(b) $3000 .$ molecules
(c) $5.0 \times 10^{6}$ molecules
(d) $2.0 \times 10^{24}$ molecules

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Problem 52

The molecular weight of hemoglobin is about 68,000 amu. What is the mass in grams of a single molecule of hemoglobin?

Narayan Hari

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Problem 53

A typical deposit of cholesterol, $\mathrm{C}_{27} \mathrm{H}_{46} \mathrm{O}$, in an artery might have a mass of 3.9 mg. How many molecules of cholesterol are in this mass?

Carlene Jimenez

Carlene Jimenez

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Problem 54

Answer true or false.
(a) Stoichiometry is the study of mass relationships in chemical reactions.
(b) To determine mass relationships in a chemical reaction, you first need to know the balanced chemical equation for the reaction.
(c) To convert from grams to moles and vice versa, use Avogadro's number as a conversion factor.
(d) To convert from grams to moles and vice versa, use molar mass as a conversion factor.
(e) A limiting reagent is the reagent that is used up first.
(f) Suppose a chemical reaction between A and B requires $1 \mathrm{mol}$ of $\mathrm{A}$ and $2 \mathrm{mol}$ of $\mathrm{B}$. If $1 \mathrm{mol}$ of each is present, then $\mathrm{B}$ is the limiting reagent.
(g) Theoretical yield is the yield of product that should be obtained according to the balanced chemical equation.
(h) Theoretical yield is the yield of product that should be obtained if all limiting reagent is converted to product.
(i) Percent yield is the number of grams of product divided by the number of grams of the limiting reagent times 100
(j) To calculate percent yield, divide the mass of product formed by the theoretical yield and multiply by 100

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Problem 55

For the reaction:
$2 \mathrm{N}_{2}(\mathrm{g})+3 \mathrm{O}_{2}(\mathrm{g}) \longrightarrow 2 \mathrm{N}_{2} \mathrm{O}_{3}(\mathrm{g})$
(a) How many moles of $\mathrm{N}_{2}$ are required to react completely with 1 mole of $\mathrm{O}_{2} ?$
(b) How many moles of $\mathrm{N}_{2} \mathrm{O}_{3}$ are produced from the complete reaction of 1 mole of $\mathrm{O}_{2} ?$
(c) How many moles of $\mathrm{O}_{2}$ are required to produce 8 moles of $\mathrm{N}_{2} \mathrm{O}_{3} ?$

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Problem 56

Magnesium reacts with sulfuric acid according to the following equation. How many moles of $\mathrm{H}_{2}$ are produced by the complete reaction of $230 .$ mg of Mg with sulfuric acid? $\mathrm{Mg}(\mathrm{s})+\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq}) \longrightarrow \mathrm{MgSO}_{4}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{g})$

Carlene Jimenez

Carlene Jimenez

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Problem 57

Chloroform, $\mathrm{CHCl}_{3}$, is prepared industrially by the reaction of methane with chlorine. How many grams of $\mathrm{Cl}_{2}$ are needed to produce 1.50 moles of chloroform? $\mathrm{CH}_{4}(\mathrm{g})+3 \mathrm{Cl}_{2}(\mathrm{g}) \longrightarrow \mathrm{CHCl}_{3}(\ell)+3 \mathrm{HCl}(\mathrm{g})$

Carlene Jimenez

Carlene Jimenez

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Problem 58

At one time, acetaldehyde was prepared industrially by the reaction of ethylene with air in the presence of a copper catalyst. How many grams of acetaldehyde can be prepared from $2 \mathrm{C}_{2} \mathrm{H}_{4}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g}) \stackrel{\text { Catalyst }}{\longrightarrow} 2 \mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}(\mathrm{g})$

David Collins

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Problem 59

Chlorine dioxide, $\mathrm{ClO}_{2}$, is used for bleaching paper It is also the gas used to kill the anthrax spores that contaminated the Hart Senate Office Building in the fall of 2001 . Chlorine dioxide is prepared by treating sodium chlorite with chlorine gas. $\mathrm{NaClO}_{2}(\mathrm{aq})+\mathrm{Cl}_{2}(\mathrm{g}) \longrightarrow \mathrm{ClO}_{2}(\mathrm{g})+\mathrm{NaCl}(\mathrm{aq})$ (a) Balance the equation for the preparation of chlorine dioxide. (b) Calculate the weight of chlorine dioxide that can be prepared from $5.50 \mathrm{kg}$ of sodium chlorite.

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Problem 60

Ethanol, $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O},$ is added to gasoline to produce "gasohol," a fuel for automobile engines. How many grams of $\mathrm{O}_{2}$ are required for complete combustion of $421 \mathrm{g}$ of ethanol? $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\ell)+3 \mathrm{O}_{2}(\mathrm{g}) \longrightarrow 2 \mathrm{CO}_{2}(\mathrm{g})+3 \mathrm{H}_{2} \mathrm{O}$

David Collins

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Problem 61

In photosynthesis, green plants convert $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ to glucose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} .$ How many grams of $\mathrm{CO}_{2}$
are required to produce $5.1 \mathrm{g}$ of glucose? $6 \mathrm{CO}_{2}(\mathrm{g})+6 \mathrm{H}_{2} \mathrm{O}(\ell) \frac{\text { Photosynthesis }}{\longrightarrow} \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(\mathrm{aq})+6 \mathrm{O}_{2}(\mathrm{g})$

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 62

Iron ore is converted to iron by heating it with coal (carbon), and oxygen according to the following equation: $2 \mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{s})+6 \mathrm{C}(\mathrm{s})+3 \mathrm{O}_{2}(\mathrm{g}) \longrightarrow 4 \mathrm{Fe}(\mathrm{s})+6 \mathrm{CO}_{2}(\mathrm{g})$ If the process is run until $3940 .$ g of $\mathrm{Fe}$ is produced, how many grams of $\mathrm{CO}_{2}$ will also be produced?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 63

Given the reaction in Problem $4-62,$ how many grams of $\mathrm{C}$ are necessary to react completely with $0.58 \mathrm{g}$ of $\mathrm{Fe}_{2} \mathrm{O}_{3} ?$

David Collins

Numerade Educator

Problem 64

Aspirin is made by the reaction of salicylic acid with acetic anhydride. How many grams of aspirin are produced if $85.0 \mathrm{g}$ of salicylic acid is treated with excess acetic anhydride?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 65

Suppose the preparation of aspirin from salicylic acid and acetic anhydride (Problem $4-64$ ) gives a yield of $75.0 \%$ of aspirin. How many grams of salicylic acid must be used to prepare $50.0 \mathrm{g}$ of aspirin?

David Collins

Numerade Educator

Problem 66

Benzene reacts with bromine to produce bromobenzene according to the following equation: $\mathrm{C}_{6} \mathrm{H}_{6}(\ell)+\mathrm{Br}_{2}(\ell) \longrightarrow \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{Br}(\ell)+\mathrm{HBr}(\mathrm{g})$ If $60.0 \mathrm{g}$ of benzene is mixed with $135 \mathrm{g}$ of bromine,
(a) Which is the limiting reagent?
(b) How many grams of bromobenzene are formed in the reaction?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 67

Ethyl chloride is prepared by the reaction of chlorine with ethane according to the following balanced equation. $\mathrm{C}_{2} \mathrm{H}_{6}(\mathrm{g})+\mathrm{Cl}_{2}(\mathrm{g}) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}(\ell)+\mathrm{HCl}(\mathrm{g})$ When $5.6 \mathrm{g}$ of ethane is reacted with excess chlorine, $8.2 \mathrm{g}$ of ethyl chloride forms, Calculate the percent yield of ethyl chloride.

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 68

Diethyl ether is made from ethanol according to the following reaction:
$$
2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}(\ell) \longrightarrow\left(\mathrm{C}_{2} \mathrm{H}_{5}\right)_{2} \mathrm{O}(\ell)+\mathrm{H}_{2} \mathrm{O}(\ell)
$$
In an experiment, $517 \mathrm{~g}$ of ethanol gave $391 \mathrm{~g}$ of diethyl ether. What was the percent yield in this experiment?

David Collins

Numerade Educator

Problem 69

Answer true or false.
(a) Heat of reaction is the heat given off or absorbed by a chemical reaction.
(b) An endothermic reaction is one that gives off heat.
(c) If a chemical reaction is endothermic, the reverse reaction is exothermic.
(d) All combustion reactions are exothermic.
(e) If the reaction of glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ and $\mathrm{O}_{2}$ in the body to give $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ is an exothermic reaction, then photosynthesis in green plants (the reaction of $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$ to give glucose and $\mathrm{O}_{2}$, is an endothermic process.
(f) The energy required to drive photosynthesis comes from the sun in the form of electromagnetic radiation.

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 70

What is the difference between exothermic and endothermic reactions?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 71

Which of these reactions are exothermic, and which are endothermic?
(a) $2 \mathrm{NH}_{3}(\mathrm{g})+22.0 \mathrm{kcal} \longrightarrow \mathrm{N}_{2}(\mathrm{g})+3 \mathrm{H}_{2}(\mathrm{g})$
(b) $\mathrm{H}_{2}(\mathrm{g})+\mathrm{F}_{2}(\mathrm{g}) \longrightarrow 2 \mathrm{HF}(\mathrm{g})+124$ kcal
(c) $\mathrm{C}(\mathrm{s})+\mathrm{O}_{2}(\mathrm{g}) \longrightarrow \mathrm{CO}_{2}(\mathrm{g})+94.0 \mathrm{kcal}$
$(\mathrm{d}) \mathrm{H}_{2}(\mathrm{g})+\mathrm{CO}_{2}(\mathrm{g})+9.80 \mathrm{kcal} \longrightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+\mathrm{CO}(\mathrm{g})$
(e) $\mathrm{C}_{3} \mathrm{H}_{8}(\mathrm{g})+5 \mathrm{O}_{2}(\mathrm{g}) \longrightarrow 3 \mathrm{CO}_{2}(\mathrm{g})+$\[4 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+531 \mathrm{kcal}\]

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 72

In the following reaction, 9.80 kcal is absorbed per mole of $\mathrm{CO}_{2}$ undergoing reaction. How much heat is given off if two moles of water are reacted with two moles of carbon monoxide?
$\mathrm{H}_{2}(\mathrm{g})+\mathrm{CO}_{2}(\mathrm{g})+9.80 \mathrm{kcal} \longrightarrow \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+\mathrm{CO}(\mathrm{g})$

David Collins

Numerade Educator

Problem 73

Following is the equation for the combustion of acetone: $2 \mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}(\ell)+8 \mathrm{O}_{2}(\mathrm{g}) \longrightarrow 6 \mathrm{CO}_{2}(\mathrm{g})+$
Acetone $6 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+853.6 \mathrm{kcal}$

David Collins

Numerade Educator

Problem 74

The oxidation of glucose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$, to carbon dioxide and water is exothermic. The heat liberated is the same whether glucose is metabolized in the body or burned in air.
$$
\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+6 \mathrm{O}_{2} \longrightarrow 6 \mathrm{CO}_{2}+6 \mathrm{H}_{2} \mathrm{O}+670 \mathrm{kcal} / \mathrm{mol}
$$
Calculate the heat liberated when $15.0 \mathrm{~g}$ of glucose is metabolized to carbon dioxide and water in the body.

David Collins

Numerade Educator

Problem 75

The heat of combustion of glucose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$, is $670 \mathrm{kcal} / \mathrm{mol} .$ The heat of combustion of ethanol, $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O},$ is $327 \mathrm{kcal} / \mathrm{mol}$. The heat liberated by oxidation
of each compound is the same whether it is burned in air or metabolized in the body. On a kcal/g basis, metabolism of which compound liberates more heat?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 76

A plant requires approximately 4178 kcal for the production of $1.00 \mathrm{kg}$ of starch (Chapter 20 ) from carbon dioxide and water
(a) Is the production of starch in a plant an exothermic process or an endothermic process?
(b) Calculate the energy in kilocalories required by a plant for the production of 6.32 g of starch.

David Collins

Numerade Educator

Problem 77

To convert 1 mol of iron(III) oxide to its elements requires 196.5 kcal: $\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{s})+196.5 \mathrm{kcal} \longrightarrow 2 \mathrm{Fe}(\mathrm{s})+\frac{3}{2} \mathrm{O}_{2}(\mathrm{g})$ Which electrode is the anode, and which is the cathode?

David Collins

Numerade Educator

Problem 78

(Chemical Connections 4 A) How does fluoride ion protect the tooth enamel against decay?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 79

(Chemical Connections 4 A) What ions are present in hydroxyapatite?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 80

(Chemical Connections $4 \mathrm{B}$ ) A voltaic cell is represented by the following equation:
$\mathrm{Fe}(\mathrm{s})+\mathrm{Zn}^{2+}(\mathrm{aq}) \longrightarrow \mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{Zn}(\mathrm{s})$
Which electrode is the anode, and which is the cathode?

David Collins

Numerade Educator

Problem 81

(Chemical Connections $4 \mathrm{C}$ ) Balance the lithiumiodine battery redox reaction described in this section and identify the oxidizing and reducing agents present.

David Collins

Numerade Educator

Problem 82

When gaseous dinitrogen pentoxide, $\mathrm{N}_{2} \mathrm{O}_{5},$ is bubbled into water, nitric acid, $\mathrm{HNO}_{3}$, forms. Write a balanced equation for this reaction.

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 83

In a certain reaction, $\mathrm{Cu}^{+}$ is converted to $\mathrm{Cu}^{2+}$. Is $\mathrm{Cu}^{+}$ ion oxidized or reduced in this reaction? Is $\mathrm{Cu}^{+}$ ion an oxidizing agent or a reducing agent in this reaction?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 84

Using the equation: $\mathrm{Fe}_{2} \mathrm{O}_{3}(\mathrm{s})+3 \mathrm{CO}(\mathrm{g}) \longrightarrow 2 \mathrm{Fe}(\mathrm{s})+3 \mathrm{CO}_{2}(\mathrm{g})$ (a) Show that this is a redox reaction. Which species is oxidized, and which is reduced?
(b) How many moles of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ are required to produce 38.4 mol of Fe?
(c) How many grams of CO are required to produce $38.4 \mathrm{mol}$ of $\mathrm{Fe} ?$

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 85

Methyl tertiary butyl ether (or MTBE), a chemical compound with molecular formula $\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O},$ is an additive used as an oxygenate to raise the octane number of gas, although its use has declined in the last few years in response to environmental and health concerns. Write the balanced molecular equation for the reaction involving the complete burning of liquid MTBE in air

David Collins

Numerade Educator

Problem 86

When an aqueous solution of $\mathrm{Na}_{3} \mathrm{PO}_{4}$ is added to an aqueous solution of $\mathrm{Cd}\left(\mathrm{NO}_{3}\right)_{2},$ a precipitate forms. Write a net ionic equation for this reaction and identify the spectator ions.

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 87

The active ingredient in an analgesic tablet is $488 \mathrm{mg}$ of aspirin, $\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{5}$. How many moles of aspirin does the tablet contain?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 88

Chlorophyll, the compound responsible for the green color of leaves and grasses, contains one atom of magnesium in each molecule. If the percentage by weight of magnesium in chlorophyll is $2.72 \%,$ what is the molecular weight of chlorophyll?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 89

If $7.0 \mathrm{kg}$ of $\mathrm{N}_{2}$ is added to $11.0 \mathrm{kg}$ of $\mathrm{H}_{2}$ to form $\mathrm{NH}_{3}$ which reactant is in excess? $\mathrm{N}_{2}(\mathrm{g})+3 \mathrm{H}_{2}(\mathrm{g}) \longrightarrow 2 \mathrm{NH}_{3}(\mathrm{g})$

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 90

Lead(II) nitrate and aluminum chloride react according to the following equation: $3 \mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}+2 \mathrm{AlCl}_{3} \longrightarrow 3 \mathrm{PbCl}_{2}+2 \mathrm{Al}\left(\mathrm{NO}_{3}\right)$ In an experiment, 8.00 g of lead nitrate reacted with $2.67 \mathrm{g}$ of aluminum chloride to give $5.55 \mathrm{g}$ of lead chloride.
(a) Which reactant was the limiting reagent?
(b) What was the percent yield?

David Collins

Numerade Educator

Problem 91

Assume that the average red blood cell has a mass of $2 \times 10^{-8} \mathrm{g}$ and that $20 \%$ of its mass is hemoglobin (a protein whose molar mass is 68,000 ). How many molecules of hemoglobin are present in one red blood cell?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 92

Reaction of pentane, $C_{5} H_{12},$ with oxygen, $O_{2},$ gives carbon dioxide and water.
(a) Write a balanced equation for this reaction.
(b) In this reaction, what is oxidized and what is reduced?
(c) What is the oxidizing agent, and what is the reducing agent?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 93

Ammonia is prepared industrially by the reaction of nitrogen and hydrogen according to the following equation: $\mathrm{N}_{2}(\mathrm{g})+3 \mathrm{H}_{2}(\mathrm{g}) \longrightarrow 2 \mathrm{NH}_{3}(\mathrm{g})$ If $29.7 \mathrm{kg}$ of $\mathrm{N}_{2}$ is added to $3.31 \mathrm{kg}$ of $\mathrm{H}_{2}$
(a) Which reactant is the limiting reagent?
(b) How many grams of the other reactant are left over?
(c) How many grams of $\mathrm{NH}_{3}$ are formed if the reaction goes to completion?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 94

2,3,7,8 -Tetrachlorodibenzo-p-dioxin (TCDD) is a potent poison with the chemical formula $\mathrm{C}_{12} \mathrm{H}_{4} \mathrm{Cl}_{4} \mathrm{O}_{2}$ The average lethal dose in humans is approximately $2.9 \times 10^{-2} \mathrm{mg}$ per kg of body weight. How many molecules of TCDD constitute a lethal dose for an 82-kg individual?

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 95

Furan, an organic compound used in the synthesis of nylon and referenced in Section $20-2,$ has the molecular formula $\mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}$
(a) Determine the number of moles of furan in a $441 \mathrm{mg}$ sample
(b) If the density of furan is known to be $0.936 \mathrm{g} / \mathrm{mL}$ how many carbon atoms are present in $0.060 \mathrm{L}$ of furan?
(c) Calculate the mass in grams of $9.86 \times 10^{25}$ molecules of furan.

David Collins

Numerade Educator

Problem 96

A sample of gold consisting of $8.68 \times 10^{23}$ atoms with a density of $19.3 \mathrm{g} / \mathrm{mL}$ is hammered into a sheet that covers an area of $1.00 \times 10^{2} \mathrm{ft}^{2}$. Determine the thickness of the sheet in centimeters.

David Collins

Numerade Educator

Problem 97

Consider the production of $\mathrm{KClO}_{4}(a q)$ via the three balanced sequential reactions below, where the percentage yield of each reaction is written above the reaction arrows: Determine the mass in grams of $\mathrm{KClO}_{4}(\text { aq })$ produced at the end of the three-step reaction sequence if a student begins with $966 \mathrm{kg}$ of $\mathrm{Cl}_{2}(\mathrm{g})$

David Collins

Numerade Educator

Problem 98

Elemental chlorine is commonly used to kill microorganisms in drinking water supplies as well as to remove sulfides. For example, noxious-smelling hydrogen sulfide gas is removed from water via the following unbalanced chemical equation: $\mathrm{H}_{2} \mathrm{S}(\mathrm{aq})+\mathrm{Cl}_{2}(\mathrm{aq}) \longrightarrow \mathrm{HCl}(\mathrm{aq})+\mathrm{S}_{8}(\mathrm{s})$ (a) Write a balanced equation for this reaction. (b) Determine the mass in grams of elemental sulfur, $S_{8},$ which is produced when 50.0 L of water containing $1.5 \times 10^{-5} \mathrm{g}$ of $\mathrm{H}_{2} \mathrm{S}$ per liter is treated with $1.0 \mathrm{g}$ of $\mathrm{Cl}_{2}$
(c) Calculate the percent yield of the reaction if $5.8 \times 10^{-4} \mathrm{g}$ of $\mathrm{S}_{8}$ is generated.

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 99

The two major sources of energy in our diets are fats and carbohydrates. Palmitic acid, one of the major components of both animal fats and vegetable oils, belongs to a group of compounds called fatty acids. The metabolism of fatty acids is responsible for the energy from fats. The major carbohydrates in our diets are sucrose (table sugar; Section 20-4A) and starch (Section 20-5A). Both starch and sucrose are first converted in the body to glucose, and then glucose is metabolized to produce energy. The heat of combustion of palmitic acid is 2385 kcal/mol, and that of glucose is $670 .$ kcal/mol. Below are unbalanced equations for the metabolism of each body fuel: $\mathrm{C}_{16} \mathrm{H}_{32} \mathrm{O}_{2}(\mathrm{aq})+\mathrm{O}_{2}(\mathrm{g}) \longrightarrow$ $\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\ell)+2385 \mathrm{kcal} / \mathrm{mol}$ $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}(\mathrm{aq})+\mathrm{O}_{2}(\mathrm{g}) \longrightarrow$ $\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\ell)+670 \mathrm{kcal} / \mathrm{mol}$ (a) Balance the equation for the metabolism of each fuel.
(b) Calculate the heat of combustion of each in kcal/g.
(c) In terms of kcal/mol, which of the two is the better source of energy for the body?
(d) In terms of kcal/g, which of the two is the better source of energy for the body?

David Collins

Numerade Educator

Problem 100

The heat of combustion of methane, $\mathrm{CH}_{4}$, the major component of natural gas, is 213 kcal/mol. The heat of combustion of propane, $\mathrm{C}_{3} \mathrm{H}_{8},$ the major component of LPG, or bottled gas, is $530 .$ kcal/mol.
(a) Write a balanced equation for the complete combustion of each to $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$
(b) $\mathrm{O}_{\mathrm{n}}$ a kcal/mol basis, which of these two fuels is the better source of heat energy?
(c) $\mathrm{On}$ a keal/g basis, which of these two fuels is the better source of heat energy?

David Collins

Numerade Educator

Problem 101

An automobile with gasoline consisting of octane, $\mathrm{C}_{8} \mathrm{H}_{18}(\ell),$ has a density of $0.69 \mathrm{g} / \mathrm{mL}$. If the auto-
mobile travels 168 miles with a gas mileage of $21.2 \mathrm{mi} / \mathrm{gal},$ how many $\mathrm{kg}$ of $\mathrm{CO}_{2}$ are produced assuming complete combustion of octane and excess oxygen?

David Collins

Numerade Educator

Problem 102

Aspartame, an artificial sweetener used as a sugar substitute in some foods and beverages, has the molecular formula $\mathrm{C}_{14} \mathrm{H}_{18} \mathrm{N}_{2} \mathrm{O}_{5}$
(a) How many mg of aspartame are present in $3.72 \times 10^{26}$ molecules of aspartame?
(b) Imagine you obtain $25.0 \mathrm{mL}$ of aspartame, which is known to have a density of $1.35 \mathrm{g} / \mathrm{mL}$. How many molecules of aspartame are present in this volume?
(c) How many hydrogen atoms are present in $1.00 \mathrm{mg}$ of aspartame?
(d) Complete the skeletal structure of aspartame, where all the bonded atoms are shown but double bonds, triple bonds, and/or lone pairs are missing. (e) Identify the various types of geometries present in each central atom of aspartame using VSEPR theory.
(f) Determine the various relative bond angles associated with each central atom of aspartame using VSEPR theory.
(g) What is the most polar bond in aspartame?
(h) Would you predict aspartame to be polar or nonpolar?
(i) Is aspartame expected to possess resonance? Explain why or why not.
(j) Consider the combustion of aspartame, which results in formation of $\mathrm{NO}_{2}(\mathrm{g})$ as well as other expected products. Write a balanced chemical equation for this reaction.
(k) Calculate the weight of $\mathrm{CO}_{2}(\mathrm{g})$ that can be prepared from $1.62 \mathrm{g}$ of aspartame mixed with $2.11 \mathrm{g}$ of oxygen gas.

Carlene Jimenez

Carlene Jimenez

Numerade Educator

Problem 103

Caffeine, a central nervous system stimulant, has the molecular formula $\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{4} \mathrm{O}_{2}$
(a) How many moles of caffeine are present in $6.19 \times 10^{25}$ molecules of caffeine? (b) Imagine you dissolve caffeine in water to a volume of $100.0 \mathrm{mL},$ which is known to have a density of $1.23 \mathrm{g} / \mathrm{mL}$. How many molecules of caffeine are present in this volume?
(c) How many nitrogen atoms are present in $3.5 \mathrm{mg}$ of caffeine?
(d) Complete the skeletal structure of caffeine, where all the bonded atoms are shown but double bonds, triple bonds, and/or lone pairs are missing. (e) Identify the various types of geometries present in each central atom of caffeine using VSEPR theory.
(f) Determine the various relative bond angles associated with each central atom of caffeine using VSEPR theory.
(g) What is the most polar bond in caffeine?
(h) Would you predict caffeine to be polar or nonpolar?
(i) Consider the combustion of caffeine, which results in formation of $\mathrm{NO}_{2}(\mathrm{g})$ as well as other expected products. Write a balanced chemical equation for this reaction.
(j) The heat of combustion for caffeine is $2211 \mathrm{kcal} / \mathrm{mol} .$ How much heat will be given off if $0.81 \mathrm{g}$ of caffeine is burned completely?
(k) Calculate the weight of $\mathrm{H}_{2} \mathrm{O}(\mathrm{g})$ that can be prepared from 8.00 g of caffeine mixed with $20.3 \mathrm{g}$ of oxygen gas.

Carlene Jimenez

Carlene Jimenez

Numerade Educator