CHEMISTRY: The Molecular Nature of Matter and Change

Martin S. Silberberg, Patricia G. Amateis

Chapter 3

Stoichiometry of Formulas and Equations - all with Video Answers

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Chapter Questions

Problem 1

The atomic mass of $\mathrm{Cl}$ is 35.45 amu, and the atomic mass of Al is 26.98 amu. What are the masses in grams of 3 mol of Al atoms and of $2 \mathrm{~mol}$ of $\mathrm{Cl}$ atoms?

Stephen Ho

Stephen Ho

Numerade Educator

Problem 2

(a) How many moles of $\mathrm{C}$ atoms are in $1 \mathrm{~mol}$ of sucrose $\left(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\right) ?$
(b) How many C atoms are in $2 \mathrm{~mol}$ of sucrose?

Stephen Ho

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Problem 3

Why might the expression " 1 mol of chlorine" be confusing? What change would remove any uncertainty? For what other elements might a similar confusion exist? Why?

Stephen Ho

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Problem 4

How is the molecular mass of a compound the same as the molar mass, and how is it different?

Stephen Ho

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Problem 5

What advantage is there to using a counting unit (the mole), rather than a mass unit, for amount of substance?

Stephen Ho

Numerade Educator

Problem 6

You need to calculate the number of $\mathrm{P}_{4}$ molecules that can form from $2.5 \mathrm{~g}$ of $\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2} .$ Draw a road map for solving this and write a plan, without doing any calculations.

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 7

Each of the following balances weighs the indicated numbers of atoms of two elements:
For each balance, which element-left, right, or neither
(a) Has the higher molar mass?
(b) Has more atoms per gram?
(c) Has fewer atoms per gram?
(d) Has more atoms per mole?

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 8

Calculate the molar mass of each of the following:
(a) $\operatorname{Sr}(\mathrm{OH})_{2}$
(b) $\mathrm{N}_{2} \mathrm{O}_{3}$
(c) $\mathrm{NaClO}_{3}$
(d) $\mathrm{Cr}_{2} \mathrm{O}_{3}$

Stephen Ho

Numerade Educator

Problem 9

Calculate the molar mass of each of the following:
(a) $\left(\mathrm{NH}_{4}\right)_{3} \mathrm{PO}_{4}$
(b) $\mathrm{CH}_{2} \mathrm{Cl}_{2}$
(c) $\mathrm{CuSO}_{4} \cdot 5 \mathrm{H}_{2} \mathrm{O}$
(d) $\mathrm{BrF}_{3}$

Stephen Ho

Numerade Educator

Problem 10

Calculate the molar mass of each of the following:
(a) $\mathrm{SnO}$
(b) $\mathrm{BaF}_{2}$
(c) $\mathrm{Al}_{2}\left(\mathrm{SO}_{4}\right)_{3}$
(d) $\mathrm{MnCl}_{2}$

Stephen Ho

Numerade Educator

Problem 11

Calculate the molar mass of each of the following:
(a) $\mathrm{N}_{2} \mathrm{O}_{4}$
(b) $\mathrm{C}_{4} \mathrm{H}_{9} \mathrm{OH}$
(c) $\mathrm{MgSO}_{4} \cdot 7 \mathrm{H}_{2} \mathrm{O}$
(d) $\mathrm{Ca}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{2}$

Stephen Ho

Numerade Educator

Problem 12

Calculate each of the following quantities:
(a) Mass (g) of $0.346 \mathrm{~mol}$ of $\mathrm{Zn}$
(b) Number of $\mathrm{F}$ atoms in $2.62 \mathrm{~mol}$ of $\mathrm{F}_{2}$
(c) Number of Ca atoms in $28.5 \mathrm{~g}$ of Ca

Stephen Ho

Numerade Educator

Problem 13

Calculate each of the following quantities:
(a) Amount (mol) of Mn atoms in $62.0 \mathrm{mg}$ of Mn
(b) Amount (mol) for $1.36 \times 10^{22}$ atoms of $\mathrm{Cu}$
(c) Mass (g) of $8.05 \times 10^{24} \mathrm{Li}$ atoms

Stephen Ho

Numerade Educator

Problem 14

Calculate each of the following quantities:
(a) Mass (g) of $0.68 \mathrm{~mol}$ of $\mathrm{KMnO}_{4}$
(b) Amount (mol) of O atoms in $8.18 \mathrm{~g}$ of $\mathrm{Ba}\left(\mathrm{NO}_{3}\right)_{2}$
(c) Number of $\mathrm{O}$ atoms in $7.3 \times 10^{-3} \mathrm{~g}$ of $\mathrm{CaSO}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}$

Stephen Ho

Numerade Educator

Problem 15

Calculate each of the following quantities:
(a) Mass $(\mathrm{kg})$ of $4.6 \times 10^{21}$ molecules of $\mathrm{NO}_{2}$
(b) Amount (mol) of Cl atoms in $0.0615 \mathrm{~g}$ of $\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{Cl}_{2}$
(c) Number of $\mathrm{H}^{-}$ ions in $5.82 \mathrm{~g}$ of $\mathrm{SrH}_{2}$

Stephen Ho

Numerade Educator

Problem 16

Calculate each of the following quantities:
(a) Mass $(\mathrm{g})$ of $6.44 \times 10^{-2} \mathrm{~mol}$ of $\mathrm{MnSO}_{4}$
(b) Amount (mol) of compound in $15.8 \mathrm{~kg}$ of $\mathrm{Fe}\left(\mathrm{ClO}_{4}\right)_{3}$
(c) Number of $\mathrm{N}$ atoms in $92.6 \mathrm{mg}$ of $\mathrm{NH}_{4} \mathrm{NO}_{2}$

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 17

Calculate each of the following quantities:
(a) Total number of ions in $38.1 \mathrm{~g}$ of $\mathrm{SrF}_{2}$
(b) Mass (kg) of $3.58 \mathrm{~mol}$ of $\mathrm{CuCl}_{2} \cdot 2 \mathrm{H}_{2} \mathrm{O}$
(c) Mass (mg) of $2.88 \times 10^{22}$ formula units of $\mathrm{Bi}\left(\mathrm{NO}_{3}\right)_{3} \cdot 5 \mathrm{H}_{2} \mathrm{O}$

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 18

Calculate each of the following quantities:
(a) Mass (g) of $8.35 \mathrm{~mol}$ of copper(I) carbonate
(b) Mass (g) of $4.04 \times 10^{20}$ molecules of dinitrogen pentoxide
(c) Amount (mol) and number of formula units in $78.9 \mathrm{~g}$ of sodium perchlorate
(d) Number of sodium ions, perchlorate ions, chlorine atoms, and oxygen atoms in the mass of compound in part (c)

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 19

Calculate each of the following quantities:
(a) Mass (g) of 8.42 mol of chromium(III) sulfate decahydrate
(b) Mass (g) of $1.83 \times 10^{24}$ molecules of dichlorine heptoxide
(c) Amount (mol) and number of formula units in $6.2 \mathrm{~g}$ of lithium sulfate
(d) Number of lithium ions, sulfate ions, sulfur atoms, and oxygen atoms in the mass of compound in part (c)

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 20

Calculate each of the following:
(a) Mass \% of $\mathrm{H}$ in ammonium bicarbonate
(b) Mass \% of O in sodium dihydrogen phosphate heptahydrate

Stephen Ho

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Problem 21

Calculate each of the following:
(a) Mass \% of I in strontium periodate
(b) Mass \% of Mn in potassium permanganate

Stephen Ho

Numerade Educator

Problem 22

Calculate each of the following:
(a) Mass fraction of $\mathrm{C}$ in cesium acetate
(b) Mass fraction of $\mathrm{O}$ in uranyl sulfate trihydrate (the uranyl ion is $\mathrm{UO}_{2}^{2+}$ )

Stephen Ho

Numerade Educator

Problem 23

Calculate each of the following:
(a) Mass fraction of $\mathrm{Cl}$ in calcium chlorate
(b) Mass fraction of $\mathrm{N}$ in dinitrogen trioxide

Stephen Ho

Numerade Educator

Problem 24

Oxygen is required for the metabolic combustion of foods. Calculate the number of atoms in $38.0 \mathrm{~g}$ of oxygen gas, the amount absorbed from the lungs in about 15 min when a person is at rest.

Stephen Ho

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Problem 25

Cisplatin (right), or Platinol, is used in the treatment of certain cancers. Calculate (a) the amount (mol) of compound in $285.3 \mathrm{~g}$ of cisplatin; (b) the number of hydrogen atoms in $0.98 \mathrm{~mol}$ of cisplatin.

Stephen Ho

Numerade Educator

Problem 26

Allyl sulfide (below) gives garlic its characteristic odor. Calculate (a) the mass (g) of 2.63 mol of allyl sulfide; (b) the number of carbon atoms in $35.7 \mathrm{~g}$ of allyl sulfide.

Stephen Ho

Numerade Educator

Problem 27

Iron reacts slowly with oxygen and water to form a compound commonly called rust $\left(\mathrm{Fe}_{2} \mathrm{O}_{3} \cdot 4 \mathrm{H}_{2} \mathrm{O}\right) .$ For $45.2 \mathrm{~kg}$ of rust, calculate
(a) moles of compound; (b) moles of $\mathrm{Fe}_{2} \mathrm{O}_{3} ;$ (c) grams of Fe.

Stephen Ho

Numerade Educator

Problem 28

Propane is widely used in liquid form as a fuel for barbecue grills and camp stoves. For $85.5 \mathrm{~g}$ of propane, calculate (a) moles of compound; (b) grams of carbon.

Stephen Ho

Numerade Educator

Problem 29

The effectiveness of a nitrogen fertilizer is determined mainly by its mass $\%$ N. Rank the following fertilizers, most effective first: potassium nitrate; ammonium nitrate; ammonium sulfate; urea, $\mathrm{CO}\left(\mathrm{NH}_{2}\right)_{2}$.

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 30

The mineral galena is composed of lead(II) sulfide and has an average density of $7.46 \mathrm{~g} / \mathrm{cm}^{3}$. (a) How many moles of lead(II) sulfide are in $1.00 \mathrm{ft}^{3}$ of galena?
(b) How many lead atoms are in $1.00 \mathrm{dm}^{3}$ of galena?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 31

Hemoglobin, a protein in red blood cells, carries $\mathrm{O}_{2}$. from the lungs to the body's cells. Iron (as ferrous ion, $\mathrm{Fe}^{2+}$ ) makes up 0.33 mass $\%$ of hemoglobin. If the molar mass of hemoglobin is $6.8 \times 10^{4} \mathrm{~g} / \mathrm{mol},$ how many
$\mathrm{Fe}^{2+}$ ions are in one molecule?

Stephen Ho

Numerade Educator

Problem 32

What is the difference between an empirical formula and a molecular formula? Can they ever be the same?

Stephen Ho

Numerade Educator

Problem 33

List three ways compositional data may be given in a problem that involves finding an empirical formula.

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 34

Which of the following sets of information allows you to obtain the molecular formula of a covalent compound? In each case that allows it, explain how you would proceed (draw a road map and write a plan for a solution).
(a) Number of moles of each type of atom in a given sample of the compound
(b) Mass \% of each element and the total number of atoms in a molecule of the compound
(c) Mass \% of each element and the number of atoms of one element in a molecule of the compound
(d) Empirical formula and mass $\%$ of each element
(e) Structural formula

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 35

Is $\mathrm{MgCl}_{2}$ an empirical or a molecular formula for magnesium chloride? Explain.

Stephen Ho

Numerade Educator

Problem 36

What are the empirical formula and empirical formula mass for each of the following compounds?
(a) $\mathrm{C}_{2} \mathrm{H}_{4}$
(b) $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}_{2}$
(c) $\mathrm{N}_{2} \mathrm{O}_{5}$
(d) $\mathrm{Ba}_{3}\left(\mathrm{PO}_{4}\right)_{2}$
(e) $\mathrm{Te}_{4} \mathrm{I}_{16}$

Stephen Ho

Numerade Educator

Problem 37

What are the empirical formula and empirical formula mass for each of the following compounds?
(a) $\mathrm{C}_{4} \mathrm{H}_{8}$
(b) $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}_{3}$
(c) $\mathrm{P}_{4} \mathrm{O}_{10}$
(d) $\mathrm{Ga}_{2}\left(\mathrm{SO}_{4}\right)_{3}$
(e) $\mathrm{Al}_{2} \mathrm{Br}_{6}$

Stephen Ho

Numerade Educator

Problem 38

Give the name, empirical formula, and molar mass of the compound depicted in Figure $\mathrm{P} 3.38$.

Shaelyn Deal

Numerade Educator

Problem 39

Give the name, empirical formula, and molar mass of the compound depicted in Figure $\mathrm{P} 3.39$.

Shaelyn Deal

Numerade Educator

Problem 40

What is the molecular formula of each compound?
(a) Empirical formula $\mathrm{CH}_{2}(\mathscr{A}=42.08 \mathrm{~g} / \mathrm{mol})$
(b) Empirical formula $\mathrm{NH}_{2}(\mathscr{M}=32.05 \mathrm{~g} / \mathrm{mol})$
(c) Empirical formula $\mathrm{NO}_{2}(\mathscr{M}=92.02 \mathrm{~g} / \mathrm{mol})$
(d) Empirical formula CHN $(\mathscr{M}=135.14 \mathrm{~g} / \mathrm{mol})$

Stephen Ho

Numerade Educator

Problem 41

What is the molecular formula of each compound?
(a) Empirical formula $\mathrm{CH}(\mathscr{M}=78.11 \mathrm{~g} / \mathrm{mol})$
(b) Empirical formula $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}_{2}(\mathscr{M}=74.08 \mathrm{~g} / \mathrm{mol})$
(c) Empirical formula $\mathrm{HgCl}(\mathscr{M}=472.1 \mathrm{~g} / \mathrm{mol})$
(d) Empirical formula $\mathrm{C}_{7} \mathrm{H}_{4} \mathrm{O}_{2}(\mathscr{A}=240.20 \mathrm{~g} / \mathrm{mol})$

Stephen Ho

Numerade Educator

Problem 42

Find the empirical formula of each of the following compounds: (a) 0.063 mol of chlorine atoms combined with $0.22 \mathrm{~mol}$ of oxygen atoms; (b) $2.45 \mathrm{~g}$ of silicon combined with $12.4 \mathrm{~g}$ of chlorine; (c) 27.3 mass \% carbon and 72.7 mass \% oxygen

Shaelyn Deal

Numerade Educator

Problem 43

Find the empirical formula of each of the following compounds: (a) $0.039 \mathrm{~mol}$ of iron atoms combined with $0.052 \mathrm{~mol}$ of oxygen atoms; (b) $0.903 \mathrm{~g}$ of phosphorus combined with $6.99 \mathrm{~g}$ of bromine; (c) a hydrocarbon with 79.9 mass \% carbon

Shaelyn Deal

Numerade Educator

Problem 44

An oxide of nitrogen contains 30.45 mass $\%$ N. (a) What is the empirical formula of the oxide? (b) If the molar mass is $90 \pm 5 \mathrm{~g} / \mathrm{mol},$ what is the molecular formula?

Stephen Ho

Numerade Educator

Problem 45

A chloride of silicon contains 79.1 mass $\%$ Cl. (a) What is the empirical formula of the chloride? (b) If the molar mass is $269 \mathrm{~g} / \mathrm{mol},$ what is the molecular formula?

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 46

A sample of $0.600 \mathrm{~mol}$ of a metal $\mathrm{M}$ reacts completely with excess fluorine to form $46.8 \mathrm{~g}$ of $\mathrm{MF}_{2}$.
(a) How many moles of $\mathrm{F}$ are in the sample of $\mathrm{MF}_{2}$ that forms?
(b) How many grams of $\mathrm{M}$ are in this sample of $\mathrm{MF}_{2} ?$
(c) What element is represented by the symbol M?

Shaelyn Deal

Numerade Educator

Problem 47

A 0.370 -mol sample of a metal oxide $\left(\mathrm{M}_{2} \mathrm{O}_{3}\right)$ weighs $55.4 \mathrm{~g}$.
(a) How many moles of $\mathrm{O}$ are in the sample?
(b) How many grams of $\mathrm{M}$ are in the sample?
(c) What element is represented by the symbol M?

Stephen Ho

Numerade Educator

Problem 48

Menthol $(\mathscr{A} \ell=156.3 \mathrm{~g} / \mathrm{mol}),$ the strong-smelling substance in many cough drops, is a compound of carbon, hydrogen, and oxygen. When $0.1595 \mathrm{~g}$ of menthol was burned in a combustion apparatus, $0.449 \mathrm{~g}$ of $\mathrm{CO}_{2}$ and $0.184 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$ formed. What is menthol's molecular formula?

Stephen Ho

Numerade Educator

Problem 49

The compound dimethyl phthalate, used in insect repellants, is composed of carbon, hydrogen, and oxygen and has a molar mass of $194.2 \mathrm{~g} / \mathrm{mol} .$ A $0.2572-\mathrm{g}$ sample of the compound was burned in a combustion apparatus and $0.583 \mathrm{~g}$ of $\mathrm{CO}_{2}$ and $0.119 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$ were collected. What is the molecular formula of dimethyl phthalate?

Keauna Shoemake

Keauna Shoemake

Numerade Educator

Problem 50

Nicotine is a poisonous, addictive compound found in tobacco. A sample of nicotine contains $6.16 \mathrm{mmol}$ of $\mathrm{C}, 8.56 \mathrm{mmol}$ $$
\text { of } \mathrm{H} \text { , and } 1.23 \mathrm{mmol} \text { of } \left.\mathrm{N}[1 \mathrm{mmol} \text { ( } 1 \text { millimole })=10^{-3} \mathrm{~mol}\right] \text { . }
$$ $$
\text { What is the empirical formula of nicotine? }
$$

Shaelyn Deal

Numerade Educator

Problem 51

Cortisol $(\mathscr{A}=362.47 \mathrm{~g} / \mathrm{mol})$ is a steroid hormone involved in protein synthesis. Medically, it has a major use in reducing inflammation from rheumatoid arthritis. Cortisol is $69.6 \% \mathrm{C}$, $8.34 \% \mathrm{H},$ and $22.1 \% \mathrm{O}$ by mass. What is its molecular formula?

Stephen Ho

Numerade Educator

Problem 52

Acetaminophen (below) is a popular nonaspirin pain reliever. What is the mass $\%$ of each element in acetaminophen?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 53

What three types of information does a balanced chemical equation provide? How?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 54

How does a balanced chemical equation apply the law of conservation of mass?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 55

In the process of balancing the equation
$$
\mathrm{A} 1+\mathrm{Cl}_{2} \longrightarrow \mathrm{A} 1 \mathrm{C} 1_{3}
$$
Student I writes: $\mathrm{A} 1+\mathrm{C} 1_{2} \longrightarrow \mathrm{A} 1 \mathrm{Cl}_{2}$
Student II writes: $\mathrm{A} 1+\mathrm{C} 1_{2}+\mathrm{C} 1 \longrightarrow \mathrm{A} 1 \mathrm{C} 1_{3}$
Student III writes: $2 \mathrm{~A} 1+3 \mathrm{Cl}_{2} \longrightarrow 2 \mathrm{~A} 1 \mathrm{Cl}_{3}$
Is the approach of Student I valid? Student II? Student III? Explain.

Shaelyn Deal

Numerade Educator

Problem 56

3.56 The scenes below represent a chemical reaction between elements A (red) and B (green): Which best represents the balanced equation for the reaction?
(a) $2 \mathrm{~A}+2 \mathrm{~B} \longrightarrow \mathrm{A}_{2}+\mathrm{B}_{2}$
(b) $\mathrm{A}_{2}+\mathrm{B}_{2} \longrightarrow 2 \mathrm{AB}$
(c) $\mathrm{B}_{2}+2 \mathrm{AB} \longrightarrow 2 \mathrm{~B}_{2}+\mathrm{A}_{2}$
(d) $4 \mathrm{~A}_{2}+4 \mathrm{~B}_{2} \longrightarrow 8 \mathrm{AB}$

Shaelyn Deal

Numerade Educator

Problem 57

Write a balanced equation for the following gas phase reaction (carbon is black, hydrogen is light blue, and fluorine is green ):

Shaelyn Deal

Numerade Educator

Problem 58

3.58 Write balanced equations for each of the following by inserting the correct coefficients in the blanks:
(a) $-\mathrm{Cu}(s)+\underline{\mathrm{S}}_{8}(s) \longrightarrow-\mathrm{Cu}_{2} \mathrm{~S}(s)$
(b) $-\mathrm{P}_{4} \mathrm{O}_{10}(s)+\underline{\mathrm{H}}_{2} \mathrm{O}(l) \longrightarrow-\mathrm{H}_{3} \mathrm{PO}_{4}(l)$
(c) $-\mathrm{B}_{2} \mathrm{O}_{3}(s)+-\mathrm{NaOH}(a q) \longrightarrow-\mathrm{Na}_{3} \mathrm{BO}_{3}(a q)+-\mathrm{H}_{2} \mathrm{O}(l)$
(d) $-\mathrm{CH}_{3} \mathrm{NH}_{2}(g)+\underline{\mathrm{O}_{2}}(g) \longrightarrow$ $-\mathrm{CO}_{2}(g)+-\mathrm{H}_{2} \mathrm{O}(g)+-\mathrm{N}_{2}(g)$

Shaelyn Deal

Numerade Educator

Problem 59

Write balanced equations for each of the following by inserting the correct coefficients in the blanks:
(a) $-\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\longrightarrow \mathrm{KOH}(a q) \longrightarrow$
(b)
(c) $-\mathrm{CaSiO}_{3}(s)+\underline{\mathrm{HF}}(g) \longrightarrow$
$$
\mathrm{SiF}_{4}(g)+\underline{\mathrm{CaF}_{2}(s)+}-\mathrm{H}_{2} \mathrm{O}(l)
$$
(d)

Shaelyn Deal

Numerade Educator

Problem 60

Write balanced equations for each of the following by inserting the correct coefficients in the blanks:
(a) $\mathrm{SO}_{2}(g)+\underline{\mathrm{O}_{2}}(g) \longrightarrow \underline{\mathrm{SO}_{3}(g)}$
(b) $-\mathrm{Sc}_{2} \mathrm{O}_{3}(s)+-\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow-\mathrm{Sc}(\mathrm{OH})_{3}(s)$
(c) $-\mathrm{H}_{3} \mathrm{PO}_{4}(a q)+\underline{\mathrm{NaOH}}(a q) \longrightarrow$
(d) $-\mathrm{C}_{6} \mathrm{H}_{10} \mathrm{O}_{5}(s)+\underline{\mathrm{O}}_{2}(g) \longrightarrow \underline{\mathrm{CO}}_{2}(\mathrm{~g})+\underline{\mathrm{H}}_{2} \mathrm{O}(g)$

Shaelyn Deal

Numerade Educator

Problem 61

Write balanced equations for each of the following by inserting the correct coefficients in the blanks:
(a) $-\mathrm{As}_{4} \mathrm{~S}_{6}(s)+\underline{\mathrm{O}_{2}}(g) \longrightarrow-\mathrm{As}_{4} \mathrm{O}_{6}(s)+-\mathrm{SO}_{2}(g)$
(b) $-\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}(s)+\mathrm{SiO}_{2}(s)+\underline{\mathrm{C}}(s) \longrightarrow$
$$
\mathrm{P}_{4}(g)+\underline{\mathrm{CaSiO}}_{3}(l)+\underline{\mathrm{CO}(g)}
$$
(c) $-\mathrm{Fe}(s)+-\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow-\mathrm{Fe}_{3} \mathrm{O}_{4}(s)+-\mathrm{H}_{2}(g)$
(d) $-\mathrm{S}_{2} \mathrm{Cl}_{2}(l)+-\mathrm{NH}_{3}(g) \longrightarrow$
$$
\mathrm{S}_{4} \mathrm{~N}_{4}(s)+\underline{\mathrm{S}}_{8}(s)+\underline{\mathrm{NH}_{4} \mathrm{Cl}(s)}
$$

Stephen Ho

Numerade Educator

Problem 62

Convert the following into balanced equations:
(a) When gallium metal is heated in oxygen gas, it melts and forms solid gallium(III) oxide.
(b) Liquid hexane burns in oxygen gas to form carbon dioxide gas and water vapor.
(c) When solutions of calcium chloride and sodium phosphate are mixed, solid calcium phosphate forms and sodium chloride remains in solution.

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 63

Convert the following into balanced equations:
(a) When lead(II) nitrate solution is added to potassium iodide solution, solid lead(II) iodide forms and potassium nitrate solution remains.
(b) Liquid disilicon hexachloride reacts with water to form solid silicon dioxide, hydrogen chloride gas, and hydrogen gas.
(c) When nitrogen dioxide is bubbled into water, a solution of nitric acid forms and gaseous nitrogen monoxide is released.

Shaelyn Deal

Numerade Educator

Problem 64

Loss of atmospheric ozone has led to an ozone "hole" over Antarctica. The loss occurs in part through three consecutive steps:
(1) Chlorine atoms react with ozone $\left(\mathrm{O}_{3}\right)$ to form chlorine monoxide and molecular oxygen.
(2) Chlorine monoxide forms $\mathrm{ClOOCl}$.
(3) $\mathrm{ClOOCl}$ absorbs sunlight and breaks into chlorine atoms and molecular oxygen.
(a) Write a balanced equation for each step.
(b) Write an overall balanced equation for the sequence.

Keauna Shoemake

Keauna Shoemake

Numerade Educator

Problem 65

What does the term stoichiometrically equivalent molar ratio mean, and how is it applied in solving problems?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 66

Percent yields are generally calculated from masses. Would the result be the same if amounts (mol) were used instead? Why?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 67

Reactants $\mathrm{A}$ and $\mathrm{B}$ form product $\mathrm{C}$. Draw a road map and write a plan to find the mass $(\mathrm{g})$ of $\mathrm{C}$ when $25 \mathrm{~g}$ of $\mathrm{A}$ reacts with excess $\mathrm{B}$.

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 68

Reactants $\mathrm{D}$ and $\mathrm{E}$ form product $\mathrm{F}$. Draw a road map and write a plan to find the mass (g) of $\mathrm{F}$ when $27 \mathrm{~g}$ of $\mathrm{D}$ reacts with $31 \mathrm{~g}$ of $\mathrm{E}$

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 69

Chlorine gas can be made in the laboratory by the reaction of hydrochloric acid and manganese(IV) oxide:
$$
4 \mathrm{HCl}(a q)+\mathrm{MnO}_{2}(s) \longrightarrow \mathrm{MnCl}_{2}(a q)+2 \mathrm{H}_{2} \mathrm{O}(g)+\mathrm{Cl}_{2}(g)
$$
When 1.82 mol of $\mathrm{HCl}$ reacts with excess $\mathrm{MnO}_{2}$, how many
(a) moles of $\mathrm{Cl}_{2}$ and (b) grams of $\mathrm{Cl}_{2}$ form?

Stephen Ho

Numerade Educator

Problem 70

Bismuth oxide reacts with carbon to form bismuth metal:
$$
\mathrm{Bi}_{2} \mathrm{O}_{3}(s)+3 \mathrm{C}(s) \longrightarrow 2 \mathrm{Bi}(s)+3 \mathrm{CO}(g)
$$
When $0.607 \mathrm{~mol}$ of $\mathrm{Bi}_{2} \mathrm{O}_{3}$ reacts with excess carbon, how many
(a) moles of Bi and (b) grams of CO form?

Shaelyn Deal

Numerade Educator

Problem 71

Potassium nitrate decomposes on heating, producing potassium oxide and gaseous nitrogen and oxygen:
$$
4 \mathrm{KNO}_{3}(s) \longrightarrow 2 \mathrm{~K}_{2} \mathrm{O}(s)+2 \mathrm{~N}_{2}(g)+5 \mathrm{O}_{2}(g)
$$
To produce $56.6 \mathrm{~kg}$ of oxygen, how many (a) moles of $\mathrm{KNO}_{3}$ and
(b) grams of $\mathrm{KNO}_{3}$ must be heated?

Stephen Ho

Numerade Educator

Problem 72

Chromium(III) oxide reacts with hydrogen sulfide $\left(\mathrm{H}_{2} \mathrm{~S}\right)$ gas to form chromium(III) sulfide and water:
$$
\mathrm{Cr}_{2} \mathrm{O}_{3}(s)+3 \mathrm{H}_{2} \mathrm{~S}(g) \longrightarrow \mathrm{Cr}_{2} \mathrm{~S}_{3}(s)+3 \mathrm{H}_{2} \mathrm{O}(l)
$$
To produce $421 \mathrm{~g}$ of $\mathrm{Cr}_{2} \mathrm{~S}_{3},$ how many (a) moles of $\mathrm{Cr}_{2} \mathrm{O}_{3}$ and
(b) grams of $\mathrm{Cr}_{2} \mathrm{O}_{3}$ are required?

Shaelyn Deal

Numerade Educator

Problem 73

Calculate the mass $(\mathrm{g})$ of each product formed when $43.82 \mathrm{~g}$ of diborane $\left(\mathrm{B}_{2} \mathrm{H}_{6}\right)$ reacts with excess water:
$$
\mathrm{B}_{2} \mathrm{H}_{6}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{H}_{3} \mathrm{BO}_{3}(s)+\mathrm{H}_{2}(g) \quad[\text { unbalanced }]
$$

Stephen Ho

Numerade Educator

Problem 74

Calculate the mass (g) of each product formed when $174 \mathrm{~g}$ of silver sulfide reacts with excess hydrochloric acid:
$$
\mathrm{Ag}_{2} \mathrm{~S}(s)+\mathrm{HCl}(a q) \longrightarrow \mathrm{AgCl}(s)+\mathrm{H}_{2} \mathrm{~S}(g)[\text { unbalanced }]
$$

Stephen Ho

Numerade Educator

Problem 75

Elemental phosphorus occurs as tetratomic molecules, $\mathrm{P}_{4}$. What mass (g) of chlorine gas is needed to react completely with $455 \mathrm{~g}$ of phosphorus to form phosphorus pentachloride?

Stephen Ho

Numerade Educator

Problem 76

Elemental sulfur occurs as octatomic molecules, $\mathrm{S}_{8} .$ What mass $(\mathrm{g})$ of fluorine gas is needed to react completely with $17.8 \mathrm{~g}$ of sulfur to form sulfur hexafluoride?

Stephen Ho

Numerade Educator

Problem 77

Solid iodine trichloride is prepared in two steps: first, a reaction between solid iodine and gaseous chlorine to form solid iodine monochloride; second, treatment of the solid with more chlorine gas.
(a) Write a balanced equation for each step.
(b) Write a balanced equation for the overall reaction.
(c) How many grams of iodine are needed to prepare $2.45 \mathrm{~kg}$ of final product?

Shaelyn Deal

Numerade Educator

Problem 78

Lead can be prepared from galena [lead(II) sulfide] by first roasting the galena in oxygen gas to form lead(II) oxide and sulfur dioxide. Heating the metal oxide with more galena forms the molten metal and more sulfur dioxide.
(a) Write a balanced equation for each step.
(b) Write an overall balanced equation for the process.
(c) How many metric tons of sulfur dioxide form for every metric ton of lead obtained?

LP

Laura Pickett

Numerade Educator

Problem 79

The scene below represents a mixture of $\mathrm{A}_{2}$ (blue) and $\mathrm{B}_{2}$ (green) before they react to form $\mathrm{AB}_{3}$.
(a) What is the limiting reactant?
(b) How many molecules of product can form?

Shaelyn Deal

Numerade Educator

Problem 80

The following scene shows a mixture of nitrogen (dark blue) and hydrogen (light blue) before they react to produce ammonia, $\mathrm{NH}_{3}$. What is the limiting reactant? Draw a scene that shows the number of reactant and product molecules present after reaction.

Shaelyn Deal

Numerade Educator

Problem 81

Methanol, $\mathrm{CH}_{3} \mathrm{OH}$, is produced from the reaction of carbon monoxide and hydrogen:
$$
\mathrm{CO}(g)+2 \mathrm{H}_{2}(g) \longrightarrow \mathrm{CH}_{3} \mathrm{OH}(l)
$$
How many moles of methanol can be produced when $4.5 \mathrm{~mol}$ of CO reacts with 7.2 mol of $\mathrm{H}_{2} ?$

Shaelyn Deal

Numerade Educator

Problem 82

In the following reaction, $2.35 \mathrm{~mol}$ of $\mathrm{NH}_{3}$ reacts with $2.75 \mathrm{~mol}$ of $\mathrm{O}_{2}$; how many moles of water form?
$$
4 \mathrm{NH}_{3}(g)+5 \mathrm{O}_{2}(g) \longrightarrow 4 \mathrm{NO}(g)+6 \mathrm{H}_{2} \mathrm{O}(l)
$$

Shaelyn Deal

Numerade Educator

Problem 83

Many metals react with oxygen gas to form the metal oxide. For example, calcium reacts as follows:
$$
2 \mathrm{Ca}(s)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CaO}(s)
$$
You wish to calculate the mass (g) of calcium oxide that can be prepared from $4.20 \mathrm{~g}$ of $\mathrm{Ca}$ and $2.80 \mathrm{~g}$ of $\mathrm{O}_{2}$.
(a) What amount (mol) of CaO can be produced from the given mass of Ca?
(b) What amount (mol) of CaO can be produced from the given mass of $\mathrm{O}_{2} ?$
(c) Which is the limiting reactant?
(d) How many grams of CaO can be produced?

Stephen Ho

Numerade Educator

Problem 84

Metal hydrides react with water to form hydrogen gas and the metal hydroxide. For example,
$$
\operatorname{SrH}_{2}(s)+2 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \operatorname{Sr}(\mathrm{OH})_{2}(s)+2 \mathrm{H}_{2}(g)
$$
You wish to calculate the mass (g) of hydrogen gas that can be prepared from $5.70 \mathrm{~g}$ of $\mathrm{SrH}_{2}$ and $4.75 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$
(a) What amount (mol) of $\mathrm{H}_{2}$ can be produced from the given mass of $\mathrm{SrH}_{2} ?$
(b) What amount (mol) of $\mathrm{H}_{2}$ can be produced from the given mass of $\mathrm{H}_{2} \mathrm{O} ?$
(c) Which is the limiting reactant?
(d) How many grams of $\mathrm{H}_{2}$ can be produced?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 85

Calculate the maximum numbers of moles and grams of iodic acid (HIO $_{3}$ ) that can form when 635 g of iodine trichloride reacts with $118.5 \mathrm{~g}$ of water:
$$
\mathrm{ICl}_{3}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{ICl}+\mathrm{HIO}_{3}+\mathrm{HCl} \text { [unbalanced] }
$$
How many grams of the remain?

Shaelyn Deal

Numerade Educator

Problem 86

Calculate the maximum numbers of moles and grams of $\mathrm{H}_{2} \mathrm{~S}$ that can form when $158 \mathrm{~g}$ of aluminum sulfide reacts with $131 \mathrm{~g}$ of water:
$$
\mathrm{Al}_{2} \mathrm{~S}_{3}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{Al}(\mathrm{OH})_{3}+\mathrm{H}_{2} \mathrm{~S}[\text { unbalanced }]
$$
How many grams of the excess reactant remain?

Shaelyn Deal

Numerade Educator

Problem 87

When $0.100 \mathrm{~mol}$ of carbon is burned in a closed vessel with $8.00 \mathrm{~g}$ of oxygen, how many grams of carbon dioxide can form? Which reactant is in excess, and how many grams of it remain after the reaction?

Stephen Ho

Numerade Educator

Problem 88

A mixture of $0.0375 \mathrm{~g}$ of hydrogen and $0.0185 \mathrm{~mol}$ of oxygen in a closed container is sparked to initiate a reaction. How many grams of water can form? Which reactant is in excess, and how many grams of it remain after the reaction?

Cheryl Glor

Numerade Educator

Problem 89

Aluminum nitrite and ammonium chloride react to form aluminum chloride, nitrogen, and water. How many grams of each substance are present after $72.5 \mathrm{~g}$ of aluminum nitrite and $58.6 \mathrm{~g}$ of ammonium chloride react completely?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 90

Calcium nitrate and ammonium fluoride react to form calcium fluoride, dinitrogen monoxide, and water vapor. How many grams of each substance are present after $16.8 \mathrm{~g}$ of calcium nitrate and $17.50 \mathrm{~g}$ of ammonium fluoride react completely?

Stephen Ho

Numerade Educator

Problem 90

Calcium nitrate and ammonium fluoride react to form calcium fluoride, dinitrogen monoxide, and water vapor. How many grams of each substance are present after $16.8 \mathrm{~g}$ of calcium nitrate and $17.50 \mathrm{~g}$ of ammonium fluoride react completely?

Stephen Ho

Numerade Educator

Problem 91

Two successive reactions, $\mathrm{A} \longrightarrow \mathrm{B}$ and $\mathrm{B} \longrightarrow \mathrm{C},$ have yields of $73 \%$ and $68 \%,$ respectively. What is the overall percent yield for conversion of A to C?

Stephen Ho

Numerade Educator

Problem 92

Two successive reactions, $\mathrm{D} \longrightarrow \mathrm{E}$ and $\mathrm{E} \longrightarrow \mathrm{F},$ have yields of $48 \%$ and $73 \%$, respectively. What is the overall percent yield for conversion of $\mathrm{D}$ to $\mathrm{F} ?$

Shaelyn Deal

Numerade Educator

Problem 93

What is the percent yield of a reaction in which $45.5 \mathrm{~g}$ of tungsten(VI) oxide (WO $_{3}$ ) reacts with excess hydrogen gas to produce metallic tungsten and $9.60 \mathrm{~mL}$ of water $(d=1.00 \mathrm{~g} / \mathrm{mL}) ?$

Stephen Ho

Numerade Educator

Problem 94

What is the percent yield of a reaction in which $200 . \mathrm{g}$ of phosphorus trichloride reacts with excess water to form $128 \mathrm{~g}$ of $\mathrm{HCl}$ and aqueous phosphorous acid $\left(\mathrm{H}_{3} \mathrm{PO}_{3}\right) ?$

Cheryl Glor

Numerade Educator

Problem 95

When $20.5 \mathrm{~g}$ of methane and $45.0 \mathrm{~g}$ of chlorine gas undergo a reaction that has a $75.0 \%$ yield, what mass $(\mathrm{g})$ of chloromethane (CH $_{3}$ Cl) forms? Hydrogen chloride also forms.

Stephen Ho

Numerade Educator

Problem 96

When $56.6 \mathrm{~g}$ of calcium and $30.5 \mathrm{~g}$ of nitrogen gas undergo a reaction that has a $93.0 \%$ yield, what mass (g) of calcium nitride forms?

Cheryl Glor

Numerade Educator

Problem 97

Cyanogen, $(\mathrm{CN})_{2},$ has been observed in the atmosphere of Titan, Saturn's largest moon, and in the gases of interstellar nebulas. On Earth, it is used as a welding gas and a fumigant. In its reaction with fluorine gas, carbon tetrafluoride and nitrogen trifluoride gases are produced. What mass (g) of carbon tetrafluoride forms when $60.0 \mathrm{~g}$ of each reactant is used?

Shaelyn Deal

Numerade Educator

Problem 98

Gaseous dichlorine monoxide decomposes readily to chlorine (green) and oxygen (red) gases.
(a) Which scene best depicts the product mixture after the decomposition?
(b) Write the balanced equation for the decomposition.
(c) If each oxygen atom represents 0.050 mol, how many molecules of dichlorine monoxide were present before the decomposition?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 99

An intermediate step in the production of nitric acid involves the reaction of ammonia with oxygen gas to form nitrogen monoxide and water. How many grams of nitrogen monoxide can form in the reaction of $485 \mathrm{~g}$ of ammonia with $792 \mathrm{~g}$ of oxygen?

Stephen Ho

Numerade Educator

Problem 100

Butane gas is compressed and used as a liquid fuel in disposable cigarette lighters and lightweight camping stoves. Suppose a lighter contains $5.50 \mathrm{~mL}$ of butane $(d=0.579 \mathrm{~g} / \mathrm{mL})$
(a) How many grams of oxygen are needed to burn the butane completely?
(b) How many moles of $\mathrm{H}_{2} \mathrm{O}$ form when all the butane burns?
(c) How many total molecules of gas form when the butane burns completely?

Shaelyn Deal

Numerade Educator

Problem 101

Sodium borohydride $\left(\mathrm{NaBH}_{4}\right)$ is used industrially in many organic syntheses. One way to prepare it is by reacting sodium hydride with gaseous diborane $\left(\mathrm{B}_{2} \mathrm{H}_{6}\right)$. Assuming an $88.5 \%$ yield, how many grams of $\mathrm{NaBH}_{4}$ can be prepared by reacting $7.98 \mathrm{~g}$ of sodium hydride and $8.16 \mathrm{~g}$ of diborane?

Shaelyn Deal

Numerade Educator

Problem 102

The mole is defined in terms of the carbon-12 atom. Use the definition to find (a) the mass in grams equal to 1 atomic mass unit; (b) the ratio of the gram to the atomic mass unit.

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 103

The first sulfur-nitrogen compound was prepared in 1835 and has been used to synthesize many others. In the early $1980 \mathrm{~s}$ researchers made another such compound that conducts electricity like a metal. Mass spectrometry of the compound shows a molar mass of $184.27 \mathrm{~g} / \mathrm{mol}$, and analysis shows it to contain 2.288 g of $\mathrm{S}$ for every $1.000 \mathrm{~g}$ of $\mathrm{N}$. What is its molecular formula?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 104

Hydroxyapatite, $\mathrm{Ca}_{5}\left(\mathrm{PO}_{4}\right)_{3}(\mathrm{OH}),$ is the main mineral component of dental enamel, dentin, and bone. Coating the compound on metallic implants (such as titanium alloys and stainless steels) helps the body accept the implant. When placed in bone voids, the powder encourages natural bone to grow into the void. Hydroxyapatite is prepared by adding aqueous phosphoric acid to a dilute slurry of calcium hydroxide. (a) Write a balanced equation for this preparation. (b) What mass (g) of hydroxyapatite could form from $100 . \mathrm{g}$ of $85 \%$ phosphoric acid and $100 . \mathrm{g}$ of calcium hydroxide?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 105

Narceine is a narcotic in opium that crystallizes from solution as a hydrate that contains 10.8 mass $\%$ water and has a molar mass of $499.52 \mathrm{~g} / \mathrm{mol} .$ Determine $x$ in narceine $x \mathrm{H}_{2} \mathrm{O}$.

Stephen Ho

Numerade Educator

Problem 106

Hydrogen-containing fuels have a "fuel value" based on their mass $\%$ H. Rank the following compounds from highest fuel value to lowest: ethane, propane, benzene, ethanol, cetyl palmitate (whale oil, $\mathrm{C}_{32} \mathrm{H}_{64} \mathrm{O}_{2}$ ).

Shaelyn Deal

Numerade Educator

Problem 107

Serotonin $(\mathscr{M}=176 \mathrm{~g} / \mathrm{mol})$ transmits nerve impulses between neurons. It contains $68.2 \%$ C, $6.86 \%$ H, $15.9 \%$ N, and $9.08 \%$ O by mass. What is its molecular formula?

Stephen Ho

Numerade Educator

Problem 108

In $1961,$ scientists agreed that the atomic mass unit (amu) would be defined as $\frac{1}{12}$ the mass of an atom of ${ }^{12} \mathrm{C}$. Before then, it was defined as $\frac{1}{16}$ the average mass of an atom of naturally occur-
ring oxygen (a mixture of ${ }^{16} \mathrm{O},{ }^{17} \mathrm{O},$ and $\left.{ }^{18} \mathrm{O}\right) .$ The current atomic mass of oxygen is 15.9994 amu. (a) Did Avogadro's number change after the definition of an amu changed and, if so, in what direction? (b) Did the definition of the mole change? (c) Did the mass of a mole of a substance change? (d) Before $1961,$ was Avogadro's number $6.02 \times 10^{23}$ (to three significant figures), as it is today?

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 109

Convert the following descriptions into balanced equations:
(a) In a gaseous reaction, hydrogen sulfide burns in oxygen to form sulfur dioxide and water vapor.
(b) When crystalline potassium chlorate is heated to just above its melting point, it reacts to form two different crystalline compounds, potassium chloride and potassium perchlorate.
(c) When hydrogen gas is passed over powdered iron(III) oxide, iron metal and water vapor form.
(d) The combustion of gaseous ethane in air forms carbon dioxide and water vapor.
(e) Iron(II) chloride is converted to iron(III) fluoride by treatment with chlorine trifluoride gas. Chlorine gas is also formed.

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 110

Isobutylene is a hydrocarbon used in the manufacture of synthetic rubber. When $0.847 \mathrm{~g}$ of isobutylene was subjected to combustion analysis, the gain in mass of the $\mathrm{CO}_{2}$ absorber was $2.657 \mathrm{~g}$ and that of the $\mathrm{H}_{2} \mathrm{O}$ absorber was $1.089 \mathrm{~g} .$ What is the empirical formula of isobutylene?

Stephen Ho

Numerade Educator

Problem 111

The multistep smelting of ferric oxide to form elemental iron occurs at high temperatures in a blast furnace. In the first step, ferric oxide reacts with carbon monoxide to form $\mathrm{Fe}_{3} \mathrm{O}_{4}$. This substance reacts with more carbon monoxide to form iron(II) oxide, which reacts with still more carbon monoxide to form molten iron. Carbon dioxide is also produced in each step. (a) Write an overall balanced equation for the iron-smelting process. (b) How many grams of carbon monoxide are required to form 45.0 metric tons of iron from ferric oxide?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 112

One of the compounds used to increase the octane rating of gasoline is toluene (ball-and-stick model is shown). Suppose $20.0 \mathrm{~mL}$ of toluene $(d=0.867 \mathrm{~g} / \mathrm{mL})$ is consumed when a sample of gasoline burns in air.
(a) How many grams of oxygen are needed for complete combustion of the toluene? (b) How many total moles of gaseous products form? (c) How many molecules of water vapor form?

Shaelyn Deal

Numerade Educator

Problem 113

During studies of the reaction in Sample Problem 3.17 ,
$$
2 \mathrm{~N}_{2} \mathrm{H}_{4}(l)+\mathrm{N}_{2} \mathrm{O}_{4}(l) \longrightarrow 3 \mathrm{~N}_{2}(g)+4 \mathrm{H}_{2} \mathrm{O}(g)
$$
a chemical engineer measured a less-than-expected yield of $\mathrm{N}_{2}$ and discovered that the following side reaction occurs:
$$
\mathrm{N}_{2} \mathrm{H}_{4}(l)+2 \mathrm{~N}_{2} \mathrm{O}_{4}(l) \longrightarrow 6 \mathrm{NO}(g)+2 \mathrm{H}_{2} \mathrm{O}(g)
$$
In one experiment, $10.0 \mathrm{~g}$ of NO formed when $100.0 \mathrm{~g}$ of each reactant was used. What is the highest percent yield of $\mathrm{N}_{2}$ that can be expected?

Shaelyn Deal

Numerade Educator

Problem 114

A 0.652 -g sample of a pure strontium halide reacts with excess sulfuric acid. The solid strontium sulfate formed is separated, dried, and found to weigh $0.755 \mathrm{~g}$. What is the formula of the original halide?

Stephen Ho

Numerade Educator

Problem 115

The following scenes represent a chemical reaction between $\mathrm{AB}_{2}$ and $\mathrm{B}_{2}$
(a) Write a balanced equation for the reaction. (b) What is the limiting reactant? (c) How many moles of product can be made from $3.0 \mathrm{~mol}$ of $\mathrm{B}_{2}$ and $5.0 \mathrm{~mol}$ of $\mathrm{AB}_{2} ?$ (d) How many moles of excess reactant remain after the reaction in part (c)?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 116

Which of the following models represent compounds having the same empirical formula? What is the empirical formula mass of this common formula?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 117

The zirconium oxalate $\mathrm{K}_{2} \mathrm{Zr}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{3}\left(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\right) \cdot \mathrm{H}_{2} \mathrm{O}$ was
synthesized by mixing $1.68 \mathrm{~g}$ of $\mathrm{ZrOCl}_{2} \cdot 8 \mathrm{H}_{2} \mathrm{O}$ with $5.20 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4} \cdot 2 \mathrm{H}_{2} \mathrm{O}$ and an excess of aqueous $\mathrm{KOH}$. After $2 \mathrm{months}$
$1.25 \mathrm{~g}$ of crystalline product was obtained, along with aqueous $\mathrm{KCl}$ and water. Calculate the percent yield.

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 118

Seawater is approximately $4.0 \%$ by mass dissolved ions, $85 \%$ of which are from $\mathrm{NaCl}$. (a) Find the mass $\%$ of $\mathrm{NaCl}$ in seawater.
(b) Find the mass \% of $\mathrm{Na}^{+}$ ions and of $\mathrm{Cl}^{-}$ ions in seawater.

Shaelyn Deal

Numerade Educator

Problem 119

Is each of the following statements true or false? Correct any that are false.
(a) A mole of one substance has the same number of atoms as a mole of any other substance.
(b) The theoretical yield for a reaction is based on the balanced chemical equation.
(c) A limiting-reactant problem is being stated when the available quantity of one of the reactants is given in moles.
(d) The empirical and molecular formulas of a compound are always different.

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 120

In each pair, choose the larger of the indicated quantities or state that the samples are equal:
(a) Entities: $0.4 \mathrm{~mol}$ of $\mathrm{O}_{3}$ molecules or $0.4 \mathrm{~mol}$ of $\mathrm{O}$ atoms
(b) Grams: $0.4 \mathrm{~mol}$ of $\mathrm{O}_{3}$ molecules or $0.4 \mathrm{~mol}$ of $\mathrm{O}$ atoms
(c) Moles: $4.0 \mathrm{~g}$ of $\mathrm{N}_{2} \mathrm{O}_{4}$ or $3.3 \mathrm{~g}$ of $\mathrm{SO}_{2}$
(d) Grams: $0.6 \mathrm{~mol}$ of $\mathrm{C}_{2} \mathrm{H}_{4}$ or $0.6 \mathrm{~mol}$ of $\mathrm{F}_{2}$
(e) Total ions: $2.3 \mathrm{~mol}$ of sodium chlorate or $2.2 \mathrm{~mol}$ of magnesium chloride
(f) Molecules: $1.0 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}$ or $1.0 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O}_{2}$
(g) Grams: $6.02 \times 10^{23}$ atoms of ${ }^{235} \mathrm{U}$ or $6.02 \times 10^{23}$ atoms of ${ }^{238} \mathrm{U}$

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 121

For the reaction between solid tetraphosphorus trisulfide and oxygen gas to form solid tetraphosphorus decoxide and sulfur dioxide gas, write a balanced equation. Show the equation (see Table 3.4 ) in terms of (a) molecules, (b) moles, and
(c) grams.

Shaelyn Deal

Numerade Educator

Problem 122

Hydrogen gas is considered a clean fuel because it produces only water vapor when it burns. If the reaction has a $98.8 \%$ yield, what mass (g) of hydrogen forms $105 \mathrm{~kg}$ of water?

Stephen Ho

Numerade Educator

Problem 123

Solar winds composed of free protons, electrons, and $\alpha$ particles bombard Earth constantly, knocking gas molecules out of the atmosphere. In this way, Earth loses about $3.0 \mathrm{~kg}$ of matter per second. It is estimated the atmosphere will be gone in about 50 billion years. Use this estimate to calculate (a) the mass (kg) of Earth's atmosphere and (b) the amount (mol) of nitrogen, which makes up 75.5 mass $\%$ of the atmosphere.

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 124

Calculate each of the following quantities:
(a) Amount (mol) of 0.588 g of ammonium bromide
(b) Number of potassium ions in $88.5 \mathrm{~g}$ of potassium nitrate
(c) Mass (g) of 5.85 mol of glycerol $\left(\mathrm{C}_{3} \mathrm{H}_{8} \mathrm{O}_{3}\right)$
(d) Volume (L) of $2.85 \mathrm{~mol}$ of chloroform $\left(\mathrm{CHCl}_{3} ; d=1.48 \mathrm{~g} / \mathrm{mL}\right)$
(e) Number of sodium ions in 2.11 mol of sodium carbonate
(f) Number of atoms in $25.0 \mu \mathrm{g}$ of cadmium
(g) Number of atoms in 0.0015 mol of fluorine gas

Shaelyn Deal

Numerade Educator

Problem 125

Elements $\mathrm{X}$ ( green ) and $\mathrm{Y}$ (purple) react according to the following equation: $\mathrm{X}_{2}+3 \mathrm{Y}_{2} \longrightarrow 2 \mathrm{XY}_{3} .$ Which molecular scene represents the product of the reaction?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 126

Hydrocarbon mixtures are used as fuels. (a) How many grams of $\mathrm{CO}_{2}(g)$ are produced by the combustion of $200 . \mathrm{g}$ of a mixture that is $25.0 \% \mathrm{CH}_{4}$ and $75.0 \% \mathrm{C}_{3} \mathrm{H}_{8}$ by mass?
(b) A $252-\mathrm{g}$
gaseous mixture of $\mathrm{CH}_{4}$ and $\mathrm{C}_{3} \mathrm{H}_{8}$ burns in excess $\mathrm{O}_{2},$ and $748 \mathrm{~g}$ of $\mathrm{CO}_{2}$ gas is collected. What is the mass $\%$ of $\mathrm{CH}_{4}$ in the mixture?

Stephen Ho

Numerade Educator

Problem 127

Nitrogen (N), phosphorus (P), and potassium (K) are the main nutrients in plant fertilizers. By industry convention, the numbers on a label refer to the mass percents of $\mathrm{N}, \mathrm{P}_{2} \mathrm{O}_{5},$ and $\mathrm{K}_{2} \mathrm{O},$ in that order. Calculate the N/P/K ratio of a $30 / 10 / 10$ fertilizer in terms of moles of each element, and express it as $x / y / 1.0$.

Shaelyn Deal

Numerade Educator

Problem 128

What mass percents of ammonium sulfate, ammonium hydrogen phosphate, and potassium chloride would you use to prepare $10 / 10 / 10$ plant fertilizer (see Problem 3.127 )?

Shaelyn Deal

Numerade Educator

Problem 129

Ferrocene, synthesized in $1951,$ was the first organic iron compound with $\mathrm{Fe}-\mathrm{C}$ bonds. An understanding of the structure of ferrocene gave rise to new ideas about chemical bonding and led to the preparation of many useful compounds. In the combustion analysis of ferrocene, which contains only $\mathrm{Fe}, \mathrm{C},$ and $\mathrm{H}, \mathrm{a} 0.9437-\mathrm{g}$ sample produced $2.233 \mathrm{~g}$ of $\mathrm{CO}_{2}$ and $0.457 \mathrm{~g}$ of $\mathrm{H}_{2} \mathrm{O} .$ What is the empirical formula of ferrocene?

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 130

When carbon-containing compounds are burned in a limited amount of air, some $\mathrm{CO}(g)$ as well as $\mathrm{CO}_{2}(g)$ are produced. A gaseous product mixture is 35.0 mass $\%$ CO and 65.0 mass $\%$ CO $_{2}$. What is the mass $\%$ of $\mathrm{C}$ in the mixture?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 131

Write a balanced equation for the reaction depicted below: If each reactant molecule represents $1.25 \times 10^{-2} \mathrm{~mol}$ and the reaction yield is $87 \%$, how many grams of Si-containing product form?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 132

Citric acid (below) is concentrated in citrus fruits and plays a central metabolic role in nearly every animal and plant cell.
(a) What are the molar mass and formula of citric acid? (b) How many moles of citric acid are in 1.50 qt of lemon juice $(d=1.09 \mathrm{~g} / \mathrm{mL})$ that is $6.82 \%$ citric acid by mass?

Shaelyn Deal

Numerade Educator

Problem 133

Various nitrogen oxides, as well as sulfur oxides, contribute to acidic rainfall through complex reaction sequences. Nitrogen and oxygen combine during the high-temperature combustion of fuels in air to form nitrogen monoxide gas, which reacts with more oxygen to form nitrogen dioxide gas. In contact with water vapor, nitrogen dioxide forms aqueous nitric acid and more nitrogen monoxide. (a) Write balanced equations for these reactions. (b) Use the equations to write one overall balanced equation that does not include nitrogen monoxide and nitrogen dioxide. (c) How many metric tons (t) of nitric acid form when $1350 \mathrm{t}$ of atmospheric nitrogen is consumed $(1 \mathrm{t}=1000 \mathrm{~kg}) ?$

Shaelyn Deal

Numerade Educator

Problem 134

Nitrogen monoxide reacts with elemental oxygen to form nitrogen dioxide. The first scene below represents an initial mixture of reactants. If the reaction has a $66 \%$ yield, which of the lower scenes (A, B, or C) best represents the final product mixture?

Shaelyn Deal

Numerade Educator

Problem 135

Fluorine is so reactive that it forms compounds with several of the noble gases.
(a) When $0.327 \mathrm{~g}$ of platinum is heated in fluorine, $0.519 \mathrm{~g}$ of a dark red, volatile solid forms. What is its empirical formula?
(b) When $0.265 \mathrm{~g}$ of this red solid reacts with excess xenon gas, $0.378 \mathrm{~g}$ of an orange-yellow solid forms. What is the empirical formula of this compound, the first to contain a noble gas?
(c) Fluorides of xenon can be formed by direct reaction of the elements at high pressure and temperature. Under conditions that produce only the tetra- and hexafluorides, $1.85 \times 10^{-4} \mathrm{~mol}$ of xenon reacted with $5.00 \times 10^{-4} \mathrm{~mol}$ of fluorine, and $9.00 \times 10^{-6} \mathrm{~mol}$ of xenon was found in excess. What are the mass percents of each xenon fluoride in the product mixture?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 136

Hemoglobin is $6.0 \%$ heme $\left(\mathrm{C}_{34} \mathrm{H}_{32} \mathrm{FeN}_{4} \mathrm{O}_{4}\right)$ by mass. To
remove the heme, hemoglobin is treated with acetic acid and $\mathrm{NaCl},$ which forms hemin $\left(\mathrm{C}_{34} \mathrm{H}_{32} \mathrm{~N}_{4} \mathrm{O}_{4} \mathrm{FeCl}\right) .$ A blood sample
from a crime scene contains $0.65 \mathrm{~g}$ of hemoglobin. (a) How many grams of heme are in the sample? (b) How many moles of heme?
(c) How many grams of Fe? (d) How many grams of hemin could be formed for a forensic chemist to measure?

Shaelyn Deal

Numerade Educator

Problem 137

Manganese is a key component of extremely hard steel. The element occurs naturally in many oxides. A 542.3 -g sample of a manganese oxide has an $\mathrm{Mn} / \mathrm{O}$ ratio of $1.00 / 1.42$ and consists of braunite $\left(\mathrm{Mn}_{2} \mathrm{O}_{3}\right)$ and manganosite $(\mathrm{MnO}) .$ (a) How many grams of braunite and of manganosite are in the ore? (b) What is the $\mathrm{Mn}^{3+} / \mathrm{Mn}^{2+}$ ratio in the ore?

Keauna Shoemake

Keauna Shoemake

Numerade Educator

Problem 138

The human body excretes nitrogen in the form of urea, $\mathrm{NH}_{2} \mathrm{CONH}_{2}$. The key step in its biochemical formation is the reaction of water with arginine to produce urea and ornithine:
(a) What is the mass $\%$ of nitrogen in urea, in arginine, and in ornithine? (b) How many grams of nitrogen can be excreted as urea when $135.2 \mathrm{~g}$ of ornithine is produced?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 139

Aspirin (acetylsalicylic acid, $\mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}$ ) is made by reacting salicylic acid $\left(\mathrm{C}_{7} \mathrm{H}_{6} \mathrm{O}_{3}\right)$ with acetic anhydride $\left[\left(\mathrm{CH}_{3} \mathrm{CO}\right)_{2} \mathrm{O}\right]:$
$$
\mathrm{C}_{7} \mathrm{H}_{6} \mathrm{O}_{3}(s)+\left(\mathrm{CH}_{3} \mathrm{CO}\right)_{2} \mathrm{O}(l) \longrightarrow \mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}(s)+\mathrm{CH}_{3} \mathrm{COOH}(l)
$$
In one preparation, $3.077 \mathrm{~g}$ of salicylic acid and $5.50 \mathrm{~mL}$ of acetic anhydride react to form $3.281 \mathrm{~g}$ of aspirin.
(a) Which is the limiting reactant (the density of acetic anhydride is $1.080 \mathrm{~g} / \mathrm{mL}) ?$
(b) What is the percent yield of this reaction?
(c) What is the percent atom economy of this reaction?

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 140

The rocket fuel hydrazine $\left(\mathrm{N}_{2} \mathrm{H}_{4}\right)$ is made by the three-step Raschig process, which has the following overall equation:
$$
\mathrm{NaOCl}(a q)+2 \mathrm{NH}_{3}(a q) \longrightarrow \mathrm{N}_{2} \mathrm{H}_{4}(a q)+\mathrm{NaCl}(a q)+\mathrm{H}_{2} \mathrm{O}(l)
$$
What is the percent atom economy of this process?

Katherine Mccandless

Katherine Mccandless

Numerade Educator

Problem 141

Lead(II) chromate $\left(\mathrm{PbCrO}_{4}\right)$ is used as the yellow pigment for marking traffic lanes but is banned from house paint because of the risk of lead poisoning. It is produced from chromite $\left(\mathrm{FeCr}_{2} \mathrm{O}_{4}\right),$ an ore of chromium:
$$
\begin{array}{r}
4 \mathrm{FeCr}_{2} \mathrm{O}_{4}(s)+8 \mathrm{~K}_{2} \mathrm{CO}_{3}(a q)+7 \mathrm{O}_{2}(g) \longrightarrow \\
2 \mathrm{Fe}_{2} \mathrm{O}_{3}(s)+8 \mathrm{~K}_{2} \mathrm{CrO}_{4}(a q)+8 \mathrm{CO}_{2}(g)
\end{array}
$$
Lead(II) ion then replaces the $\mathrm{K}^{+}$ ion. If a yellow paint is to have $0.511 \% \mathrm{PbCrO}_{4}$ by mass, how many grams of chromite are needed per kilogram of paint?

Nicole Smina

Numerade Educator

Problem 142

Ethanol $\left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}\right),$ the intoxicant in alcoholic beverages, is also used to make other organic compounds. In concentrated sulfuric acid, ethanol forms diethyl ether and water:
$$
2 \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(l) \longrightarrow \mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OCH}_{2} \mathrm{CH}_{3}(l)+\mathrm{H}_{2} \mathrm{O}(g)
$$
In a side reaction, some ethanol forms ethylene and water:
$$
\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{OH}(l) \longrightarrow \mathrm{CH}_{2} \mathrm{CH}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(g)
$$
(a) If $50.0 \mathrm{~g}$ of ethanol yields $35.9 \mathrm{~g}$ of diethyl ether, what is the percent yield of diethyl ether? (b) If $45.0 \%$ of the ethanol that did not produce the ether reacts by the side reaction, what mass (g) of ethylene is produced?

Stephen Ho

Numerade Educator

Problem 143

When powdered zinc is heated with sulfur, a violent reaction occurs, and zinc sulfide forms:
$$
\mathrm{Zn}(s)+\mathrm{S}_{8}(s) \longrightarrow \mathrm{ZnS}(s)[\text { unbalanced }]
$$ Some of the reactants also combine with oxygen in air to form zinc oxide and sulfur dioxide. When $83.2 \mathrm{~g}$ of Zn reacts with $52.4 \mathrm{~g}$ of $\mathrm{S}_{8}$, $104.4 \mathrm{~g}$ of $\mathrm{ZnS}$ forms.
(a) What is the percent yield of $\mathrm{ZnS}$ ?
(b) If all the remaining reactants combine with oxygen, how many grams of each of the two oxides form?

Susan Hallstrom

Susan Hallstrom

Numerade Educator

Problem 144

Cocaine $\left(\mathrm{C}_{17} \mathrm{H}_{21} \mathrm{O}_{4} \mathrm{~N}\right)$ is a natural substance found in $\operatorname{coca}$
leaves, which have been used for centuries as a local anesthetic and stimulant. Illegal cocaine arrives in the United States either as the pure compound or as the hydrochloride salt $\left(\mathrm{C}_{17} \mathrm{H}_{21} \mathrm{O}_{4} \mathrm{NHCl}\right)$. At $25^{\circ} \mathrm{C},$ the salt is very soluble in water $(2.50 \mathrm{~kg} / \mathrm{L}),$ but cocaine is much less so $(1.70 \mathrm{~g} / \mathrm{L})$
(a) What is the maximum mass (g) of the hydrochloride salt that can dissolve in $50.0 \mathrm{~mL}$ of water?
(b) If the solution from part (a) is treated with $\mathrm{NaOH}$, the salt is converted to cocaine. How much more water (L) is needed to dissolve it?

Nicole Smina

Numerade Educator

Problem 145

High-temperature superconducting oxides hold great promise in the utility, transportation, and computer industries.
(a) One superconductor is $\mathrm{La}_{2-x} \mathrm{Sr}_{x} \mathrm{CuO}_{4} .$ Calculate the molar masses of this oxide when $x=0, x=1,$ and $x=0.163$.
(b) Another common superconducting oxide is made by heating a mixture of barium carbonate, copper(II) oxide, and yttrium(III) oxide, followed by further heating in $\mathrm{O}_{2}$ :
$4 \mathrm{BaCO}_{3}(s)+6 \mathrm{CuO}(s)+\mathrm{Y}_{2} \mathrm{O}_{3}(s) \longrightarrow$
$$
\begin{array}{c}
2 \mathrm{YBa}_{2} \mathrm{Cu}_{3} \mathrm{O}_{6.5}(s)+4 \mathrm{CO}_{2}(g) \\
2 \mathrm{YBa}_{2} \mathrm{Cu}_{3} \mathrm{O}_{6.5}(s)+\frac{1}{2} \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{YBa}_{2} \mathrm{Cu}_{3} \mathrm{O}_{7}(s)
\end{array}
$$
When equal masses of the three reactants are heated, which reactant is limiting?
(c) After the product in part (b) is removed, what is the mass $\%$ of each reactant in the remaining solid mixture?

Katherine Mccandless

Katherine Mccandless

Numerade Educator