Problem 1

Sodium chlorate, $\mathrm{NaClO}_{3},$ decomposes when heated to yield sodium chloride and oxygen, a reaction used to provide oxygen for the emergency breathing masks in many airliners. Balance the equation.

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Problem 2

Balance the following equations:

(a) $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}+\mathrm{CO}_{2}$ (fermentation of sugar to yield ethyl alcohol)

(b) $\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+\mathrm{O}_{2} \quad$ (photosynthesis reaction in green plants)

(c) $\mathrm{NH}_{3}+\mathrm{Cl}_{2} \longrightarrow \mathrm{N}_{2} \mathrm{H}_{4}+\mathrm{NH}_{4} \mathrm{Cl} \quad$ (synthesis of hydrazine for rocket fuel)

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Problem 3

Write a balanced equation for the reaction of element A (red spheres) with element B (green spheres) as represented below:

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Problem 4

Calculate the formula mass or molecular mass of the following substances:

(a) $\mathrm{Fe}_{2} \mathrm{O}_{3}(\text { rust) }$

(b) $\mathrm{H}_{2} \mathrm{SO}_{4}$ (sulfuric acid)

(c) $\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{7}$ (citric acid)

(d) $\mathrm{C}_{16} \mathrm{H}_{18} \mathrm{N}_{2} \mathrm{O}_{4} \mathrm{S}$ (penicillin G)

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Problem 5

Aspirin can be represented by the adjacent ball-and-stick molecular model. Give the formula for aspirin, and calculate its molecular mass (red $=\mathrm{O},$ gray $=\mathrm{C},$ ivory $=\mathrm{H} )$. How many moles of aspirin are in a tablet weighing 500 mg? How many molecules?

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Problem 6

Aspirin is prepared by reaction of salicylic acid $\left(\mathrm{C}_{7} \mathrm{H}_{6} \mathrm{O}_{3}\right)$ with acetic anhydride $\left(\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{3}\right)$ according to the following equation:

$$\mathrm{C}_{7} \mathrm{H}_{6} \mathrm{O}_{3}+\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{3} \longrightarrow \mathrm{C}_{9} \mathrm{H}_{8} \mathrm{O}_{4}+\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}$$

(a) How many grams of acetic anhydride are needed to react with 4.50 g of salicylic acid?

(b) How many grams of aspirin will result?

(c) How many grams of acetic acid are formed as a byproduct?

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Problem 7

Ethyl alcohol is prepared industrially by the reaction of ethylene, $\mathrm{C}_{2} \mathrm{H}_{4},$ with water. What is the percent yield of the reaction if 4.6 $\mathrm{g}$ of ethylene gives 4.7 $\mathrm{g}$

of ethyl alcohol?

$$\mathrm{C}_{2} \mathrm{H}_{4}(g)+\mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}(l)$$

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Problem 8

Dichloromethane $\left(\mathrm{CH}_{2} \mathrm{Cl}_{2}\right),$ used as a solvent in the decaffeination of coffee beans, is prepared by reaction of methane (CH_) with chlorine. How many grams of dichloromethane result from reaction of 1.85 $\mathrm{kg}$ of methane if the yield is 43.1$\% ?$

$$\mathrm{CH}_{4}(g)+2 \mathrm{Cl}_{2}(g) \longrightarrow \mathrm{CH}_{2} \mathrm{Cl}_{2}(l)+2 \mathrm{HCI}(g)$$

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Problem 9

Lithium oxide is used aboard the space shuttle to remove water from the air supply. If 80.0 $\mathrm{kg}$ of water is to be removed and 65 $\mathrm{kg}$ of $\mathrm{L}_{2} \mathrm{O}$ is available, which reactant is limiting? How many kilograms of the excess reactant remain?

$$\mathrm{Li}_{2} \mathrm{O}(s)+\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow 2 \mathrm{LiOH}(s)$$

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Problem 10

After lithium hydroxide is produced aboard the space shuttle by reaction of $\mathrm{Li}_{2} \mathrm{O}$ with $\mathrm{H}_{2} \mathrm{O}$ (Problem $3.9 ),$ it is used to remove exhaled carbon dioxide from the air supply. How many grams of $\mathrm{CO}_{2}$ can 500.0 $\mathrm{g}$ of LiOH absorb?

$$\mathrm{LOH}(s)+\mathrm{CO}_{2}(g) \longrightarrow \operatorname{LiHCO}_{3}(s)$$

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Problem 11

The following diagram represents the reaction of A (red spheres) with $\mathrm{B}_{2}$ (blue spheres):

(a) Write a balanced equation for the reaction, and identify the limiting reactant.

(b) How many moles of product can be made from 1.0 mol of A and 1.0 mol of $\mathrm{B}_{2} ?$

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Problem 12

How many moles of solute are present in the following solutions?

(a) 125 $\mathrm{mL}$ of 0.20 $\mathrm{MNaHCO}_{3} \quad$ (b) 650.0 $\mathrm{mL}$ of 2.50 $\mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$

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Problem 13

How many grams of solute would you use to prepare the following solutions?

(a) 500.0 $\mathrm{mL}$ of 1.25 $\mathrm{M} \mathrm{NaOH} \quad$ (b) 1.50 $\mathrm{L}$ of 0.250 $\mathrm{M}$ glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$

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Problem 14

How many milliliters of a 0.20 $\mathrm{M}$ glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ solution are needed to provide a total of 25.0 g of glucose?

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Problem 15

The concentration of cholesterol $\left(\mathrm{C}_{22} \mathrm{H}_{46} \mathrm{O}\right)$ in normal blood is approximately 0.005 M. How many grams of cholesterol are in 750 mL of blood?

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Problem 16

What is the final concentration if 75.0 mL of a 3.50 M glucose solution is diluted to a volume of 400.0 mL?

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Problem 17

Sulfuric acid is normally purchased at a concentration of 18.0 M. How would you prepare 250.0 $\mathrm{mL}$ of 0.500 $\mathrm{M}$ aqueous $\mathrm{H}_{2} \mathrm{SO}_{4} ?$ (Remember to add the acid to water rather than water to the acid.)

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Problem 18

What volume of 0.250 $\mathrm{M} \mathrm{H}_{2} \mathrm{SO}_{4}$ is needed to react with 50.0 $\mathrm{mL}$ of 0.100 $\mathrm{MNaOH} ?$ The equation is

$$\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+2 \mathrm{NaOH}(a q) \longrightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l)$$

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Problem 19

What is the molarity of an HNO $_{3}$ solution if 68.5 $\mathrm{mL}$ is needed to react with 25.0 $\mathrm{mL}$ of 0.150 $\mathrm{M}$ KOH solution? The equation is

$$\mathrm{HNO}_{3}(a q)+\mathrm{KOH}(a q) \longrightarrow \mathrm{KNO}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$$

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Problem 20

A 25.0 mL sample of vinegar (dilute acetic actid, $\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H} )$ is titrated and found to react with 94.7 mL of 0.200 M NaOH. What is the molarity of the acetic acid

solution? The reaction is

$$\mathrm{NaOH}(a q)+\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(a q) \longrightarrow \mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{Na}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$$

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Problem 21

Assume that the buret contains $\mathrm{H}^{+}$ ions, the flask contains $\mathrm{OH}^{-}$ ions, the volumes in the buret and the flask are identical, and the concentration of the acid in the buret is 1.00 $\mathrm{M}$ . If the entire volume of the buret is required for titration of the base in the flask, what is the concentration of base? The equation is $\mathrm{H}^{+}(a q)+\mathrm{OH}^{-}(a q) \longrightarrow \mathrm{H}_{2} \mathrm{O}(l)$

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Problem 22

What is the empirical formula, and what is the percent composition of dimethylhydrazine, $\mathrm{C}_{2} \mathrm{H}_{8} \mathrm{N}_{2},$ a colorless liquid used as a rocket fuel?

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Problem 23

What is the empirical formula of the ingredient in Bufferin tablets that has the percent composition $C 14.25 \%, 056.93 \%, \mathrm{Mg} 28.83 \%$ by mass?

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Problem 24

What is the percent composition of citric acid, an organic acid, commonly found in citrus fruits, whose structure is shown in the nearby margin? (Gray $=\mathrm{C}$ red $=\mathrm{O}, \mathrm{H}=$ ivory.)

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Problem 25

Menthol, a flavoring agent obtained from peppermint oil, contains carbon, hydrogen, and oxygen. On combustion analysis, 1.00 g of menthol yields 1.161 g of $\mathrm{H}_{2} \mathrm{O}$ and 2.818 $\mathrm{g}$ of $\mathrm{CO}_{2}$ . What is the empirical formula of menthol?

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Problem 26

Ribose, a sugar present in the cells of all living organisms, has a molecular mass of 150 amu and the empirical formula $\mathrm{CH}_{2} \mathrm{O}$ . What is the molecular formula of ribose?

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Problem 27

Convert the following percent compositions into molecular formulas:

(a) Diborane: $\mathrm{H} 21.86 \%, \mathrm{B} 78.14 \% ;$ Molec. mass $=27.7 \mathrm{amu}$

(b) Trioxan: $\mathrm{C} 40.00 \%, \mathrm{H} 6.71 \%, \mathrm{O} 53.28 \% ;$ Molec. mass $=90.08 \mathrm{amu}$

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Problem 28

What do you think are the main sources of error in calculating Avogadro’s number by spreading oil on a pond?

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Problem 29

Recalculate Avogadro’s number assuming that the oil molecules are shaped like tall rectangular boxes rather than cubes, with two edges of equal length and the third edge four times the length of the other two. Assume also that the molecules stand on end in the water.

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Problem 30

Box (a) represents 1.0 mL of a solution of particles at a given concentration. Which of the boxes (b)–(d) represents 1.0 mL of the solution that results after (a) has been diluted by doubling the volume of its solvent?

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Problem 31

The reaction of A (red spheres) with B (blue spheres) is shown in the following diagram:

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Problem 32

Cytosine, a constituent of deoxyribonucleic acid (DNA) can be represented by the following molecular model. If 0.001 mol of cytosine is submitted to combustion analysis, how many moles of $\mathrm{CO}_{2}$ and how many moles of $\mathrm{H}_{2} \mathrm{O}$ would be formed? (Gray $=\mathrm{C},$ red $=\mathrm{O},$ blue $=\mathrm{N},$ ivory $=\mathrm{H.}$ )

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Problem 33

If blue spheres represent nitrogen atoms and red spheres represent oxygen atoms, which box represents reactants and which represents products for the reaction $2 \mathrm{NO}(g)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{NO}_{2}(g) ?$

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Problem 34

Fluoxetine, marketed as an antidepressant under the name Prozac, can be represented by the following ball-and-stick molecular model. Write the molecular formula for fluoxetine, and calculate its molecular mass (red $=\mathrm{O},$ gray $=\mathrm{C}$ blue $=\mathrm{N},$ yellow-green $=\mathrm{F},$ ivory $=\mathrm{H}$ )

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Problem 35

What is the percent composition of cysteine, one of the 20 amino acids commonly found in proteins? (Gray $=\mathrm{C}$ , red $=\mathrm{O},$ blue $=\mathrm{N},$ yellow $=\mathrm{S},$ ivory $=\mathrm{H.}$ )

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Problem 36

The following diagram represents the reaction of $\mathrm{A}_{2}$ (red spheres) with $\mathrm{B}_{2}$ (blue spheres):

(a) Write a balanced equation for the reaction, and identify the limiting reactant.

(b) How many moles of product can be made from 1.0 $\mathrm{mol}$ of $\mathrm{A}_{2}$ and 1.0 $\mathrm{mol}$ of $\mathrm{B}_{2} ?$

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Problem 37

A hydrocarbon of unknown formula $\mathrm{C}_{x} \mathrm{H}_{\mathrm{y}}$ was submitted to combustion analysis with the following results. What is the empirical formula of the hydrocarbon?

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Problem 38

Which of the following equations are balanced?

(a) The development reaction in silver-halide photography:

$2 \mathrm{AgBr}+2 \mathrm{NaOH}+\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{O}_{2} \longrightarrow$

$2 \mathrm{Ag}+\mathrm{H}_{2} \mathrm{O}+2 \mathrm{NaBr}+\mathrm{C}_{6} \mathrm{H}_{4} \mathrm{O}_{2}$

(b) The preparation of household bleach:

$2 \mathrm{NaOH}+\mathrm{Cl}_{2} \longrightarrow \mathrm{NaOCl}+\mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}$

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Problem 39

Which of the following equations are balanced? Balance any that need it.

(a) The thermite reaction, used in welding:

$\mathrm{Al}+\mathrm{Fe}_{2} \mathrm{O}_{3} \longrightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+\mathrm{Fe}$

(b) The photosynthesis of glucose from $\mathrm{CO}_{2}$ :

$6 \mathrm{CO}_{2}+6 \mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+6 \mathrm{O}_{2}$

(c) The separation of gold from its ore:

$\mathrm{Au}+2 \mathrm{NaCN}+\mathrm{O}_{2}+\mathrm{H}_{2} \mathrm{O} \longrightarrow_{\mathrm{NaAu}(\mathrm{CN})_{2}+3 \mathrm{NaOH}}$

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Problem 40

Balance the following equations:

(a) $\mathrm{Mg}+\mathrm{HNO}_{3} \longrightarrow \mathrm{H}_{2}+\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}$

(b) $\mathrm{CaC}_{2}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{C}_{2} \mathrm{H}_{2}$

(c) $\mathrm{S}+\mathrm{O}_{2} \longrightarrow \mathrm{SO}_{3}$

(d) $\mathrm{UO}_{2}+\mathrm{HF} \longrightarrow \mathrm{UF}_{4}+\mathrm{H}_{2} \mathrm{O}$

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Problem 41

Balance the following equations:

(a) The explosion of ammonium nitrate:

$\mathrm{NH}_{4} \mathrm{NO}_{3} \longrightarrow \mathrm{N}_{2}+\mathrm{O}_{2}+\mathrm{H}_{2} \mathrm{O}$

(b) The spoilage of wine into vinegar:

$\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}+\mathrm{O}_{2} \longrightarrow \mathrm{C}_{2} \mathrm{H}_{4} \mathrm{O}_{2}+\mathrm{H}_{2} \mathrm{O}$

(c) The burning of rocket fuel:

$\mathrm{C}_{2} \mathrm{H}_{8} \mathrm{N}_{2}+\mathrm{N}_{2} \mathrm{O}_{4} \longrightarrow \mathrm{N}_{2}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}$

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Problem 42

Balance the following equations:

(a) $\mathrm{SiCl}_{4}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{SiO}_{2}+\mathrm{HCl}$

(b) $\mathrm{P}_{4} \mathrm{O}_{10}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{H}_{3} \mathrm{PO}_{4}$

(c) $\mathrm{CaCN}_{2}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{CaCO}_{3}+\mathrm{NH}_{3}$

(d) $\mathrm{NO}_{2}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{HNO}_{3}+\mathrm{NO}$

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Problem 43

Balance the following equations:

(a) $\mathrm{VCl}_{3}+\mathrm{Na}+\mathrm{CO} \longrightarrow \mathrm{V}(\mathrm{CO})_{6}+\mathrm{NaCl}$

(b) $\mathrm{Rul}_{3}+\mathrm{CO}+\mathrm{Ag} \longrightarrow \mathrm{Ru}(\mathrm{CO})_{5}+\mathrm{Ag} 1$

(c) $\mathrm{CoS}+\mathrm{CO}+\mathrm{Cu} \longrightarrow \mathrm{Co}_{2}(\mathrm{CO})_{8}+\mathrm{Cu}_{2} \mathrm{S}$

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Problem 44

What are the molecular (formula) masses of the following substances?

(a) $\mathrm{Hg}_{2} \mathrm{Cl}_{2}$ (calomel, used at one time as a bowel purgative)

(b) $\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2}$ (butyric acid, responsible for the odor of rancid butter)

(c) $\mathrm{CF}_{2} \mathrm{Cl}_{2}$ (a chlorofluorocarbon that destroys the stratospheric ozone layer)

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Problem 45

What are the formulas of the following substances?

(a) $\mathrm{PCl} ;$ Molec. mass $=137.3 \mathrm{amu}$

(b) Nicotine, $\mathrm{C}_{10} \mathrm{H}_{14} \mathrm{N}_{3}$ , Molec. mass $=162.2$ amu

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Problem 46

What are the molecular masses of the following pharmaceuticals?

(a) $\mathrm{C}_{33} \mathrm{H}_{35} \mathrm{FN}_{2} \mathrm{O}_{5}$ (atorvastatin, lowers blood cholesterol)

(b) $\mathrm{C}_{22} \mathrm{H}_{27} \mathrm{F}_{3} \mathrm{O}_{4} \mathrm{S}$ (fluticasone, anti-inflammatory)

(c) $\mathrm{C}_{16} \mathrm{H}_{16} \mathrm{CINO}_{2} \mathrm{S}$ (clopidogrel, inhibits blood clots)

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Problem 47

What are the molecular masses of the following herbicides?

(a) $\mathrm{C}_{6} \mathrm{H}_{6} \mathrm{Cl}_{2} \mathrm{O}_{3}(2,4 \text { -dichlorophenoxyacetic acid, effective }$ on broadleaf plants)

(b) $\mathrm{C}_{15} \mathrm{H}_{22} \mathrm{ClNO}_{2}$ (metolachlor, pre-emergent herbicide)

(c) $\mathrm{C}_{8} \mathrm{H}_{6} \mathrm{C}_{2} \mathrm{O}_{3}$ (dicamba, effective on broadleaf plants)

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Problem 48

How many grams are in a mole of each of the following substances?

(a) $\mathrm{Ti}$

(b) $\mathrm{Br}_{2}$

(c) Hg

(d) $\mathrm{H}_{2} \mathrm{O}$

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Problem 49

How many moles are in a gram of each of the following substances?

(a) $\mathrm{Cr}$

(b) $\mathrm{Cl}_{2}$

(c) Au

(d) $\mathrm{NH}_{3}$

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Problem 51

How many moles of anions are in 35.6 $\mathrm{g}$ of $\mathrm{AlF}_{3} ?$

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Problem 54

Iron(II) sulfate, $\mathrm{FeSO}_{4},$ is prescribed for the treatment of anemia. How many moles of FeSO_ are present in a standard 300 $\mathrm{mg}$ tablet? How many iron(II) ions?

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Problem 55

The "lead" in lead pencils is actually almost pure carbon, and the mass of a period mark made by a lead pencil is about 0.0001 g. How many carbon atoms are in the period?

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Problem 56

An average cup of coffee contains about 125 $\mathrm{mg}$ of caffeine, $\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{N}_{4} \mathrm{O}_{2}$ . How many moles of caffeine are in a cup? How many molecules of caffeine?

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Problem 57

What is the mass in grams of each of the following samples?

(a) 0.0015 mol of sodium

(b) 0.0015 mol of lead

(c) 0.0015 mol of diazepam (Valium), $\mathrm{C}_{16} \mathrm{H}_{13} \mathrm{ClN}_{2} \mathrm{O}$

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Problem 58

A sample that weighs 25.12 $\mathrm{g}$ contains $6.022 \times 10^{23}$ particles. If 25.00$\%$ of the total number of particles are argon atoms and 75.00$\%$ are another element, what is the chemical identity of the other constituent?

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Problem 59

A sample that weighs 107.75 $\mathrm{g}$ is a mixture of 30$\%$ helium atoms and 70$\%$ krypton atoms. How many particles are present in the sample?

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Problem 60

Titanium metal is obtained from the mineral rutile, $\mathrm{TiO}_{2}$. How many kilograms of rutile are needed to produce 100.0 kg of Ti?

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Problem 61

Iron metal can be produced from the mineral hematite, $\mathrm{Fe}_{2} \mathrm{O}_{3},$ by reaction with carbon. How many kilograms of iron are present in 105 $\mathrm{kg}$ of hematite?

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Problem 62

In the preparation of iron from hematite (Problem 3.61$)$ $\mathrm{Fe}_{2} \mathrm{O}_{3}$ reacts with carbon:

$\mathrm{Fe}_{2} \mathrm{O}_{3}+\mathrm{C} \longrightarrow \mathrm{Fe}+\mathrm{CO}_{2} \quad$ Unbalanced

(a) Balance the equation.

(b) How many moles of carbon are needed to react with 525 $\mathrm{g}$ of hematite?

(c) How many grams of carbon are needed to react with 525 $\mathrm{g}$ of hematite?

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Problem 63

An alternative method for preparing pure iron from $\mathrm{Fe}_{2} \mathrm{O}_{3}$ (Problem 3.61$)$ is by reaction with carbon monoxide:

$\mathrm{Fe}_{2} \mathrm{O}_{3}+\mathrm{CO} \longrightarrow \mathrm{Fe}+\mathrm{CO}_{2} \quad$ Unbalanced

(a) Balance the equation.

(b) How many grams of CO are needed to react with 3.02 $\mathrm{g}$ of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ ?

(c) How many grams of $\mathrm{CO}$ are needed to react with 1.68 $\mathrm{mol}$ of $\mathrm{Fe}_{2} \mathrm{O}_{3} ?$

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Problem 64

Magnesium metal burns in oxygen to form magnesium oxide, MgO.

(a) Write a balanced equation for the reaction.

(b) How many grams of oxygen are needed to react with 25.0 g of Mg? How many grams of MgO will result?

(c) How many grams of Mg are needed to react with 25.0 g of $\mathrm{O}_{2} ?$ How many grams of MgO will result?

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Problem 65

Ethylene gas, $\mathrm{C}_{2} \mathrm{H}_{4},$ reacts with water at high temperature to yield ethyl alcohol, $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}$ .

(a) How many grams of ethylene are needed to react with 0.133 mol of $\mathrm{H}_{2} \mathrm{O}$ ? How many grams of ethyl alcohol will result?

(b) How many grams of water are needed to react with 0.371 mol of ethylene? How many grams of ethyl alcohol will result?

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Problem 66

Pure oxygen was first made by heating mercury(II) oxide:

$\mathrm{HgO} \stackrel{\text { Heat }}{\longrightarrow} \mathrm{Hg}+\mathrm{O}_{2} \quad$ Unbalanced

(a) Balance the equation.

(b) How many grams of mercury and how many grams of oxygen are formed from 45.5 $\mathrm{g}$ of HgO?

(c) How many grams of HgO would you need to obtain 33.3 $\mathrm{g}$ of $\mathrm{O}_{2} ?$

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Problem 67

Titanium dioxide (TiO $_{2} ),$ the substance used as the pigment in white paint, is prepared industrially by reaction of $\mathrm{TiCl}_{4}$ with $\mathrm{O}_{2}$ at high temperature.

$\mathrm{TiCl}_{4}+\mathrm{O}_{2} \stackrel{\mathrm{Heat}}{\longrightarrow} \mathrm{TiO}_{2}+2 \mathrm{Cl}_{2}$

How many kilograms of $\mathrm{TiO}_{2}$ can be prepared from 5.60 $\mathrm{kg}$ of $\mathrm{TiCl}_{4} ?$

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Problem 68

Silver metal reacts with chlorine $\left(\mathrm{Cl}_{2}\right)$ to yield silver chloride. If 2.00 $\mathrm{g}$ of Ag reacts with 0.657 $\mathrm{g}$ of $\mathrm{Cl}_{2},$ what is the empirical formula of silver chloride?

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Problem 69

Aluminum reacts with oxygen to yield aluminum oxide. If 5.0 $\mathrm{g}$ of Al reacts with 4.45 $\mathrm{g}$ of $\mathrm{O}_{2},$ what is the empirical formula of aluminum oxide?

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Problem 70

The industrial production of hydriodic acid takes place bytreatment of iodine with hydrazine

$\left(\mathrm{N}_{2} \mathrm{H}_{4}\right) :$

$2 \mathrm{I}_{2}+\mathrm{N}_{2} \mathrm{H}_{4} \longrightarrow 4 \mathrm{HI}+\mathrm{N}_{2}$

(a) How many grams of $\mathrm{I}_{2}$ are needed to react with 36.7 $\mathrm{g}$ of $\mathrm{N}_{2} \mathrm{H}_{4} ?$

(b) How many grams of HI are produced from the reaction of 115.7 $\mathrm{g}$ of $\mathrm{N}_{2} \mathrm{H}_{4}$ with excess iodine?

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Problem 71

An alternative method for producing hydriodic acid (Problem 3.70 ) is the reaction of iodine with hydrogen sulfide:

$\mathrm{H}_{2} \mathrm{S}+\mathrm{I}_{2} \longrightarrow 2 \mathrm{HI}+\mathrm{S}$

(a) How many grams of $\mathrm{I}_{2}$ are needed to react with 49.2 $\mathrm{g}$ of $\mathrm{H}_{2} \mathrm{S}$ ?

(b) How many grams of HI are produced from the reaction of 95.4 $\mathrm{g}$ of $\mathrm{H}_{2} \mathrm{S}$ with excess $\mathrm{I}_{2} ?$

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Problem 72

Assume that you have 1.39 $\mathrm{mol}$ of $\mathrm{H}_{2}$ and 3.44 $\mathrm{mol}$ of $\mathrm{N}_{2}$ How many grams of ammonia (NH_ ) can you make, and how many grams of which reactant will be left over?

$$3 \mathrm{H}_{2}+\mathrm{N}_{2} \longrightarrow 2 \mathrm{NH}_{3}$$

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Problem 73

Hydrogen and chlorine react to yield hydrogen chloride: $\mathrm{H}_{2}+\mathrm{Cl}_{2} \rightarrow 2 \mathrm{HCl}$ . How many grams of $\mathrm{HCl}$ are formed from reaction of 3.56 $\mathrm{g}$ of $\mathrm{H}_{2}$ with 8.94 $\mathrm{g}$ of $\mathrm{Cl}_{2} ?$ Which reactant is limiting?

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Problem 74

How many grams of the dry-cleaning solvent $1,2$ -dichloroethane (also called ethylene chloride), $\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{Cl}_{2}$ can be prepared by reaction of 15.4 $\mathrm{g}$ of ethylene, $\mathrm{C}_{2} \mathrm{H}_{4}$ with 3.74 $\mathrm{g}$ of $\mathrm{Cl}_{2} ?$

$$\mathrm{C}_{2} \mathrm{H}_{4}+\mathrm{Cl}_{2} \longrightarrow \mathrm{C}_{2} \mathrm{H}_{4} \mathrm{Cl}_{2}$$

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Problem 75

How many grams of each product result from the following reactions, and how many grams of which reactant is left over?

(a) $(1.3 \mathrm{g} \mathrm{NaCl})+\left(3.5 \mathrm{g} \mathrm{AgNO}_{3}\right) \longrightarrow(x \mathrm{g} \mathrm{AgCl})+\left(y \mathrm{g} \mathrm{NaNO}_{3}\right)$

(b) $\left(2.65 \mathrm{g} \mathrm{BaCl}_{2}\right)+\left(6.78 \mathrm{g} \mathrm{H}_{2} \mathrm{SO}_{4}\right) \longrightarrow\left(x \mathrm{g} \mathrm{BaSO}_{4}\right)+(y \mathrm{g} \mathrm{HCl})$

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Problem 76

Nickel(II) sulfate, used for nickel plating, is prepared by treatment of nickel(II) carbonate with sulfuric acid:

$$\mathrm{NiCO}_{3}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{NiSO}_{4}+\mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}$$

(a) How many grams of $\mathrm{H}_{2} \mathrm{SO}_{4}$ are needed to react with 14.5 $\mathrm{g}$ of $\mathrm{NiCO}_{3} ?$

(b) How many grams of $\mathrm{NisO}_{4}$ are obtained if the yield is 78.9$\% ?$

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Problem 77

Hydrazine, $\mathrm{N}_{2} \mathrm{H}_{4},$ once used as a rocket propellant, reacts with oxygen:

$$\mathrm{N}_{2} \mathrm{H}_{4}+\mathrm{O}_{2} \longrightarrow \mathrm{N}_{2}+2 \mathrm{H}_{2} \mathrm{O}$$

(a) How many grams of $\mathrm{O}_{2}$ are needed to react with 50.0 $\mathrm{g}$ of $\mathrm{N}_{2} \mathrm{H}_{4}$ ?

(b) How many grams of $\mathrm{N}_{2}$ are obtained if the yield is 85.5$\% ?$

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Problem 78

Limestone (CaCO $_{3} )$ reacts with hydrochloric acid according to the equation $\mathrm{CaCO}_{3}+2 \mathrm{HCl} \rightarrow \mathrm{CaCl}_{2}+\mathrm{H}_{2} \mathrm{O}+$ $\mathrm{CO}_{2}$ . If 1.00 $\mathrm{mol}$ of $\mathrm{CO}_{2}$ has a volume of 22.4 $\mathrm{L}$ under the reaction conditions, how many liters of gas can be formed by reaction of 2.35 $\mathrm{g}$ of $\mathrm{CaCO}_{3}$ with 2.35 $\mathrm{g}$ of $\mathrm{HCl}$ ? Which reactant is limiting?

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Problem 79

Sodium azide (NaN $_{3} )$ yields $\mathrm{N}_{2}$ gas when heated to $300^{\circ} \mathrm{C},$ a reaction used in automobile air bags. If 1.00 $\mathrm{mol}$ of $\mathrm{N}_{2}$ has a volume of 47.0 $\mathrm{L}$ under the reaction conditions, how many liters of gas can be formed by heating 38.5 $\mathrm{g}$ of $\mathrm{NaN}_{3} ?$ The reaction is

$$2 \mathrm{NaN}_{3} \longrightarrow 3 \mathrm{N}_{2}(g)+2 \mathrm{Na}$$

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Problem 80

Acetic acid $\left(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\right)$ reacts with isopentyl alcohol

$\left(\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}\right)$ to yield isopentyl acetate $\left(\mathrm{C}_{7} \mathrm{H}_{14} \mathrm{O}_{2}\right),$ a fragrant substance with the odor of bananas. If the yield from the reaction of acetic acid with isopentyl alcohol is $45 \%, \mathrm{how}$ many grams of isopentyl acetate are formed from 3.58 $\mathrm{g}$ of acetic acid and 4.75 $\mathrm{g}$ of isopentyl alcohol? The reaction is

$$\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}+\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O} \longrightarrow \mathrm{C}_{7} \mathrm{H}_{14} \mathrm{O}_{2}+\mathrm{H}_{2} \mathrm{O}$$

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Problem 81

Cisplatin $\left[\operatorname{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\right],$ a compound used in cancer treatment, is prepared by reaction of ammonia with potassium tetrachloroplatinate:

$$\mathrm{K}_{2} \mathrm{PtC}_{4}+2 \mathrm{NH}_{3} \longrightarrow 2 \mathrm{KCl}+\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}$$

How many grams of cisplatin are formed from 55.8 $\mathrm{g}$ of $\mathrm{K}_{2} \mathrm{PtCl}_{4}$ and 35.6 $\mathrm{g}$ of $\mathrm{NH}_{3}$ if the reaction takes place in 95$\%$ yield based on the limiting reactant?

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Problem 82

If 1.87 g of acetic acid reacts with 2.31 $\mathrm{g}$ of isopentyl alcohol to give 2.96 $\mathrm{g}$ of isopentyl acetate (Problem $3.80 ),$ what is the percent yield of the reaction?

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Problem 83

If 3.42 $\mathrm{g}$ of $\mathrm{K}_{2} \mathrm{PtCl}_{4}$ and 1.61 $\mathrm{g}$ of $\mathrm{NH}_{3}$ give 2.08 $\mathrm{g}$ of cisplatin (Problem $3.81 ),$ what is the percent yield of the reaction?

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Problem 84

How many moles of solute are present in each of the fol- lowing solutions?

(a) 35.0 $\mathrm{mL}$ of 1.200 $\mathrm{M} \mathrm{HNO}_{3}$

(b) 175 $\mathrm{mL}$ of 0.67 $\mathrm{M}$ glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$

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Problem 85

How many grams of solute would you use to prepare each of the following solutions?

(a) 250.0 $\mathrm{mL}$ of 0.600 $\mathrm{M}$ ethyl alcohol ( $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O} )$

(b) 167 $\mathrm{mL}$ of 0.200 $\mathrm{M}$ boric acid $\left(\mathrm{H}_{3} \mathrm{BO}_{3}\right)$

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Problem 86

How many milliliters of a 0.45 $\mathrm{M} \mathrm{BaCl}_{2}$ solution contain 15.0 $\mathrm{g}$ of $\mathrm{BaCl}_{2} ?$

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Problem 87

How many milliliters of a 0.350 $\mathrm{M}$ KOH solution contain 0.0171 $\mathrm{mol}$ of $\mathrm{KOH}$ ?

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Problem 88

The sterile saline solution used to rinse contact lenses can be made by dissolving 400 $\mathrm{mg}$ of NaCl in sterile water and diluting to 100 $\mathrm{mL}$ . What is the molarity of the solution?

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Problem 89

The concentration of glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ in normal blood is approximately 90 $\mathrm{mg}$ per 100 $\mathrm{mL}$ . What is the molarity of the glucose

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Problem 90

Copper reacts with dilute nitric acid according to the following equation:

$3 \mathrm{Cu}(s)+8 \mathrm{HNO}_{3}(a q) \longrightarrow$ $3 \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}(a q)+2 \mathrm{NO}(g)+4 \mathrm{H}_{2} \mathrm{O}(l)$

If a copper penny weighing 3.045 g is dissolved in a small amount of nitric acid and the resultant solution is diluted to 50.0 $\mathrm{mL}$ with water, what is the molarity of the $\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2} ?$

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Problem 91

Pennies minted after 1982 are mostly zinc (97.5%) with a copper cover. If a post-1982 penny is dissolved in a small amount of nitric acid, the copper coating reacts as in Problem 3.90 and the exposed zinc reacts according to the following equation:

$$\mathrm{Zn}(\mathrm{s})+2 \mathrm{HNO}_{3}(a q) \longrightarrow \mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\mathrm{H}_{2}(g)$$

For a penny that weighs $2.482 \mathrm{g},$ what is the molarity of the

$\mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2}$ if the resultant solution is diluted to 250.0 $\mathrm{mL}$ with water?

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Problem 92

A bottle of 12.0 M hydrochloric acid has only 35.7 mL left in it. What will the HCl concentration be if the solution is diluted to 250.0 mL?

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Problem 93

What is the volume of the solution that would result by diluting 70.00 mL of 0.0913 M NaOH to a concentration of 0.0150 M?

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Problem 94

A flask containing 450 $\mathrm{mL}$ of 0.500 $\mathrm{M}$ HBr was accidentally knocked to the floor. How many grams of $\mathrm{K}_{2} \mathrm{CO}_{3}$ would you need to put on the spill to neutralize the acid according to the following equation?

$2 \mathrm{HBr}(a q)+\mathrm{K}_{2} \mathrm{CO}_{3}(a q) \longrightarrow 2 \mathrm{KBr}(a q)+\mathrm{CO}_{2}(g)+\mathrm{H}_{2} \mathrm{O}(l)$

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Problem 95

The odor of skunks is caused by chemical compounds called thiols. These compounds, of which butanethiol $\left(\mathrm{C}_{4} \mathrm{H}_{10} \mathrm{S}\right)$ is a representative example, can be deodorized by reaction with household bleach (NaOCl) according to the following equation:

$2 \mathrm{C}_{4} \mathrm{H}_{10} \mathrm{S}+\mathrm{NaOCl}(a q) \longrightarrow \mathrm{C}_{8} \mathrm{H}_{18} \mathrm{S}_{2}+\mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}(a q)$

How many grams of butanethiol can be deodorized by reaction with 5.00 $\mathrm{mL}$ of 0.0985 $\mathrm{M} \mathrm{NaOCl}$ ?

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Problem 96

Potassium permanganate $\left(\mathrm{KMnO}_{4}\right)$ reacts with oxalic acid $\left(\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}\right)$ in aqueous sulfuric acid according to the following equation:

$2 \mathrm{KMnO}_{4}+5 \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}+3 \mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow$

$\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad$$2 \mathrm{MnSO}_{4}+10 \mathrm{CO}_{2}+8 \mathrm{H}_{2} \mathrm{O}+\mathrm{K}_{2} \mathrm{SO}_{4}$

How many milliliters of a 0.250 $\mathrm{M} \mathrm{KMnO}_{4}$ solution are needed to react completely with 3.225 $\mathrm{g}$ of oxalic acid?

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Problem 97

Oxalic acid, $\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4},$ is a toxic substance found in spinach leaves. What is the molarity of a solution made by dissolving 12.0 $\mathrm{g}$ of oxalic acid in enough water to give 400.0 $\mathrm{mL}$ of solution? How many milliters of 0.100 $\mathrm{M} \mathrm{KOH}$ would you need to titrate 25.0 $\mathrm{mL}$ of the oxalic acid solution according to the following equation?

$$\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(a q)+2 \mathrm{KOH}(a q) \longrightarrow \mathrm{K}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l)$$

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Problem 98

Urea, a substance commonly used as a fertilizer, has the formula $\mathrm{CH}_{4} \mathrm{N}_{2} \mathrm{O}$ . What is its percent composition by mass?

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Problem 99

Calculate the mass percent composition of each of the following substances:

(a) Malachite, a copper-containing mineral: $\mathrm{C} \mathrm{u}_{2}(\mathrm{OH})_{2} \mathrm{CO}_{3}$

(b) Acetaminophen, a headache remedy: $\mathrm{C}_{8} \mathrm{H}_{9} \mathrm{NO}_{2}$

(c) Prussian blue, an ink pigment: Fe_{l} [ \mathrm { Fe } ( \mathrm { CN } ) _ { 6 } ] _ { 3 }

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Problem 100

An unknown liquid is composed of 5.57% H, 28.01% Cl, and 66.42% C. The molecular mass found by mass spectrometry is 126.58 amu. What is the molecular formula of the compound?

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Problem 101

An unknown liquid is composed of 34.31% C, 5.28% H, and 60.41% I. The molecular mass found by mass spectrometry is 210.06 amu. What is the molecular formula of the compound?

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Problem 102

What is the empirical formula of stannous fluoride, the first fluoride compound added to toothpaste to protect teeth against decay? Its mass percent composition is 24.25% F, 75.75% Sn.

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Problem 103

What are the empirical formulas of each of the following substances?

(a) Ibuprofen, a headache remedy: 75.69% C, 15.51% O, 8.80% H

(b) Magnetite, a naturally occurring magnetic mineral: 72.36% Fe, 27.64% O

(c) Zircon, a mineral from which cubic zirconia is made: 34.91% O, 15.32% Si, 49.77% Zr

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Problem 104

Combustion analysis of 45.62 $\mathrm{mg}$ of toluene, a commonly used solvent, gives 35.67 $\mathrm{mg}$ of $\mathrm{H}_{2} \mathrm{O}$ and 152.5 $\mathrm{mg}$ of $\mathrm{CO}_{2}$ What is the empirical formula of toluene?

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Problem 105

Conine, a toxic substance isolated from poison hemlock, contains only carbon, hydrogen, and nitrogen. Combustion analysis of a 5.024 $\mathrm{mg}$ sample yields 13.90 $\mathrm{mg}$ of $\mathrm{CO}_{2}$ and 6.048 $\mathrm{mg}$ of $\mathrm{H}_{2} \mathrm{O}$ . What is the empirical formula of conine?

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Problem 106

Cytochrome $c$ is an iron-containing enzyme found in the cells of all aerobic organisms. If cytochrome $c$ is 0.43$\%$ Fe by mass, what is its minimum molecular mass?

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Problem 107

Nitrogen fixation in the root nodules of peas and other leguminous plants is carried out by the molybdenumcontaining enzyme nitrogenase. What is the molecular mass of nitrogenase if the enzyme contains two molybdenum atoms and is 0.0872% Mo by mass?

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Problem 108

Disilane, $\mathrm{Si}_{2} \mathrm{H}_{x y}$ is analyzed and found to contain 90.28$\%$ silicon by mass. What is the value of $x ?$

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Problem 109

A certain metal sulfide, $\mathrm{MS}_{2},$ is used extensively as a high-temperature lubricant. If $\mathrm{MS}_{2}$ is 40.06$\%$ sulfur by mass, what is the identity of the metal M?

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Problem 110

The mass of an organic compound was found by mass spectrometry to be 70.04211 amu. Is the sample $\mathrm{C}_{5} \mathrm{H}_{10}$ $\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O},$ or $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{N}_{2} ?$ Exact masses of elements are: 1.007825 $\left(^{1} \mathrm{H}\right) ; 12.00000\left(\mathrm{C}^{12} \mathrm{C}\right) ; 14.003074(14 \mathrm{N}) ; 15.994915\left(^{16} \mathrm{O}\right)$

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Problem 111

The mass of an organic compound was found by mass spectrometry to be 58.07746 amu. Is the sample $\mathrm{C}_{4} \mathrm{H}_{10}$ $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O},$ or $\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{N}_{2} ?$ Exact masses of elements are: 1.007825 $\left(^{1} \mathrm{H}\right) ; 12.00000\left(\mathrm{C}^{12} \mathrm{C}\right) ; 14.003074(14 \mathrm{N}) ; 15.994915\left(^{16} \mathrm{O}\right)$

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Problem 112

Combustion analysis of a 31.472 $\mathrm{mg}$ sample of the widely used flame retardant Decabrom gave 1.444 $\mathrm{mg}$ of $\mathrm{CO}_{2}$ . Is the molecular formula of Decabrom $\mathrm{C}_{12} \mathrm{Br}_{10}$ or $\mathrm{C}_{12} \mathrm{Br}_{10} \mathrm{O}$ ?

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Problem 113

The stimulant amphetamine contains only carbon, hydrogen, and nitrogen. Combustion analysis of a 42.92 $\mathrm{mg}$ sample of amphetamine gives 37.187 $\mathrm{mg}$ of $\mathrm{H}_{2} \mathrm{O}$ and 125.75 $\mathrm{mg}$ of $\mathrm{CO}_{2}$ . If the molar mass of amphetamine is less than 160 $\mathrm{g} / \mathrm{mol}$ , what is its molecular formula?

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Problem 114

Ringer’s solution, used in the treatment of burns and wounds, is prepared by dissolving 4.30 g of NaCl, 0.150 g of KCl, and 0.165 g of CaCl2 in water and diluting to a volume of 500.0 mL. What is the molarity of each of the component ions in the solution?

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Problem 115

Balance the following equations:

(a) $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NO}_{2}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O}+\mathrm{NO}_{2}$

(b) Au $+\mathrm{H}_{2} \mathrm{SeO}_{4} \longrightarrow \mathrm{Au}_{2}\left(\mathrm{SeO}_{4}\right)_{3}+\mathrm{H}_{2} \mathrm{SeO}_{3}+\mathrm{H}_{2} \mathrm{O}$

(c) $\mathrm{NH}_{4} \mathrm{ClO}_{4}+\mathrm{Al} \longrightarrow \mathrm{Al}_{2} \mathrm{O}_{3}+\mathrm{N}_{2}+\mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{O}$

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Problem 116

The estimated concentration of gold in the oceans is $1.0 \times 10^{-11} \mathrm{g} / \mathrm{mL}$ .

(a) Express the concentration in mol/L.

(b) Assuming that the volume of the oceans is $1.3 \times 10^{21} \mathrm{L}$ estimate the amount of dissolved gold in grams in the oceans.

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Problem 117

Silver sulfide, the tarnish on silverware, comes from reac- tion of silver metal with hydrogen sulfide $\left(\mathrm{H}_{2} \mathrm{S}\right)$ :

$$\mathrm{Ag}+\mathrm{H}_{2} \mathrm{S}+\mathrm{O}_{2} \longrightarrow \mathrm{Ag}_{2} \mathrm{S}+\mathrm{H}_{2} \mathrm{O} \text { Unbalanced }$$

(a) Balance the equation.

(b) If the reaction were used intentionally to prepare $\mathrm{Ag}_{2} \mathrm{S}$ , how many grams would be formed from 496 g of Ag, 80.0 $\mathrm{g}$ of $\mathrm{H}_{2} \mathrm{S},$ and 40.0 $\mathrm{g}$ of $\mathrm{O}_{2}$ if the reaction takes place in 95$\%$ yield based on the limiting reactant?

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Problem 118

Give the percent composition of each of the following substances:

(a) Glucose, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$

(b) Sulfuric acid, $\mathrm{H}_{2} \mathrm{SO}_{4}$

(c) Potassium permanganate, KMnO_{4}

(d) Saccharin, $\mathrm{C}_{7} \mathrm{H}_{5} \mathrm{NO}_{3} \mathrm{S}$

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Problem 119

What are the empirical formulas of substances with the following mass percent compositions?

(a) Aspirin: $4.48 \% \mathrm{H}, 60.00 \% \mathrm{C}, 35.52 \% \mathrm{O}$

(b) Ilmenite (a titanium-containing ore): $31.63 \% \mathrm{O}, 31.56 \%$ Ti, 36.81$\% \mathrm{Fe}$

(c) Sodium thiosulfate (photographic "fixer"): 30.36$\% \mathrm{O}$ , $29.08 \% \mathrm{Na}, 40.56 \% \mathrm{S}$

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Problem 120

The reaction of tungsten hexachloride (WCl_ ) with bismuth gives hexatungsten dodecachloride $\left(\mathrm{W}_{6} \mathrm{Cl}_{12}\right)$

$\mathrm{WCl}_{6}+\mathrm{Bi} \longrightarrow \mathrm{W}_{6} \mathrm{Cl}_{12}+\mathrm{BiCl}_{3}$ Unbalanced

(a) Balance the equation.

(b) How many grams of bismuth react with 150.0 $\mathrm{g}$ of $\mathrm{WCl}_{6} ?$

(c) When 222 $\mathrm{g}$ of $\mathrm{WCl}_{6}$ react with 175 $\mathrm{g}$ of Bi, how much $\mathrm{W}_{6} \mathrm{Cl}_{12}$ is formed based on the limiting reactant?

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Problem 121

Sodium borohydride, NaBH_ a substance used in the synthesis of many pharmaceutical agents, can be prepared by reaction of NaH with $\mathrm{B}_{2} \mathrm{H}_{6}$ according to the equation $2 \mathrm{NaH}+\mathrm{B}_{2} \mathrm{H}_{6} \rightarrow 2 \mathrm{NaBH}_{4}$

(a) How many grams of NaBH_ can be prepared by reaction between 8.55 $\mathrm{g}$ of NaH and 6.75 $\mathrm{g}$ of $\mathrm{B}_{2} \mathrm{H}_{6} ?$

(b) Which reactant is limiting, and how many grams of the excess reactant will be left over?

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Problem 122

Ferrocene, a substance proposed for use as a gasoline addi- tive, has the percent composition 5.42% H, 64.56% C, and 30.02% Fe. What is the empirical formula of ferrocene?

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Problem 123

The molar mass of $\mathrm{HCl}$ is 36.5 $\mathrm{g} / \mathrm{mol}$ , and the average mass per $\mathrm{HCl}$ molecule is 36.5 $\mathrm{amu}$ . Use the fact that $1 \mathrm{amu}=1.6605 \times 10^{-24} \mathrm{g}$ to calculate Avogadro's number.

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Problem 124

What is the molarity of each ion in a solution prepared by dissolving 0.550 $\mathrm{g}$ of $\mathrm{Na}_{2} \mathrm{SO}_{4}, 1.188 \mathrm{g}$ of $\mathrm{Na}_{3} \mathrm{PO}_{4}$ , and 0.223 $\mathrm{g}$ of $\mathrm{Li}_{2} \mathrm{SO}_{4}$ in water and diluting to a volume of 100.00 $\mathrm{mL} ?$

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Problem 125

Ethylene glycol, commonly used as automobile antifreeze, contains only carbon, hydrogen, and oxygen. Combustion analysis of a 23.46 $\mathrm{mg}$ sample yields 20.42 $\mathrm{mg}$ of $\mathrm{H}_{2} \mathrm{O}$ and 33.27 $\mathrm{mg}$ of $\mathrm{CO}_{2}$ . What is the empirical formula of ethylene glycol? What is its molecular formula if it has a molecular mass of 62.0 amu?

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Problem 126

The molecular mass of ethylene glycol (Problem 3.125$)$ is 62.0689 amu when calculated using the atomic masses found in a standard periodic table, yet the molecular mass determined experimentally by high-resolution mass spectrometry is 62.0368 amu. Explain the discrepancy.

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Problem 127

Balance the following equations:

(a) $\mathrm{CO}\left(\mathrm{NH}_{2}\right)_{2}(a q)+\mathrm{HOCl}(a q) \longrightarrow \mathrm{CO}_{2}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$

(b) $\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}(s)+\mathrm{SiO}_{2}(s)+\mathrm{C}(s) \longrightarrow$ $\mathrm{P}_{4}(g)+\mathrm{CaSiO}_{3}(l)+\mathrm{CO}(g)$

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Problem 128

Assume that gasoline has the formula $\mathrm{C}_{8} \mathrm{H}_{18}$ and has a density of 0.703 $\mathrm{g} / \mathrm{mL}$ . How many pounds of $\mathrm{CO}_{2}$ are produced from the complete combustion of 1.00 gal of gasoline?

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Problem 129

A sample of $\mathrm{CaCO}_{3}$ with a mass of 6.35 $\mathrm{g}$ is placed in 500.0 $\mathrm{mL}$ of 0.31 $\mathrm{M} \mathrm{HCl}$ , forming $\mathrm{CaCl}_{2}, \mathrm{H}_{2} \mathrm{O}$ , and $\mathrm{CO}_{2}$ What mass in grams of $\mathrm{CO}_{2}$ is produced?

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Problem 130

Compound $X$ contains only carbon, hydrogen, nitrogen, and chlorine. When 1.00 $\mathrm{g}$ of $\mathrm{X}$ is dissolved in water and allowed to react with excess silver nitrate, AgNO $_{3},$ all the chlorine in $\mathrm{X}$ reacts and 1.95 $\mathrm{g}$ of solid AgCl is formed. When 1.00 $\mathrm{g}$ of $\mathrm{X}$ undergoes complete combustion, 0.900 $\mathrm{g}$ of $\mathrm{CO}_{2}$ and 0.735 $\mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O}$ are formed. What is the empirical formula of $\mathrm{X} ?$

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Problem 131

A pulverized rock sample believed to be pure calcium carbonate, $\mathrm{CaCO}_{3},$ is subjected to chemical analysis and found to contain $51.3 \% \mathrm{Ca}, 7.7 \% \mathrm{C},$ and 41.0$\% \mathrm{O}$ by mass. Why can't this rock sample be pure $\mathrm{CaCO}_{3} ?$

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Problem 132

Salicylic acid, used in the manufacture of aspirin, contains only the elements $\mathrm{C}, \mathrm{H},$ and $\mathrm{O}$ and has only one acidic hydrogen that reacts with NaOH. When 1.00 $\mathrm{g}$ of salicylic acid undergoes complete combustion, 2.23 $\mathrm{g} \mathrm{CO}_{2}$ and 0.39 $\mathrm{g} \mathrm{H}_{2} \mathrm{O}$ are obtained. When 1.00 $\mathrm{g}$ of salicylic acid is titrated with $0.100 \mathrm{M} \mathrm{NaOH}, 72.4 \mathrm{mL}$ of base is needed for complete reaction. What are the empirical and molecular formulas of salicylic acid?

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Problem 133

Compound $X$ contains only the elements $\mathrm{C}, \mathrm{H}, \mathrm{O},$ and $\mathrm{S}$ . A 5.00 $\mathrm{g}$ sample undergoes complete combustion to give 4.83 $\mathrm{g}$ of $\mathrm{CO}_{2}, 1.48 \mathrm{g}$ of $\mathrm{H}_{2} \mathrm{O},$ and a certain amount of $\mathrm{SO}_{2}$ that is further oxidized to $\mathrm{SO}_{3}$ and dissolved in water to form sulfuric acid, $\mathrm{H}_{2} \mathrm{SO}_{4}$ . On titration of the $\mathrm{H}_{2} \mathrm{SO}_{4}$ 109.8 $\mathrm{mL}$ of 1.00 $\mathrm{M} \mathrm{NaOH}$ is needed for complete reaction. (Both $\mathrm{H}$ atoms in sulfuric acid are acidic and react with $\mathrm{NaOH} .$ )

(a) What is the empirical formula of $X ?$

(b) When 5.00 $\mathrm{g}$ of $\mathrm{X}$ is titrated with NaOH, it is found that $\mathrm{X}$ has two acidic hydrogens that react with NaOH and that 54.9 $\mathrm{mL}$ of 1.00 $\mathrm{M} \mathrm{NaOH}$ is required to completely neutralize the sample. What is the molecular formula of $\mathrm{X} ?$

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Problem 134

Assume that you have 1.00 $\mathrm{g}$ of a mixture of benzoic acid (molec. mass $=122 \mathrm{amu}$ ) and gallic acid (molec. mass $=170 \mathrm{amu}$ ), both of which contain one acidic hydrogen that reacts with NaOH. On titrating the mixture with $0.500 \mathrm{M} \mathrm{NaOH}, 14.7 \mathrm{mL}$ of base is needed to completely react with both acids. What mass in grams of each acid is present in the original mixture?

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Problem 135

A certain alcoholic beverage contains only ethanol $\left(\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}\right)$ and water. When a sample of this beverage undergoes combustion, the ethanol burns but the water simply evaporates and is collected along with the water produced by combustion. The combustion reaction is

$$\mathrm{C}_{2} \mathrm{H}_{6} \mathrm{O}(l)+3 \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{CO}_{2}(g)+3 \mathrm{H}_{2} \mathrm{O}(g)$$

When a 10.00 g sample of this beverage is burned, 11.27 $\mathrm{g}$ of water is collected. What is the mass in grams of ethanol, and what is the mass of water in the original sample?

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Problem 136

A mixture of FeO and $\mathrm{Fe}_{2} \mathrm{O}_{3}$ with a mass of 10.0 $\mathrm{g}$ is converted to 7.43 $\mathrm{g}$ of pure Fe metal. What are the amounts in grams of $\mathrm{FeO}$ and $\mathrm{Fe}_{2} \mathrm{O}_{3}$ in the original sample?

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Problem 137

A compound of formula $X \mathrm{Cl}_{3}$ reacts with aqueous AgNO $_{3}$ to yield solid AgCl according to the following equation:

$$\mathrm{XCl}_{3}(a q)+3 \mathrm{AgNO}_{3}(a q) \longrightarrow \mathrm{X}\left(\mathrm{NO}_{3}\right)_{3}(a q)+3 \mathrm{AgCl}(s)$$

When a solution containing 0.634 $\mathrm{g}$ of $\mathrm{XCl}_{3}$ was allowed to react with an excess of aqueous AgNO $_{3}, 1.68 \mathrm{g}$ of solid $\mathrm{AgCl}$ was formed. What is the identity of the atom $\mathrm{X}$ ?

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Problem 138

When eaten, dietary carbohydrates are digested to yield glucose $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right),$ which is then metabolized to yield carbon dioxide and water:

$\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+\mathrm{O}_{2} \longrightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O} \quad$ Unbalanced

Balance the equation, and calculate both the mass in grams and the volume in liters of the $\mathrm{CO}_{2}$ produced from 66.3 $\mathrm{g}$ of glucose, assuming that 1 $\mathrm{mol}$ of $\mathrm{CO}_{2}$ has a volume of 25.4 $\mathrm{L}$ at normal body temperature.

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Problem 139

Other kinds of titrations are possible in addition to acid-base titrations. For example, the concentration of a solution of potassium permanganate, KMnO, can be determined by titration against a known amount of oxalic acid, $\mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}$ according to the following equation:

$$\begin{array}{c}{5 \mathrm{H}_{2} \mathrm{C}_{2} \mathrm{O}_{4}(a q)+2 \mathrm{KMnO}_{4}(a q)+3 \mathrm{H}_{2} \mathrm{SO}_{4}(a q) \longrightarrow} \\ \quad\quad\quad\quad\quad\quad\quad\quad\quad\quad\quad {10 \mathrm{CO}_{2}(g)+2 \mathrm{MnSO}_{4}(a q)+\mathrm{K}_{2} \mathrm{SO}_{4}(a q)+8 \mathrm{H}_{2} \mathrm{O}(l)}\end{array}$$

What is the concentration of a KMnO, solution if 22.35 $\mathrm{mL}$ reacts with 0.5170 $\mathrm{g}$ of oxalic acid?

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Problem 140

A copper wire having a mass of 2.196 $\mathrm{g}$ was allowed to react with an excess of sulfur. The excess sulfur was then burned, yielding $\mathrm{SO}_{2}$ gas. The mass of the copper sulfide produced was 2.748 $\mathrm{g}$

(a) What is the percent composition of copper sulfide?

(b) What is its empirical formula?

(c) Calculate the number of copper ions per cubic centimeter if the density of the copper sulfide is 5.6 $\mathrm{g} / \mathrm{cm}^{3}$ .

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Problem 141

Element $X,$ a member of group 5 $\mathrm{A}$ , forms two chlorides, $\mathrm{XCl}_{3}$ and $\mathrm{XCl}_{5}$ . Reaction of an excess of $\mathrm{Cl}_{2}$ with 8.729 $\mathrm{g}$ of $\mathrm{XCl}_{3}$ yields 13.233 $\mathrm{g}$ of $\mathrm{XCl}_{5} .$ What is the atomic mass and the identity of the element $\mathrm{X}$ ?

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Problem 142

A mixture of $X \mathrm{Cl}_{3}$ and $\mathrm{XCl}_{5}(\text { see Problem } 3.141)$ weighing 10.00 $\mathrm{g}$ contains 81.04$\% \mathrm{Cl}$ by mass. How many grams of $\mathrm{XCl}_{3}$ and how many grams of $\mathrm{XCl}_{5}$ are present in the mixture?

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Problem 143

A 1.268 g sample of a metal carbonate (MCO $_{3} )$ was treated with 100.00 $\mathrm{mL}$ of 0.1083 M sulfuric acid $\left(\mathrm{H}_{2} \mathrm{SO}_{4}\right),$ yielding $\mathrm{CO}_{2}$ gas and an aqueous solution of the metal sulfate $\left(\mathrm{MSO}_{4}\right) .$ The solution was boiled to remove all the dissolved $\mathrm{CO}_{2}$ and was then titrated with 0.1241 $\mathrm{M} \mathrm{NaOH}$ . A 71.02 $\mathrm{mL}$ volume of NaOH was required to neutralize the excess $\mathrm{H}_{2} \mathrm{SO}_{4}$

(a) What is the identity of the metal M?

(b) How many liters of $\mathrm{CO}_{2}$ gas were produced if the density of $\mathrm{CO}_{2}$ is 1.799 $\mathrm{g} / \mathrm{L}$ ?

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Problem 144

Ammonium nitrate, a potential ingredient of terrorist bombs, can be made nonexplosive by addition of diammonium hydrogen phosphate, $\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4}$ . Analysis of such a $\mathrm{NH}_{4} \mathrm{NO}_{3}-\left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4}$ mixture showed the mass percent of nitrogen to be 30.43$\%$ . What is the mass ratio of the two

components in the mixture?

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Problem 145

Window glass is typically made by mixing soda ash $\left(\mathrm{Na}_{2} \mathrm{CO}_{3}\right),$ limestone $\left(\mathrm{CaCO}_{3}\right),$ and silica sand $\left(\mathrm{SiO}_{2}\right)$ and then heating to 1500 ' $\mathrm{C}$ to drive off $\mathrm{CO}_{2}$ from the $\mathrm{Na}_{2} \mathrm{CO}_{3}$ and $\mathrm{CaCO}_{3} .$ The resultant glass consists of about 12$\% \mathrm{Na}_{2} \mathrm{O}$ by mass, 13$\% \mathrm{CaO}$ by mass, and 75$\% \mathrm{SiO}_{2}$ by mass. How much of each reactant would you start with to prepare 0.35 $\mathrm{kg}$ of glass?

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Problem 146

An unidentified metal M reacts with an unidentified halogen $X$ to form a compound $M X_{2}$ . When heated, the compound decomposes by the reaction:

$$2 \mathrm{MX}_{2}(s) \longrightarrow 2 \mathrm{MX}(s)+\mathrm{X}_{2}(g)$$

When 1.12 g of $\mathrm{MX}_{2}$ is heated, 0.720 $\mathrm{g}$ of $\mathrm{MX}$ is obtained, along with 56.0 $\mathrm{mL}$ of $\mathrm{X}_{2}$ gas. Under the conditions used, 1.00 $\mathrm{mol}$ of the gas has a volume of 22.41 $\mathrm{L}$ .

(a) What is the atomic mass and identity of the halogen X?

(b) What is the atomic mass and identity of the metal M?

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Problem 147

A compound with the formula $\mathrm{XOCl}_{2}$ reacts with water, yielding HCl and another acid $\mathrm{H}_{2} \mathrm{XO}_{3},$ which has two acidic hydrogens that react with NaOH. When 0.350 g of $\mathrm{XOCl}_{2}$ was added to 50.0 $\mathrm{mL}$ of water and the resultant solution was titrated, 96.1 $\mathrm{mL}$ of 0.1225 $\mathrm{M} \mathrm{NaOH}$ was required to react with all the acid.

(a) Write a balanced equation for the reaction of $\mathrm{XOCl}_{2}$ with $\mathrm{H}_{2} \mathrm{O}$ .

(b) What are the atomic mass and identity of element X?

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Problem 148

Element $M$ is prepared industrially by a two-step procedure according to the following (unbalanced) equations:

$$\begin{array}{l}{\text { (1) } \mathrm{M}_{2} \mathrm{O}_{3}(s)+\mathrm{C}(s)+\mathrm{Cl}_{2}(g) \longrightarrow \mathrm{MCl}_{3}(l)+\mathrm{CO}(g)} \\ {\text { (2) } \mathrm{MCl}_{3}(l)+\mathrm{H}_{2}(g) \longrightarrow \mathrm{M}(s)+\mathrm{HCl}(g)}\end{array}$$

Assume that 0.855 g of $\mathrm{M}_{2} \mathrm{O}_{3}$ is submitted to the reaction sequence. When the HCl produced in step (2) is dissolved in water and titrated with $0.511 \mathrm{M} \mathrm{NaOH}, 144.2 \mathrm{mL}$ of the NaOH solution is required to neutralize the HCl.

(a) Balance both equations.

(b) What is the atomic mass of element $M,$ and what is its identity?

(c) What mass of M in grams is produced in the reaction?

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