Introductory Chemistry: An Active Learning Approach

Mark S. Cracolice, Edward I. Peters

Chapter 10

Quantity Relationships in Chemical Reactions - all with Video Answers

Educators

Chapter Questions

Problem 1

The first step in the Ostwald process for manufacturing nitric acid is the reaction between ammonia and oxygen described by the equation $4 \mathrm{NH}_{3}+5 \mathrm{O}_{2} \rightarrow 4 \mathrm{NO}+6 \mathrm{H}_{2} \mathrm{O} .$ Use this equation
to answer all parts of this question.
a) How many moles of ammonia will react with 95.3 moles of oxygen?
b) How many moles of nitrogen monoxide will result from the reaction of 2.89 moles of ammonia?
c) If 3.35 moles of water is produced, how many moles of nitro-
gen monoxide will also be produced?

Ronald Prasad

Ronald Prasad

Numerade Educator

Problem 2

When hvdrogen sulfide reacts with oxygen, water and sulfur dioxide are produced. The balanced equation for this reaction is $2 \mathrm{H}_{2} \mathrm{S}(\mathrm{g})+3 \mathrm{O}_{2}(\mathrm{g}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\ell)+2 \mathrm{SO}_{2}(\mathrm{g}) .$ For all parts of
this question, consider what will happen if 4 moles of hydrogen sulfide react.
a) How many moles of oxygen are consumed?
b) How many moles of water are produced?
c) How many moles of sulfur dioxide are produced?

Ronald Prasad

Numerade Educator

Problem 3

Magnesium hydroxide is formed from the reaction of magnesium oxide and water. How many moles of magnesium oxide are needed to form 0.884 mole of magnesium hydroxide, when the oxide added to excess water?

Ronald Prasad

Numerade Educator

Problem 4

In our bodies, sugar is broken down by reacting with oxygen to produce water and carbon dioxide. How many moles of carbon dioxide will be formed upon the complete reaction of 0.424 moles glucose sugar $\left(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}\right)$ with excess oxygen gas?

Ronald Prasad

Numerade Educator

Problem 5

When sulfur dioxide reacts with oxygen, sulfur trioxide forms. How many moles of sulfur dioxide are needed to produce
3.99 moles of sulfur trioxide if the reaction is carried out in excess oxygen?

Ronald Prasad

Numerade Educator

Problem 6

Aqueous solutions of potassium hydrogen sulfate and potassium hydroxide react to form aqueous potassium sulfate and liquid water. How many moles of potassium hydroxide are necessary to form 0.636 moles of potassium sulfate?

Ronald Prasad

Numerade Educator

Problem 7

The first step in the Ostwald process for manufacturing nitric acid is the reaction between ammonia and oxygen described by the equation $4 \mathrm{NH}_{3}+5 \mathrm{O}_{2} \rightarrow 4 \mathrm{NO}+6 \mathrm{H}_{2} \mathrm{O} .$ Use this equation
to answer all parts of this question.a) How many moles of ammonia can be oxidized by 268 grams of oxygen?
b) If the reaction consumes 31.7 moles of ammonia, how many grams of water will be produced?
c) How many grams of ammonia are required to produce 404 grams of nitrogen monoxide?
d) If 6.41 grams of water result from the reaction, what will be the yield of nitrogen monoxide (in grams)?

Ronald Prasad

Numerade Educator

Problem 8

Butane, $C_{4} \mathrm{H}_{10}$, is a common fuel used for heating homes in areas not served by natural gas. The equation for its combustion is $2 \mathrm{C}_{4} \mathrm{H}_{10}+13 \mathrm{O}_{2} \rightarrow 8 \mathrm{CO}_{2}+10 \mathrm{H}_{2} \mathrm{O} .$ All parts of this question are related to this reaction.a) How many grams of butane can be burned by 1.42 moles of oxygen?
b) If 9.43 grams of oxygen is used in burning butane, how many moles of water result?
c) Calculate the number of grams of carbon dioxide that will be produced by burning 78.4 grams of butane.
d) How many grams of oxygen are used in a reaction that produces 43.8 grams of water?

Ronald Prasad

Numerade Educator

Problem 9

The explosion of nitroglycerine is described by the equation $4 \mathrm{C}_{3} \mathrm{H}_{5}\left(\mathrm{NO}_{3}\right)_{3} \rightarrow 12 \mathrm{CO}_{2}+10 \mathrm{H}_{2} \mathrm{O}+6 \mathrm{N}_{2}+\mathrm{O}_{2} .$ How many grams of carbon dioxide are produced by the explosion of 21.0 grams of nitroglycerine?

Ronald Prasad

Numerade Educator

Problem 10

According to the reaction $2 \mathrm{AgNO}_{3}+\mathrm{Cu} \rightarrow \mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}+$$2 \mathrm{Ag}$
.how many grams of copper(il) nitrate will be formed upon the complete reaction of 26.8 grams of copper with excess silver nitrate?

Ronald Prasad

Numerade Educator

Problem 11

Soaps are produced by the reaction of sodium hydroxide with naturally occurring fats. The equation for one such reaction is $\mathrm{C}_{3} \mathrm{H}_{5}\left(\mathrm{C}_{1} \mathrm{H}_{35}\mathrm{COO}\right)_{3}+3 \mathrm{NaOH} \rightarrow \mathrm{C}_{3} \mathrm{H}_{5}(\mathrm{OH})_{3}+$ $3 \mathrm{C}_{17} \mathrm{H}_{35} \mathrm{COONa}$.The last compound is the soap. Calculate the number of grams of sodium hydroxide required to produce 323 grams of soap by this method.

Ronald Prasad

Numerade Educator

Problem 12

According to the reaction $\mathrm{CH}_{4}+\mathrm{CCl}_{4} \rightarrow 2 \mathrm{CH}_{2} \mathrm{Cl}_{2}$,How many grams of carbon tetrachloride are required for the complete reaction of 24.7 grams of methane, $\mathrm{CH}_{4} ?$

Ronald Prasad

Numerade Educator

Problem 13

13. One way to make sodium thiosulfate, known as "hypo" and used in photographic developing, is described by the equation $\mathrm{Na}_{2} \mathrm{CO}_{3}+2 \mathrm{Na}_{2} \mathrm{S}+4 \mathrm{SO}_{2} \rightarrow 3 \mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3}+\mathrm{CO}_{2} .$ How many grams of sodium carbonate are required to produce 681 grams of sodium thiosulfate?

Nicole Smina

Numerade Educator

Problem 14

One of the methods for manufacturing sodium sulfate, once widely used in making the kraft paper for grocery bags, involves the reaction $4 \mathrm{NaCl}+2 \mathrm{SO}_{2}+2 \mathrm{H}_{2} \mathrm{O}+\mathrm{O}_{2} \rightarrow 2 \mathrm{Na}_{2} \mathrm{SO}_{4}+$
4 HCI. Calculate the number of kilograms of sodium chloride required to produce 5.00 kilograms of sodium sulfate.

Ronald Prasad

Numerade Educator

Problem 15

The hard water scum that forms a ring around the bathtub is an insoluble soap, $\mathrm{Ca}\left(\mathrm{C}_{18} \mathrm{H}_{35} \mathrm{O}_{2}\right)_{2}$. It is formed when a soluble soap, $\mathrm{NaC}_{18} \mathrm{H}_{35} \mathrm{O}_{2}$, reacts with the calcium ion that is responsible for the hardness in water: $2 \mathrm{NaC}_{18} \mathrm{H}_{35} \mathrm{O}_{2}+\mathrm{Ca}^{2+} \rightarrow$,$\mathrm{Ca}\left(\mathrm{C}_{18} \mathrm{H}_{35} \mathrm{O}_{2}\right)_{2}+2 \mathrm{Na}^{+} .$ How many milligrams of scum can from 616 milligrams of $\mathrm{NaC}_{18} \mathrm{H}_{35} \mathrm{O}_{2} ?$

Ronald Prasad

Numerade Educator

Problem 16

Trinitrotoluene is the chemical name for the explosive commonly known as TNT. Its formula is $\mathrm{C}_{7} \mathrm{H}_{5} \mathrm{N}_{3} \mathrm{O}_{6}$. TNT is manufactured by the reaction of toluene, $\mathrm{C}_{7} \mathrm{H}_{8},$ with nitric acid:
$\mathrm{C}_{7} \mathrm{H}_{8}+3 \mathrm{HNO}_{3} \rightarrow \mathrm{C}_{7} \mathrm{H}_{5} \mathrm{N}_{3} \mathrm{O}_{6}+3 \mathrm{H}_{2} \mathrm{O}$.a) How much nitric acid is needed to react completely with 1.90 kilograms of toluene?
b) How many kilograms of TNT can be produced in the reaction?

Ronald Prasad

Numerade Educator

Problem 17

Pig iron from a blast furnace contains several impurities, one of which is phosphorus. Additional iron ore, $\mathrm{Fe}_{2} \mathrm{O}_{3},$ is included with pig iron in making steel. The oxygen in the ore oxidizes the phosphorus by the reaction $12 \mathrm{P}+10 \mathrm{Fe}_{2} \mathrm{O}_{3} \rightarrow 3 \mathrm{P}_{4} \mathrm{O}_{10}+20 \mathrm{Fe}$.If a sample of the remains from the furnace contains 802 milligrams of tetraphosphorus decoxide, how many grams of $\mathrm{Fe}_{2} \mathrm{O}_{3}$ was used in making it?

Ronald Prasad

Numerade Educator

Problem 18

According to the reaction $\mathrm{N}_{2}+\mathrm{O}_{2} \rightarrow 2 \mathrm{NO},$ how many grams of nitrogen monoxide will be formed upon the complete reaction of 25.4 grams of oxygen gas with excess nitrogen gas?

Ronald Prasad

Numerade Educator

Problem 19

How much NaCl is needed to react completely with 83.0 grams of ammonium hydrogen carbonate in $\mathrm{NaCl}+\mathrm{NH}_{4} \mathrm{HCO}_{3}$ $\rightarrow \mathrm{NaHCO}_{3}+\mathrm{NH}_{4} \mathrm{Cl} ?$

Ronald Prasad

Numerade Educator

Problem 20

How many grams of ammonium hydrogen carbonate will be formed by the reaction of 81.2 grams of ammonia in the reaction $\mathrm{NH}_{3}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2} \rightarrow \mathrm{NH}_{4} \mathrm{HCO}_{3} ?$

Ronald Prasad

Numerade Educator

Problem 21

By-product ammonia is recovered from the Solvay process by the reaction $\mathrm{Ca}(\mathrm{OH})_{2}+2 \mathrm{NH}_{4} \mathrm{Cl} \rightarrow \mathrm{CaCl}_{2}+2 \mathrm{H}_{2} \mathrm{O}+2 \mathrm{NH}_{3}$.How many grams of calcium chloride can be produced along with 62.0 grams of ammonia?

Ronald Prasad

Numerade Educator

Problem 22

What mass of NaHCO_must decompose to produce 448 grams of $\mathrm{Na}_{2} \mathrm{CO}_{3}$ in $2 \mathrm{NaHCO}_{3} \rightarrow \mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2} ?$

Ronald Prasad

Numerade Educator

Problem 23

How many grams of sodium hydroxide are needed to neutralize completely 32.6 grams of phosphoric acid?

Ronald Prasad

Numerade Educator

Problem 24

Aqueous ammonium chloride decomposes to form ammonia gas and aqueous hydrochloric acid. How many grams of ammonia will be formed upon the complete reaction of 28.3 grams of ammonium chloride?

Ronald Prasad

Numerade Educator

Problem 25

What mass of magnesium hydroxide will precipitate if 2.09 grams of potassium hydroxide is added to a magnesium nitrate solution?

Ronald Prasad

Numerade Educator

Problem 26

Under specialized conditions, an aqueous solution of hydrobromic acid can decompose to hydrogen gas and liquid bromine. How many grams of hydrobromic acid are needed to form 31.5 grams of bromine?

Ronald Prasad

Numerade Educator

Problem 27

An experimenter recovers 0.521 gram of sodium sulfate from the neutralization of sodium hydroxide by sulfuric acid. How many grams of sulfuric acid reacted?

Ronald Prasad

Numerade Educator

Problem 28

Solid sulfur reacts with carbon monoxide gas to form gaseous sulfur dioxide and solid carbon. How many grams of carbon monoxide are required for the complete reaction of 25.5 grams of sulfur?

Ronald Prasad

Numerade Educator

Problem 29

The reaction of a dry-cell battery may be represented as follows: zinc reacts with ammonium chloride to form zinc chloride, ammonia, and hydrogen. Calculate the number of grams of zinc consumed during the release of 7.05 grams of ammonia in such a cell.

Ronald Prasad

Numerade Educator

Problem 30

Solid calcium carbonate decomposes to solid calcium oxide and carbon dioxide gas. How many grams of calcium carbonate are needed to form 22.8 grams of carbon dioxide?

Ronald Prasad

Numerade Educator

Problem 31

The function of "hypo" (see Question 13) in photographic developing is to remove excess silver bromide by the reaction $2 \mathrm{Na}_{2} \mathrm{S}_{2} \mathrm{O}_{3}+\mathrm{AgBr} \rightarrow \mathrm{Na}_{3} \mathrm{Ag}\left(\mathrm{S}_{2} \mathrm{O}_{3}\right)_{2}+\mathrm{NaBr} .$ What is the percent yield if the reaction of 8.18 grams of sodium thiosulfate produces 2.61 grams of sodium bromide?

Ronald Prasad

Numerade Educator

Problem 32

Butane gas is used as a fuel for camp stoves, producing heat in the reaction $2 \mathrm{C}_{4} \mathrm{H}_{10}+13 \mathrm{O}_{2} \rightarrow 8 \mathrm{CO}_{2}+10 \mathrm{H}_{2} \mathrm{O} .$ When 4.14 grams of butane reacts with excess oxygen gas, the reaction yields 11.0 grams of carbon dioxide. What is the percent yield in this reaction?

Ronald Prasad

Numerade Educator

Problem 33

Calcium cyanamide is a common fertilizer. When mixed with water in the soil, it reacts to produce calcium carbonate and ammonia: $\mathrm{CaCN}_{2}+3 \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{CaCO}_{3}+2 \mathrm{NH}_{3} .$ How much ammonia
can be obtained from 7.25 grams of calcium cyanamide in a laboratory experiment in which the percent yield will be $92.8 \% ?$

Ronald Prasad

Numerade Educator

Problem 34

Hydrochloric acid is known as an enemy of stainless steel, the primary component of which is iron. The reaction is $2 \mathrm{HCl}+$ $\mathrm{Fe} \rightarrow \mathrm{FeCl}_{2}+\mathrm{H}_{2}$ What will be the actual yield of iron(II) chloride when 3.17 grams of iron reacts with excess hydrochloric acid? Assume that the percent yield of iron(II) chloride is $76.6 \%$.

Ronald Prasad

Numerade Educator

Problem 35

The Haber process for making ammonia from nitrogen in the air is given by the equation $\mathrm{N}_{2}+3 \mathrm{H}_{2} \rightarrow 2 \mathrm{NH}_{3}$. Calculate the mass of hydrogen that must be supplied to make $5.00 \times 10^{2} \mathrm{kg}$ of ammonia in a system that has an $88.8 \%$ yield.

Ronald Prasad

Numerade Educator

Problem 36

Hydrogen iodide is a colorless, nonflammable, and corrosive gas with a penetrating and suffocating odor. It can be prepared by direct reaction of its elements: $\mathrm{H}_{2}+\mathrm{I}_{2} \rightarrow 2 \mathrm{HI} .$ It is desired to produce 331 grams of hydrogen iodide in a process in which the percent yield is $71.1 \% .$ How many grams of hydrogen gas will need to be reacted?

Ronald Prasad

Numerade Educator

Problem 37

Calculate the percent yield in the photosynthesis reaction by which carbon dioxide is converted to sugar if 7.03 grams of carbon dioxide yields 3.92 grams of $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}$. The equation is $6 \mathrm{CO}_{2}$ $+6 \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+6 \mathrm{O}_{2}$.

Ronald Prasad

Numerade Educator

Problem 38

The simplest example of the hydrogenation of a carbon-carbon double bond is the reaction between ethene and hydrogen in the presence of nickel: $\mathrm{CH}_{2}=\mathrm{CH}_{2}+\mathrm{H}_{2} \stackrel{\mathrm{Ni}}{\longrightarrow} \mathrm{CH}_{3} \mathrm{CH}_{3} .$ When 5.20 grams of ethene reacts with excess hydrogen gas, the reaction yields 4.75 grams of ethane. What is the percent yield for this reaction?

Ronald Prasad

Numerade Educator

Problem 39

Ethylacetate, $\mathrm{CH}_{3} \mathrm{COOC}_{2} \mathrm{H}_{5}$, is manufactured by the reaction between acetic acid, $\mathrm{CH}_{3} \mathrm{COOH},$ and ethanol, $\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}:$
$\mathrm{CH}_{3} \mathrm{COOH}+\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH} \rightarrow \mathrm{CH}_{3} \mathrm{COOC}_{2} \mathrm{H}_{5}+\mathrm{H}_{2} \mathrm{O} .$ How much acetic acid must be used to get 62.5 kilograms of ethylacetate if the percent yield is $69.1 \% ?$

Ronald Prasad

Numerade Educator

Problem 40

Nitrogen monoxide is produced by combustion in an automobile engine. It can then react with oxygen: $2 \mathrm{NO}+\mathrm{O}_{2} \rightarrow$ $2 \mathrm{NO}_{2} .$ If 5.74 grams of oxygen gas reacts with excess nitrogen monoxide in a system in which the percent yield of nitrogen dioxide is $80.2 \%,$ what is the actual yield of nitrogen dioxide?

Ronald Prasad

Numerade Educator

Problem 41

Ammonia can be formed from a combination reaction of its elements. A small fraction of an unreacted mixture of elements is illustrated in the following diagram, where white spheres represent hydrogen atoms and blue spheres represent nitrogen atoms. The temperature is such that all species are gases.a) Write and balance the equation for the reaction. b) Which of the following correctly represents the product mixture?a) Write and balance the equation for the reaction.
b) Which of the following correctly represents the product mixture?
c) Which species is the limiting reactant? Explain.
(IMAGES CAN'T COPY)

Crystal Wang

Numerade Educator

Problem 42

Carbon monoxide reacts with oxygen to form carbon dioxide at a temperature at which all species are in the gas phase. A tiny sample of the pre-reaction mixture is shown in the following diagram, where blue spheres represent oxygen atoms and gold spheres represent carbon atoms. Draw the product mixture. Give a written description of your reasoning.
(FIGURE CANT COPY)

Ronald Prasad

Numerade Educator

Problem 43

An experiment is conducted in which varying amounts of solid iron are added to a fixed volume of liquid bromine. The product of the reaction is a single compound, which can be separated from the product mixture and weighed. The graph shows the relationship between the mass of iron in each trial versus the mass of the product compound. Explain why the graph has a positive slope for low masses of iron and a zero slope when the mass of iron added becomes larger.
(GRAPH CAN'T COPY)

Ronald Prasad

Numerade Educator

Problem 44

The flasks below illustrate three trials of a reaction between varying amounts of zinc and a constant volume of hydrochloric acid solution. The table gives the initial amount of zinc added and the observations at the conclusion of each reaction.
(FIGURES CANT COPY)
(TABLE CAN'T COPY)
The reaction produces an aqueous solution of zinc chloride and hydrogen gas. Explain the observed results.

Ronald Prasad

Numerade Educator

Problem 45

A solution containing 1.63 grams of barium chloride is added to a solution containing 2.40 grams of sodium chromate (chromate ion, $\mathrm{CrO}_{4}^{2-}$ ). Find the number of grams of barium chromate that can precipitate. Also determine which reactant was in excess, as well as the number of grams over the amount required by the limiting reactant.

Ronald Prasad

Numerade Educator

Problem 46

Carbon dioxide can be removed from the air by reaction with potassium hydroxide: $\mathrm{CO}_{2}+2 \mathrm{KOH} \rightarrow \mathrm{K}_{2} \mathrm{CO}_{3}+\mathrm{H}_{2} \mathrm{O} .$ If 15.6 grams of carbon dioxide reacts with 43.0 grams of potassium hydroxide, what mass of potassium carbonate will be formed? What amount of excess reactant remains after the reaction is complete?

Ronald Prasad

Numerade Educator

Problem 47

The equation for one method of preparing iodine is $2 \mathrm{NaIO}_{3}$ $+5 \mathrm{NaHSO}_{3} \rightarrow \mathrm{I}_{2}+3 \mathrm{NaHSO}_{4}+2 \mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O} .$ If 6.00 kilograms of sodium iodate is reacted with 7.33 kilograms of sodium hydrogen sulfite, how many kilograms of iodine can be produced? Which reactant will be left over? How many kilograms will be left?

Ronald Prasad

Numerade Educator

Problem 48

Carbon monoxide is the chief waste product of the gasoline combustion process. Auto manufacturers use catalytic converters to convert carbon monoxide into carbon dioxide:$2 \mathrm{CO}+\mathrm{O}_{2} \rightarrow 2 \mathrm{CO}_{2} .$ When 12.6 grams of carbon monoxide is allowed to react with 5.22 grams of oxygen gas, how many grams of carbon dioxide are formed? What amount of the excess reactant remains after the reaction is complete?

Ronald Prasad

Numerade Educator

Problem 49

A mixture of tetraphosphorus trisulfide and powdered glass is in the white tip of strike-anywhere matches. The $P_{4} S_{3}$ is made by the direct combination of the elements: $8 \mathrm{P}_{4}+3 \mathrm{S}_{8} \rightarrow 8 \mathrm{P}_{4} \mathrm{S}_{3}$. If 133 grams of phosphorus is mixed with the full contents of a $126-$ g (4-oz) bottle of sulfur, how many grams of the compound can be formed? How much of which element will be left over?

Ronald Prasad

Numerade Educator

Problem 50

Sodium carbonate can neutralize nitric acid by the reaction $2 \mathrm{HNO}_{3}+\mathrm{Na}_{2} \mathrm{CO}_{3} \rightarrow 2 \mathrm{NaNO}_{3}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2} .$ Is 135 grams of sodium carbonate enough to neutralize a solution that contains 188 grams of nitric acid? How many grams of carbon dioxide will be released in the reaction?

Ronald Prasad

Numerade Educator

Problem 51

a) How many kilojoules are equal to 0.731 kcal?
b) What number of calories is the same as $651 \mathrm{J} ?$
c) Determine the number of kilocalories that is equivalent to $6.22 \times 10^{3} \mathrm{J}$

Ronald Prasad

Numerade Educator

Problem 52

Complete the following:
a) $504 \mathrm{J}=\quad$ _______________ cal =__________________.kj.
b) 192 cal $=_________________________j=_________________________kJ.
c) $0.423 kj_______________________j=____________________________cal.

Ronald Prasad

Numerade Educator

Problem 53

When $15 \mathrm{g}$ of carbon is burned, $493 \mathrm{kJ}$ of energy is released. Calculate the number of calories and kilocalories this represents.

Ronald Prasad

Numerade Educator

Problem 54

A list of the calorie content of foods indicates that a piece of lemon meringue pie contains 333 Calories. Express this value in $\mathrm{kJ}$ and in $\mathrm{J}$..

Ronald Prasad

Numerade Educator

Problem 55

Each day, $5.8 \times 10^{2}$ kcal of heat is removed from the body by evaporation. How many kilojoules are removed in a year?

Ronald Prasad

Numerade Educator

Problem 56

Burning sucrose releases $3.94 \times 10^{3}$ callg. Calculate the kilojoules released when 56.7 grams of sucrose is burned.

Ronald Prasad

Numerade Educator

Problem 57

Energy is absorbed from sunlight in the photosynthesis reaction in which carbon dioxide and water vapor combine to produce sugar, $\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6},$ and release oxygen. The amount of energy is 2.82 $\times 10^{3} \mathrm{kJ}$ per mole of sugar formed.

Ronald Prasad

Numerade Educator

Problem 58

When gaseous nitrogen reacts with gaseous oxygen to form nitrogen dioxide gas, $66.4 \mathrm{kJ}$ of energy is absorbed for each mole of nitrogen that reacts.

Ronald Prasad

Numerade Educator

Problem 59

The electrolysis of water is an endothermic reaction, absorbing $286 \mathrm{kJ}$ for each mole of liquid water decomposed to its elements.

Ronald Prasad

Numerade Educator

Problem 60

When ammonia and oxygen react at a temperature at which both compounds are in the gaseous state, $226 \mathrm{kJ}$ of energy is evolved for each mole of ammonia that reacts. Gaseous nitrogen monoxide and steam are the products of the reaction.

Ronald Prasad

Numerade Educator

Problem 61

The reaction in an oxyacetylene torch is highly exothermic, releasing $1.31 \times 10^{3} \mathrm{kJ}$ of heat for every mole of acetylene, $\mathrm{C}_{2} \mathrm{H}_{2}(\mathrm{g}),$ burned. The end products are gaseous carbon dioxide and liquid water.

Ronald Prasad

Numerade Educator

Problem 62

Carbon dioxide gas reacts with hydrogen gas to form carbon monoxide gas and steam, and $41.2 \mathrm{kJ}$ of energy is absorbed for each mole of carbon dioxide that reacts.

Ronald Prasad

Numerade Educator

Problem 63

Quicklime, the common name for calcium oxide, $\mathrm{CaO}$, is made by heating limestone, $\mathrm{CaCO}_{3}$, in slowly rotating kilns about $2^{1 / 2}$ meters in diameter and about 60 meters long. The reaction is $\mathrm{CaCO}_{3}(\mathrm{s})+178 \mathrm{kJ} \rightarrow \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{g}) .$ How many kilojoules are required to decompose $5.80 .\mathrm{kg}$ of limestone?

Ronald Prasad

Numerade Educator

Problem 64

How many grams of hydrogen would have to react to produce 71.9 kJ of energy from the reaction 2 $\mathrm{H}_{2}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g}) \rightarrow$ $2 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+484 \mathrm{kJ} ?$

Ronald Prasad

Numerade Educator

Problem 65

The quicklime produced in Question 63 is frequently converted to calcium hydroxide, sometimes called slaked lime, by an exothermic reaction with water: $\mathrm{CaO}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\ell) \rightarrow \mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{s})$
$+65.3 \mathrm{kJ} .$ How many grams of quicklime was processed in a reaction that produced 291 kJ of energy?

Ronald Prasad

Numerade Educator

Problem 66

$\quad \Delta H=-75.8 \mathrm{kJ}$ for the reaction $\mathrm{S}(\mathrm{s})+2 \mathrm{CO}(\mathrm{g}) \rightarrow$,$\mathrm{SO}_{2}(\mathrm{g})+2 \mathrm{C}(\mathrm{s}) .$ When 10.1 grams of sulfur react with excess carbon monoxide, how many kilojoules of energy are evolved or absorbed?

Ronald Prasad

Numerade Educator

Problem 67

How many grams of octane, a component of gasoline, would you have to burn in your car to liberate $9.48 \times 10^{5} \mathrm{kJ}$ of energy? $\Delta \mathrm{H}=-1.09 \times 10^{4} \mathrm{kJ}$ for the reaction $2 \mathrm{C}_{8} \mathrm{H}_{18}(\ell)+25 \mathrm{O}_{2}(\mathrm{g}) \rightarrow$,$16 \mathrm{CO}_{2}(\mathrm{g})+18 \mathrm{H}_{2} \mathrm{O}(\ell)$.

Ronald Prasad

Numerade Educator

Problem 68

Calculate the quantity of energy (kJ) evolved or absorbed when 10.4 grams of carbon dioxide reacts with excess hydrogen if $\Delta \mathrm{H}=41.2 \mathrm{kJ}$ for the reaction $\mathrm{CO}_{2}(\mathrm{g})+\mathrm{H}_{2}(\mathrm{g}) \rightarrow \mathrm{CO}(\mathrm{g})+$,$\mathrm{H}_{2} \mathrm{O}(\mathrm{g})$.

Ronald Prasad

Numerade Educator

Problem 69

Distinguish precisely and in scientific terms the differences among items in each of the following pairs or groups.
a) Theoretical, actual, and percent yield
b) Limiting reactant, excess reactant
c) Heat of reaction, enthalpy of reaction
d) Chemical equation, thermochemical equation
e) Stoichiometry, thermochemical stoichiometry
f) Joule, calorie

Ronald Prasad

Numerade Educator

Problem 70

Classify each of the following statements as true or false:
a) Coefficients in a chemical equation express the molar proportions among both reactants and products.
b) A stoichiometry problem can be solved with an unbalanced equation.
c) In solving a stoichiometry problem, the change from quantity of given substance to quantity of wanted substance is based on masses.
d) Percent yield is actual yield expressed as a percent of theoreti-
cal yield.
e) The quantity of product of any reaction can be calculated only through the moles of the limiting reactant.
f) $\Delta \mathrm{H}$ is positive for an endothermic reaction and negative for an exothermic reaction.

Ronald Prasad

Numerade Educator

Problem 71

One of the few ways of "fixing" nitrogen, that is, making a nitrogen compound from the elemental nitrogen in the atmosphere, is by the reaction $\mathrm{Na}_{2} \mathrm{CO}_{3}+4 \mathrm{C}+\mathrm{N}_{2} \rightarrow 2 \mathrm{NaCN}+$
3 CO. Calculate the mass in grams of $\mathrm{Na}_{2} \mathrm{CO}_{3}$ required to react with $35 \mathrm{g} \mathrm{N}_{2}$

Ronald Prasad

Numerade Educator

Problem 72

How many grams of calcium phosphate will precipitate if excess calcium nitrate is added to a solution containing 3.98 grams of sodium phosphate?

Ronald Prasad

Numerade Educator

Problem 73

Emergency oxygen masks contain potassium superoxide. $\mathrm{KO}_{2},$ pellets. When exhaled $\mathrm{CO}_{2}$ passes through the $\mathrm{KO}_{2},$ the following reaction occurs: $4 \mathrm{KO}_{2}(\mathrm{s})+2 \mathrm{CO}_{2}(\mathrm{g}) \rightarrow 2 \mathrm{K}_{2} \mathrm{CO}_{3}(\mathrm{s})+$,$3 \mathrm{O}_{2}(\mathrm{g}) .$ The oxygen produced can then be inhaled, so no air from outside the mask is needed. If the mask contains 125 grams of $\mathrm{KO}_{2},$ how many grams of oxygen can be produced?

Ronald Prasad

Numerade Educator

Problem 74

Baking cakes and pastries involves the production of $\mathrm{CO}_{2}$ to make the batter rise. For example, citric acid, $\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7},$ in lemon or orange juice can react with baking soda, $\mathrm{NaHCO}_{3},$ to produce carbon dioxide gas: $\mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(\mathrm{aq})+3 \mathrm{NaHCO}_{3}(\mathrm{aq}) \rightarrow$,$\mathrm{Na}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}(\mathrm{aq})+3 \mathrm{CO}_{2}(\mathrm{g})+3 \mathrm{H}_{2} \mathrm{O}(\ell)$.
a) If $6.00 \mathrm{g} \mathrm{H}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}$ reacts with $20.0 \mathrm{g} \mathrm{NaHCO}_{3},$ how many
grams of carbon dioxide will be produced?
b) How many grams of which reactant will remain unreacted?
c) Can you name $\mathrm{Na}_{3} \mathrm{C}_{6} \mathrm{H}_{5} \mathrm{O}_{7}$ ? Remember, it comes from citric acid.

Ronald Prasad

Numerade Educator

Problem 75

A laboratory test of 12.8 grams of aluminum ore yields 1.68 grams of aluminum. If the aluminum compound in the ore is $\mathrm{Al}_{2} \mathrm{O}_{3}$ and it is converted to the pure metal by the reaction $2 \mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{s})+3 \mathrm{C}(\mathrm{s}) \rightarrow 4 \mathrm{Al}(\mathrm{s})+3 \mathrm{CO}_{2}(\mathrm{g}),$ what is the percentage of $\mathrm{Al}_{2} \mathrm{O}_{3}$ in the ore?

Ronald Prasad

Numerade Educator

Problem 76

How much energy is required to decompose 1.42 grams of $\mathrm{KClO}_{3}$ according to the following equation: $2 \mathrm{KClO}_{3}(\mathrm{s}) \rightarrow$ $2 \mathrm{KCl}(\mathrm{s})+3 \mathrm{O}_{2}(\mathrm{g}) ? \Delta \mathrm{H}=89.5 \mathrm{kJ}$ for the reaction.

Ronald Prasad

Numerade Educator

Problem 77

A phosphate rock quarry yields rock that is $79.4 \%$ calcium phosphate, the raw material used in preparing $\mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2},$ a fertilizer known as superphosphate. The rock is made to react with sulfuric acid according to the equation $\mathrm{Ca}_{3}\left(\mathrm{PO}_{4}\right)_{2}+2 \mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow$
$\mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2}+2 \mathrm{CaSO}_{4} .$ What is the smallest number of kilo-
grams of rock that must be processed to yield 0.500 ton of fertilizer?

Ronald Prasad

Numerade Educator

Problem 78

Carborundum, SiC, is widely used as an abrasive in industrial grinding wheels. It is prepared by the reaction of sand, $\mathrm{SiO}_{2}$, with the carbon in coke: $\mathrm{SiO}_{2}+3 \mathrm{C} \rightarrow \mathrm{SiC}+2$ CO. How many kilograms of carborundum can be prepared from 727 kg of coke that is $88.9 \%$ carbon?

Ronald Prasad

Numerade Educator

Problem 79

A sludge containing silver chloride is a waste product from making mirrors. The silver may be recovered by dissolving the silver chloride in a sodium cyanide (NaCN) solution, and then reducing the silver with zinc. The overall equation is $2 \mathrm{AgCl}+$ $4 \mathrm{NaCN}+\mathrm{Zn} \rightarrow 2 \mathrm{NaCl}+\mathrm{Na}_{2} \mathrm{Zn}(\mathrm{CN})_{4}+2 \mathrm{Ag} .$ What minimum amount of sodium cyanide is needed to dissolve all the silver chloride from 40.1 kilograms of sludge that is $23.1 \%$ silver chloride?

Ronald Prasad

Numerade Educator

Problem 80

The chemical equation that describes what happens in an automobile storage battery as it generates electrical energy is $\mathrm{PbO}_{2}+\mathrm{Pb}+2 \mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow 2 \mathrm{PbSO}_{4}+2 \mathrm{H}_{2} \mathrm{O}$
a) What fraction of the lead in $\mathrm{PbSO}_{4}$ comes from $\mathrm{PbO}_{2}$ and what fraction comes from elemental lead?
b) If the operation of the process uses $29.7 \mathrm{g}$ PbSO, how many grams of $\mathrm{PbO}_{2}$ must have been consumed?

Ronald Prasad

Numerade Educator

Problem 81

Hydrogen and chlorine are produced simultaneously in commercial quantities by the electrolysis of salt water: $2 \mathrm{NaCl}+$ $2 \mathrm{H}_{2} \mathrm{O} \rightarrow 2 \mathrm{NaOH}+\mathrm{H}_{2}+\mathrm{Cl}_{2} .$ Yield from the process is $61 \%$
What mass of solution that is $9.6 \%$ NaCl must be processed to obtain 105 kilograms of chlorine?

Ronald Prasad

Numerade Educator

Problem 82

A dry mixture of hydrogen chloride and air is passed over a heated catalyst in the Deacon process for manufacturing chlorine. Oxidation occurs by the following reaction: $4 \mathrm{HCl}+\mathrm{O}_{2} \rightarrow 2 \mathrm{Cl}_{2}$ $+2 \mathrm{H}_{2} \mathrm{O} .$ If the conversion is $63 \%$ complete, how many tons of chlorine can be recovered from 1.4 tons of HCl? (Hint: Whatever you can do with moles, kilomoles, and millimoles, you can also do with ton-moles.)

Ronald Prasad

Numerade Educator

Problem 83

Fluorides retard tooth decay by forming a hard, acid-resisting calcium fluoride layer in the reaction $\mathrm{SnF}_{2}+\mathrm{Ca}(\mathrm{OH})_{2} \rightarrow \mathrm{CaF}_{2}+$,$\mathrm{Sn}(\mathrm{OH})_{2}$. If at the time of a treatment there are $239 \mathrm{mg} \mathrm{Ca}(\mathrm{OH})_{2}$,on the teeth and the dentist uses a mixture that contains $305 \mathrm{mg}$ $\mathrm{SnF}_{2},$ has enough of the mixture been used to convert all of the $\mathrm{Ca}(\mathrm{OH})_{2} ?$ If no, what minimum additional amount should have been used? If yes, by what number of milligrams was the amount in excess?

Ronald Prasad

Numerade Educator

Problem 84

In the recovery of silver from silver chloride waste (see Question 79 ) a certain quantity of waste material is estimated to contain $184 \mathrm{g}$ of silver chloride, $\mathrm{AgCl}$. The treatment tanks are charged with 45 grams of zinc and 145 grams of sodium cyanide, NaCN. Is there enough of the two reactants to recover all of the silver from the AgCl? If no, how many grams of silver chloride will remain? If yes, how many more grams of silver chloride could have been treated by the available Zn and NaCN?

Ronald Prasad

Numerade Educator

Problem 85

In 1866 a young chemistry student conceived the electrolytic method of obtaining aluminum from its oxide. This method is still used. $\Delta \mathrm{H}=1.97 \times 10^{3} \mathrm{kJ}$ for the reaction $2 \mathrm{Al}_{2} \mathrm{O}_{3}(\mathrm{s})+3 \mathrm{C}(\mathrm{s}) \rightarrow$,$4 \mathrm{Al}(\mathrm{s})+3 \mathrm{CO}_{2}(\mathrm{g}) .$ The large amount of electrical energy required limits the process to areas of relatively inexpensive power. How many kilowatt-hours of energy are needed to produce one pound $(454 \mathrm{g})$ of aluminum by this process, if $1 \mathrm{kw}-\mathrm{hr}=$ $3.60 \times 10^{3} \mathrm{kJ} ?$

Ronald Prasad

Numerade Educator

Problem 86

Nitroglycerine is the explosive ingredient in industrial dynamite. Much of its destructive force comes from the sudden creation of large volumes of gaseous products. A great deal of energy is released, too. $\Delta \mathrm{H}=-6.17 \times 10^{3} \mathrm{kJ}$ for the equation $4 \mathrm{C}_{3} \mathrm{H}_{5}\left(\mathrm{NO}_{3}\right)_{3}(\ell) \rightarrow 12 \mathrm{CO}_{2}(\mathrm{g})+10 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})+6 \mathrm{N}_{2}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g})$
Calculate the number of pounds of nitroglycerine that must be used in a blasting operation that requires $5.88 \times 10^{4} \mathrm{kJ}$ of energy.

Ronald Prasad

Numerade Educator

Problem 87

A student was given a 1.6240 -g sample of a mixture of sodium nitrate and sodium chloride and was asked to find the percentage of each compound in the mixture. She dissolved the sample and added a solution that contained an excess of silver nitrate, $\mathrm{AgNO}_{3}$. The silver ion precipitated all of the chloride ion in the mixture as AgCl. It was filtered, dried, and weighed. Its mass was 2.056 g. What was the percentage of each compound in the mixture?

Ronald Prasad

Numerade Educator

Problem 88

A researcher dissolved 1.382 grams of impure copper in nitric acid to produce a solution of $\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2} .$ The solution went through a series of steps in which $\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}$ was changed to $\mathrm{Cu}(\mathrm{OH})_{2},$ then to $\mathrm{CuO},$ and then to a solution of $\mathrm{CuCl}_{2} .$ This was treated with an excess of a soluble phosphate, precipitating all the copper in the original sample as pure $\mathrm{Cu}_{3}\left(\mathrm{PO}_{4}\right)_{2}$. The precipitate was dried and weighed. Its mass was 2.637 g. Find the percent copper in the original sample.

Ronald Prasad

Numerade Educator

Problem 89

How many grams of magnesium nitrate, $\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2}$, must be used to precipitate as magnesium hydroxide all of the hydroxide ion in $50.0 \mathrm{mL} 17.0 \% \mathrm{NaOH}$, the density of which is $1.19 \mathrm{g} / \mathrm{mL} ?$.The precipitation reaction is $2 \mathrm{NaOH}+\mathrm{Mg}\left(\mathrm{NO}_{3}\right)_{2} \rightarrow \mathrm{Mg}(\mathrm{OH})_{2}$,$+2 \mathrm{NaNO}_{3}$.

Ronald Prasad

Numerade Educator

Problem 90

If a solution of silver nitrate, $A g N O_{3}$, is added to a second solution containing a chloride, bromide, or iodide, the silver ion, $\mathrm{Ag}^{+},$ from the first solution will precipitate the halide as silver chloride, silver bromide, or silver iodide. If excess $\mathrm{AgNO}_{3}(\mathrm{aq})$ is added to a mixture of the above halides, it will precipitate them both, or all, as the case may be. A solution contains 0.230 g NaCl and $0.771 \mathrm{g}$ NaBr. What is the smallest quantity of $\mathrm{AgNO}_{3}$ that is required to precipitate both halides completely?

Ronald Prasad

Numerade Educator