🎉 Announcing Numerade's $26M Series A, led by IDG Capital!Read how Numerade will revolutionize STEM Learning ## Chapter 7 ## Chemical Reactions and Chemical Quantities ## Educators     + 22 more educators ### Problem 1 What is the greenhouse effect? Joshua S. Numerade Educator ### Problem 2 Why are scientists concerned about increases in atmospheri carbon dioxide? What is the source of the increase? Nicholas W. Numerade Educator ### Problem 3 What is the difference between a physical change and a chemical change? List some examples of each. Joshua S. Numerade Educator ### Problem 4 What is the difference between a physical property and a chemical property? Nicholas W. Numerade Educator ### Problem 5 What is a balanced chemical equation? Joshua S. Numerade Educator ### Problem 6 Why must chemical equations be balanced? Nicholas W. Numerade Educator ### Problem 7 What is reaction stoichiometry? What is the significance of the coefficients in a balanced chemical equation? Joshua S. Numerade Educator ### Problem 8 In a chemical reaction, what is the limiting reactant? What do we mean when we say a reactant is in excess? Nicholas W. Numerade Educator ### Problem 9 In a chemical reaction, what is the theoretical yield? The percent yield? Joshua S. Numerade Educator ### Problem 10 We typically calculate the percent yield using the actual yield and theoretical yield in units of mass (g or kg). Would the percent yield be different if the actual yield and theoretical yield were in units of amount (moles)? Nicholas W. Numerade Educator ### Problem 11 Where does our society get the majority of its energy? Joshua S. Numerade Educator ### Problem 12 What is a combustion reaction? Why are they important? Give an example. Nicholas W. Numerade Educator ### Problem 13 Write a general equation for the reaction of an alkali metal with: a. a halogen b. water Joshua S. Numerade Educator ### Problem 14 Write a general equation for the reaction of a halogen with: a. a metal b. hydrogen c. another halogen Nicholas W. Numerade Educator ### Problem 15 Classify each change as physical or chemical. a. Natural gas burns in a stove. b. The liquid propane in a gas grill evaporates because the valve was left open. c. The liquid propane in a gas grill burns in a flame. d. A bicycle frame rusts on repeated exposure to air and water. Joshua S. Numerade Educator ### Problem 16 Classify each change as physical or chemical. a. Sugar burns when heated on a skillet. b. Sugar dissolves in water. c. A platinum ring becomes dull because of continued abrasion. d. A silver surface becomes tarnished after exposure to air for a long period of time. Nicholas W. Numerade Educator ### Problem 17 Based on the molecular diagram, classify each change as physical or chemical. Charotte M. Numerade Educator ### Problem 18 Based on the molecular diagram, classify each change as physical or chemical. Nicholas W. Numerade Educator ### Problem 19 Classify each of the listed properties of isopropyl alcohol (also known as rubbing alcohol) as physical or chemical. a. colorless b. flammable c. liquid at room temperature d. density = 0.79 g>mL e. mixes with water Joshua S. Numerade Educator ### Problem 20 Classify each of the listed properties of ozone (a pollutant in the lower atmosphere, but part of a protective shield against UV light in the upper atmosphere) as physical or chemical. a. bluish color b. pungent odor c. very reactive d. decomposes on exposure to ultraviolet light e. gas at room temperature Nicholas W. Numerade Educator ### Problem 21 Classify each property as physical or chemical. a. the tendency of ethyl alcohol to burn b. the shine of silver c. the odor of paint thinner d. the flammability of propane gas Joshua S. Numerade Educator ### Problem 22 Classify each property as physical or chemical. a. the boiling point of ethyl alcohol b. the temperature at which dry ice evaporates c. the tendency of iron to rust d. the color of gold Nicholas W. Numerade Educator ### Problem 23 Sulfuric acid (H2SO4) is a component of acid rain that forms when gaseous sulfur dioxide pollutant reacts with gaseous oxygen and liquid water to form aqueous sulfuric acid. Write a balanced chemical equation for this reaction. (Note: This is a simplified representation of this reaction.) Joshua S. Numerade Educator ### Problem 24 Nitric acid (HNO3) is a component of acid rain that forms when gaseous nitrogen dioxide pollutant reacts with gaseous oxygen and liquid water to form aqueous nitric acid. Write a balanced chemical equation for this reaction. (Note: This is a simplified representation of this reaction.) Nicholas W. Numerade Educator ### Problem 25 In a popular classroom demonstration, solid sodium is added to liquid water and reacts to produce hydrogen gas and aqueous sodium hydroxide. Write a balanced chemical equation for this reaction. Joshua S. Numerade Educator ### Problem 26 When iron rusts, solid iron reacts with gaseous oxygen to form solid iron(III) oxide. Write a balanced chemical equation for this reaction. Nicholas W. Numerade Educator ### Problem 27 Write a balanced chemical equation for the fermentation of sucrose (C12H22O11) by yeasts in which the aqueous sugar reacts with liquid water to form aqueous ethyl alcohol (C2H5OH) and carbon dioxide gas. Joshua S. Numerade Educator ### Problem 28 Write a balanced equation for the photosynthesis reaction in which gaseous carbon dioxide and liquid water react in the presence of chlorophyll to produce aqueous glucose (C6H12O6) and oxygen gas. Nicholas W. Numerade Educator ### Problem 29 Write a balanced chemical equation for each reaction. a. Solid lead(II) sulfide reacts with aqueous hydrobromic acid (HBr) to form solid lead(II) bromide and dihydrogen monosulfide gas. b. Gaseous carbon monoxide reacts with hydrogen gas to form gaseous methane (CH4) and liquid water. c. Aqueous hydrochloric acid (HCl) reacts with solid manganese(IV) oxide to form aqueous manganese(II) chloride, liquid water, and chlorine gas. d. Liquid pentane (C5H12) reacts with gaseous oxygen to form gaseous carbon dioxide and liquid water. David C. Numerade Educator ### Problem 30 Write a balanced chemical equation for each reaction. a. Solid copper reacts with solid sulfur to form solid copper(I) sulfide. b. Solid iron(III) oxide reacts with hydrogen gas to form solid iron and liquid water. c. Sulfur dioxide gas reacts with oxygen gas to form sulfur trioxide gas. d. Gaseous ammonia (NH3) reacts with gaseous oxygen to form gaseous nitrogen monoxide and gaseous water. Charotte M. Numerade Educator ### Problem 31 Write a balanced chemical equation for the reaction of aqueous sodium carbonate with aqueous copper(II) chloride to form solid copper(II) carbonate and aqueous sodium chloride. Joshua S. Numerade Educator ### Problem 32 Write a balanced chemical equation for the reaction of aqueous potassium hydroxide with aqueous iron(III) chloride to form solid iron(III) hydroxide and aqueous potassium chloride. Nicholas W. Numerade Educator ### Problem 33 Balance each chemical equation. a. CO2(g) + CaSiO3(s) + H2O(l)-SiO2(s) + Ca(HCO3)2(aq) b. Co(NO3)3(aq) + (NH4)2S(aq)-Co2S3(s) + NH4NO3(aq) c. Cu2O(s) + C(s)-Cu(s) + CO(g) d. H2(g) + Cl2(g)-HCl(g) Joshua S. Numerade Educator ### Problem 34 Balance each chemical equation. a. Na2S(aq) + Cu(NO3)2(aq)-NaNO3(aq) + CuS(s) b. N2H4(l)-NH3(g) + N2(g) c. HCl(aq) + O2(g)-H2O(l) + Cl2(g) d. FeS(s) + HCl(aq)-FeCl2(aq) + H2S(g) Charotte M. Numerade Educator ### Problem 35 Consider the unbalanced equation for the combustion of hexane: C6H14(g) + O2(g)-CO2(g) + H2O(g) Balance the equation and determine how many moles of O2 are required to react completely with 7.2 moles C6H14. Joshua S. Numerade Educator ### Problem 36 Consider the unbalanced equation for the neutralization of acetic acid: HC2H3O2(aq) + Ba(OH)2(aq)-H2O(l ) + Ba(C2H3O2)2(aq) Balance the equation and determine how many moles of Ba(OH)2 are required to completely neutralize 0.461 mole of HC2H3O2. Nicholas W. Numerade Educator ### Problem 37 Calculate how many moles of NO2 form when each quantity of reactant completely reacts. 2 N2O5(g)-4 NO2(g) + O2(g) a. 2.5 mol N2O5 b. 6.8 mol N2O5 c. 15.2 g N2O5 d. 2.87 kg N2O5 David C. Numerade Educator ### Problem 38 Calculate how many moles of NH3 form when each quantity of reactant completely reacts. 3 N2H4(l)-4 NH3(g) + N2(g) a. 2.6 mol N2H4 b. 3.55 mol N2H4 c. 65.3 g N2H4 d. 4.88 kg N2H4 David C. Numerade Educator ### Problem 39 Consider the balanced equation: SiO2(s) + 3 C(s)-SiC(s) + 2 CO(g) Complete the following table showing the appropriate number of moles of reactants and products. If the number of moles of a reactant is provided, fill in the required amount of the other reactant, as well as the moles of each product that forms. If the number of moles of a product is provided, fill in the required amount of each reactant to make that amount of product, as well as the amount of the other product that is made. Patrick B. Numerade Educator ### Problem 40 Consider the balanced equation: 2 N2H4(g) + N2O4(g)-3 N2(g) + 4 H2O(g) Complete the following table showing the appropriate number of moles of reactants and products. If the number of moles of a reactant is provided, fill in the required amount of the other reactant, as well as the moles of each product that forms. If the number of moles of a product is provided, fill in the required amount of each reactant to make that amount of product, as well as the amount of the other product that is made. Nicholas W. Numerade Educator ### Problem 41 Hydrobromic acid (HBr) dissolves solid iron according to the reaction: Fe(s) + 2 HBr(aq)-FeBr2(aq) + H2(g) What mass of HBr (in g) do you need to dissolve a 3.2-g pure iron bar on a padlock? What mass of H2 can the complete reaction of the iron bar produce? Arron M. Numerade Educator ### Problem 42 Sulfuric acid (H2SO4) dissolves aluminum metal according to the reaction: 2 Al(s) + 3 H2SO4(aq)-Al2(SO4)3(aq) + 3 H2(g) Suppose you want to dissolve an aluminum block with a mass of 15.2 g. What minimum mass of H2SO4 (in g) do you need? What mass of H2 gas (in g) can the complete reaction of the aluminum block produce? Charotte M. Numerade Educator ### Problem 43 For each of the reactions, calculate the mass (in grams) of the product that forms when 3.67 g of the underlined reactant completely reacts. Assume that there is more than enough of the other reactant. a. Ba(s) + Cl2(g)-BaCl2(s) b. CaO(s) + CO2(g)-CaCO3(s) c. 2 Mg(s) + O2(g)-2 MgO(s) d. 4 Al(s) + 3 O2(g)-2 Al2O3(s) Arron M. Numerade Educator ### Problem 44 For each of the reactions, calculate the mass (in grams) of the product that forms when 15.39 g of the underlined reactant completely reacts. Assume that there is more than enough of the other reactant. a. 2 K(s) + Cl2(g)-2 KCl(s) b. 2 K(s) + Br2(l)-2 KBr(s) c. 4 Cr(s) + 3 O2(g)-2 Cr2O3(s) d. 2 Sr(s) + O2(g)-2 SrO(s) Nicholas W. Numerade Educator ### Problem 45 For the following reaction, determine the limiting reactant for each of the initial amounts of reactants. 2 Na(s) + Br2(g)-2 NaBr(s) a. 2 mol Na, 2 mol Br2 b. 1.8 mol Na, 1.4 mol Br2 c. 2.5 mol Na, 1 mol Br2 d. 12.6 mol Na, 6.9 mol Br2 Charotte M. Numerade Educator ### Problem 46 Find the limiting reactant for each initial amount of reactants. 4 Al(s) + 3 O2(g)-2 Al2O3(s) a. 1 mol Al, 1 mol O2 b. 4 mol Al, 2.6 mol O2 c. 16 mol Al, 13 mol O2 d. 7.4 mol Al, 6.5 mol O2 Nicholas W. Numerade Educator ### Problem 47 Consider the reaction: 4 HCl(g) + O2(g)-2 H2O(g) + 2 Cl2(g) Each molecular diagram represents an initial mixture of the reactants. How many molecules of Cl2 would form from the reaction mixture that produces the greatest amount of products? David C. Numerade Educator ### Problem 48 Consider the reaction:$2\space \mathrm{CH3OH}(g)+ 3\space \mathrm{O2}(g)-2 \space \mathrm{CO2}(g) + 4\space \mathrm {H2O}(g)$Each of the molecular diagrams represents an initial mixture of the reactants. How many$\mathrm{CO2}$molecules would form from the reaction mixture that produces the greatest amount of products? Nicholas W. Numerade Educator ### Problem 49 Calculate the theoretical yield of the product (in moles) for each initial amount of reactants. Ti(s) + 2 Cl2(g)-TiCl4(s) a. 4 mol Ti, 4 mol Cl2 b. 7 mol Ti, 17 mol Cl2 c. 12.4 mol Ti, 18.8 mol Cl2 Arron M. Numerade Educator ### Problem 50 Calculate the theoretical yield of product (in moles) for each initial amount of reactants. 2 Mn(s) + 2 O2(g)-2 MnO2(s) a. 3 mol Mn, 3 mol O2 b. 4 mol Mn, 7 mol O2 c. 27.5 mol Mn, 43.8 mol O2 Nicholas W. Numerade Educator ### Problem 51 Zinc sulfide reacts with oxygen according to the reaction: 2 ZnS(s) + 3 O2(g)-2 ZnO(s) + 2 SO2(g) A reaction mixture initially contains 4.2 mol ZnS and 6.8 mol O2. Once the reaction has occurred as completely as possible, what amount (in moles) of the excess reactant remains? Arron M. Numerade Educator ### Problem 52 Iron(II) sulfide reacts with hydrochloric acid according to the reaction: FeS(s) + 2 HCl(aq)-FeCl2(s) + H2S(g) A reaction mixture initially contains 0.223 mol FeS and 0.652 mol HCl. Once the reaction has occurred as completely as possible, what amount (in moles) of the excess reactant is left? Nicholas W. Numerade Educator ### Problem 53 For the reaction shown, calculate the theoretical yield of product (in grams) for each initial amount of reactants. 2 Al(s) + 3 Cl2(g)-2 AlCl3(s) a. 2.0 g Al, 2.0 g Cl2 b. 7.5 g Al, 24.8 g Cl2 c. 0.235 g Al, 1.15 g Cl2 Arron M. Numerade Educator ### Problem 54 For the reaction shown, calculate the theoretical yield of the product (in grams) for each initial amount of reactants. Ti(s) + 2 F2(g)-TiF4(s) a. 5.0 g Ti, 5.0 g F2 b. 2.4 g Ti, 1.6 g F2 c. 0.233 g Ti, 0.288 g F2 Nicholas W. Numerade Educator ### Problem 55 Iron(III) oxide reacts with carbon monoxide according to the equation: Fe2O3(s) + 3 CO(g)-2 Fe(s) + 3 CO2(g) A reaction mixture initially contains 22.55 g Fe2O3 and 14.78 g CO. Once the reaction has occurred as completely as possible, what mass (in g) of the excess reactant remains? David C. Numerade Educator ### Problem 56 Elemental phosphorus reacts with chlorine gas according to the equation: P4(s) + 6 Cl2(g)-4 PCl3(l) A reaction mixture initially contains 45.69 g P4 and 131.3 g Cl2. Once the reaction has occurred as completely as possible, what mass (in g) of the excess reactant remains? Nicholas W. Numerade Educator ### Problem 57 Lead(II) ions can be removed from solution with KCl according to the reaction: Pb2+(aq) + 2 KCl(aq)-PbCl2(s) + 2 K+(aq) When 28.5 g KCl is added to a solution containing 25.7 g Pb2+, a PbCl2(s) forms. The solid is filtered and dried and found to have a mass of 29.4 g. Determine the limiting reactant, theoretical yield of PbCl2, and percent yield for the reaction. Arron M. Numerade Educator ### Problem 58 Magnesium oxide can be made by heating magnesium metal in the presence of oxygen. The balanced equation for the reaction is: 2 Mg(s) + O2(g)-2 MgO(s) When 10.1 g of Mg reacts with 10.5 g O2, 11.9 g MgO forms. Determine the limiting reactant, theoretical yield, and percent yield for the reaction. Nicholas W. Numerade Educator ### Problem 59 Urea (CH4N2O) is a common fertilizer that is synthesized by the reaction of ammonia (NH3) with carbon dioxide: 2 NH3(aq) + CO2(aq)-CH4N2O(aq) + H2O(l) In an industrial synthesis of urea, a chemist combines 136.4 kg of ammonia with 211.4 kg of carbon dioxide and obtains 168.4 kg of urea. Determine the limiting reactant, theoretical yield of urea, and percent yield for the reaction. Arron M. Numerade Educator ### Problem 60 Many computer chips are manufactured from silicon, which occurs in nature as SiO2. When SiO2 is heated to melting, it reacts with solid carbon to form liquid silicon and carbon monoxide gas. In an industrial preparation of silicon, 155.8 kg of SiO2 reacts with 78.3 kg of carbon to produce 66.1 kg of silicon. Determine the limiting reactant, theoretical yield, and percent yield for the reaction. Nicholas W. Numerade Educator ### Problem 61 Complete and balance each combustion reaction equation. a. S(s) + O2(g) b. C3H6(g) + O2(g) c. Ca(s) + O2(g) d. C5H12S(l) + O2(g) Arron M. Numerade Educator ### Problem 62 Complete and balance each combustion reaction equation: a. C4H6(g) + O2(g) b. C(s) + O2(g) c. CS2(s) + O2(g) d. C3H8O(l) + O2(g) Nicholas W. Numerade Educator ### Problem 63 Write a balanced chemical equation for the reaction of solid strontium with iodine gas. Ronald P. Numerade Educator ### Problem 64 Based on the ionization energies of the alkali metals (see Section 3.7), which alkali metal would you expect to undergo the most exothermic reaction with chlorine gas? Write a balanced chemical equation for the reaction. Nicholas W. Numerade Educator ### Problem 65 Write a balanced chemical equation for the reaction of solid lithium with liquid water. Arron M. Numerade Educator ### Problem 66 Write a balanced chemical equation for the reaction of solid potassium with liquid water. Nicholas W. Numerade Educator ### Problem 67 Write a balanced equation for the reaction of hydrogen gas with bromine gas. Arron M. Numerade Educator ### Problem 68 Write a balanced equation for the reaction of chlorine gas with fluorine gas. Nicholas W. Numerade Educator ### Problem 69 The combustion of gasoline produces carbon dioxide and water. Assume gasoline to be pure octane (C8H18) and calculate the mass (in kg) of carbon dioxide that is added to the atmosphere per 1.0 kg of octane burned. (Hint: Begin by writing a balanced equation for the combustion reaction.) Arron M. Numerade Educator ### Problem 70 Many home barbeques are fueled with propane gas (C3H8). What mass of carbon dioxide (in kg) forms upon the complete combustion of 18.9 L of propane (approximate contents of one 5-gallon tank)? Assume that the density of the liquid propane in the tank is 0.621 g>mL. (Hint: Begin by writing a balanced equation for the combustion reaction.) David C. Numerade Educator ### Problem 71 Aspirin can be made in the laboratory by reacting acetic anhydride (C4H6O3) with salicylic acid (C7H6O3) to form aspirin (C9H8O4) and acetic acid (C2H4O2). The balanced equation is: C4H6O3 + C7H6O3-C9H8O4 + C2H4O2 In a laboratory synthesis, a student begins with 3.00 mL of acetic anhydride (density = 1.08 g>mL) and 1.25 g of salicylic acid. Once the reaction is complete, the student collects 1.22 g of aspirin. Determine the limiting reactant, theoretical yield of aspirin, and percent yield for the reaction. David C. Numerade Educator ### Problem 72 The combustion of liquid ethanol (C2H5OH) produces carbon dioxide and water. After 4.62 mL of ethanol (density = 0.789 g>mL) burns in the presence of 15.55 g of oxygen gas, 3.72 mL of water (density = 1.00 g>mL) is collected. Determine the limiting reactant, theoretical yield of H2O, and percent yield for the reaction. (Hint: Write a balanced equation for the combustion of ethanol.) Charotte M. Numerade Educator ### Problem 73 A loud classroom demonstration involves igniting a hydrogen-filled balloon. The hydrogen within the balloon reacts explosively with oxygen in the air to form water. If the balloon is filled with a mixture of hydrogen and oxygen, the explosion is even louder than if the balloon is filled only with hydrogen-the intensity of the explosion depends on the relative amounts of oxygen and hydrogen within the balloon. Look at the molecular views representing different amounts of hydrogen and oxygen in four different balloons. Based on the balanced chemical equation, which balloon will make the loudest explosion? (Hint: Write a balanced equation for the chemical reaction first.) Arron M. Numerade Educator ### Problem 74 The nitrogen in sodium nitrate and in ammonium sulfate is available to plants as fertilizer. Which is the more economical source of nitrogen, a fertilizer containing 30.0% sodium nitrate by weight and costing$9.00 per 100 lb or one containing 20.0% ammonium sulfate by weight and costing \$8.10 per 100 lb? Nicholas W.

### Problem 75

The reaction of NH3 and O2 forms NO and water. The NO can be used to convert P4 to P4O6, forming N2 in the process. The P4O6 can be treated with water to form H3PO3, which forms PH3 and H3PO4 when heated. Find the mass of PH3 that forms from the reaction of 1.00 g NH3.

JW
Jennifer W.

### Problem 76

An important reaction that takes place in a blast furnace during the production of iron is the formation of iron metal and CO2 from Fe2O3 and CO. Determine the mass of Fe2O3 required to form 910 kgof iron. Determine the amount of CO2 that forms in this process. Nicholas W.

### Problem 77

A liquid fuel mixture contains 30.35% hexane (C6H14) and 15.85% heptane (C7H16). The remainder is octane (C8H18). What maximum mass of carbon dioxide is produced by the complete combustion of 10.0 kg of this fuel mixture? Arron M.

### Problem 78

Titanium occurs in the magnetic mineral ilmenite (FeTiO3), which is often found mixed with sand. The ilmenite can be separated from the sand with magnets. The titanium can then be extracted from the ilmenite by the following set of reactions:

Suppose that an ilmenite-sand mixture contains 22.8% ilmenite by mass and that the first reaction is carried out with a 90.8% yield. If the second reaction is carried out with an 85.9% yield, what mass of titanium can we obtain from 1.00 kg of the ilmenite-sand mixture? Nicholas W.

### Problem 79

A mixture of C3H8 and C2H2 has a mass of 2.0 g. It is burned in excess O2 to form a mixture of water and carbon dioxide that contains 1.5 times as many moles of CO2 as of water. Find the mass of C2H2 in the original mixture. David C.

### Problem 80

A mixture of 20.6 g of P and 79.4 g Cl2 reacts completely to form PCl3 and PCl5, which are the only products. Determine the mass of PCl3 that forms. Charotte M.

### Problem 81

Lead poisoning is a serious condition resulting from the ingestion of lead in food, water, or other environmental sources. It affects the central nervous system, leading to a variety of symptoms such as distractibility, lethargy, and loss of motor coordination. Lead poisoning is treated with chelating agents, substances that bind to metal ions, allowing them to be eliminated in the urine. A modern chelating agent used for this purpose is succimer (C4H6O4S2). Suppose you are trying to determine the appropriate dose for succimer treatment of lead poisoning. What minimum mass of succimer (in ug) is needed to bind all of the lead in a patient's bloodstream? Assume that patient blood lead levels are 45 ug/dL, that total blood volume is 5.0 L, and that one mole of succimer binds one mole of lead. Arron M.

### Problem 82

A particular kind of emergency breathing apparatus-often placed in mines, caves, or other places where oxygen might become depleted or where the air might become poisoned-works via the following chemical reaction:

Notice that the reaction produces O2, which can be breathed, and absorbs CO2, a product of respiration. Suppose you work for a company interested in producing a self-rescue breathing apparatus (based on the above reaction) that would allow the user to survive for 10 minutes in an emergency situation. What are the important chemical considerations in designing such a unit? Estimate how much KO2 would be required for the apparatus. (Find any necessary additional information-such as human breathing rates-from appropriate sources. Assume that normal air is 20% oxygen.) Nicholas W.

### Problem 83

Metallic aluminum reacts with MnO2 at elevated temperatures to form manganese metal and aluminum oxide. A mixture of the two reactants is 67.2% mole percent Al. Determine the theoretical yield (in grams) of manganese from the reaction of 250 g of this mixture. David C.

### Problem 84

Hydrolysis of the compound B5H9 forms boric acid, H3BO3. Fusion of boric acid with sodium oxide forms a borate salt, Na2B4O7. Without writing complete equations, find the mass (in grams) of B5H9 required to form 151 g of the borate salt by this reaction sequence. Nicholas W.

### Problem 85

Consider the reaction:
4 K(s) + O2(g)-2 K2O(s)

The molar mass of K is 39.09 g>mol and that of O2 is 32.00 g>mol. Without doing any calculations, choose the conditions under which potassium is the limiting reactant and explain your reasoning.
a. 170 g K, 31 g O2
b. 16 g K, 2.5 g O2
c. 165 kg K, 28 kg O2
d. 1.5 g K, 0.38 g O2 Arron M.

### Problem 86

Consider the reaction:
2 NO(g) + 5 H2(g)-2 NH3(g) + 2 H2O(g)

A reaction mixture initially contains 5 moles of NO and 10 moles of H2. Without doing any calculations, determine which set of amounts best represents the mixture after the reactants have reacted as completely as possible. Explain your reasoning.
a. 1 mol NO, 0 mol H2, 4 mol NH3, 4 mol H2O
b. 0 mol NO, 1 mol H2, 5 mol NH3, 5 mol H2O
c. 3 mol NO, 5 mol H2, 2 mol NH3, 2 mol H2O
d. 0 mol NO, 0 mol H2, 4 mol NH3, 4 mol H2O Nicholas W.

### Problem 88

Octane (C8H8), a component of gasoline, reacts with oxygen to form carbon dioxide and water. Write the balanced chemical reaction for this process by passing a single piece of paper around your group and asking each group member to complete the next logical step. As you each complete your step, explain your reasoning to the group. Nicholas W.

### Problem 89

Imagine you mix 16.05 g of methane (CH4) gas and 96.00 g of oxygen (O2) gas and then ignite the mixture. After a bright flash and a loud bang, some water droplets form on the inside of the
reaction vessel.
a. Write the balanced chemical reaction for the combustion of methane.
b. Sketch the process that occurred in the vessel using circles to represent atoms. Represent carbon with black circles, hydrogen with white circles, and oxygen with red circles. Let one circle (or one molecule made of circles bonded together) represent exactly one mole.
c. How many moles of water can you make? How many moles of carbon dioxide?
d. Will anything be left over? What? How much?
e. Identify the following: limiting reactant, reactant in excess, and theoretical yield. Arron M.

### Problem 90

A chemical reaction in which reactants A and B form the product C is studied in the laboratory. The researcher carries out the reaction with differing relative amounts of reactants and measures the amount of product produced. Examine the given tabulated data from the experiment and answer the questions.
a. For which experiments is A the limiting reactant?
b. For which experiments is B the limiting reactant?
c. The molar mass of A is 50.0 g>mol, and the molar mass of B is 75.0 g>mol. What are the coefficients of A and B in the balanced chemical equation?
d. For each of the experiments in which A is the limiting reactant, calculate the mass of B remaining after the reaction has gone to completion. Use the molar masses and coefficients from part c.
e. The molar mass of C is 88.0 g>mol. What is the coefficient of
C in the balanced chemical equation?
f. Calculate an average percent yield for the reaction. Nicholas W.