Question 1

In a blast furnace, elemental iron is produced from a mixture of coke (C), iron ore (Fe3O4), and other reactants. An important reaction sequence is 2C(s) + O2(g) → 2CO(g)
Fe3O4(s) + 4CO(g) → 3Fe(l) + 4CO2(g)
How many moles of iron can be formed in this sequence when 1.00 mol of carbon, as coke, is consumed?

Accepted Answer

A) 6.00 mol Fe 
B) 3.00 mol Fe 
C) 1.33 mol Fe 
D) 1.25 mol Fe 
E) 0.750 mol Fe

Question 2

In combustion analysis, the carbon and hydrogen contents of a substance are determined from the CO2 and H2O, respectively, which are collected in the absorbers.

Accepted Answer

A) True 
 B)False

Question 3

The formula CH3O0.5 is an example of an empirical formula.

Accepted Answer

A) True 
 B)False

Question 4

Balance the following equation for the combustion of benzene: C6H6(l) + O2(g) → H2O(g) + CO2(g)

Accepted Answer

A) C 6H 6( l)+ 9O 2( g)→ 3H 2O( g)+ 6CO 2( g) 
B) C 6H 6( l)+ 9O 2( g)→ 6H 2O( g)+ 6CO 2( g) 
C) 2C 6H 6(l)+ 15O 2(g)→ 6H 2O(g)+ 12CO 2( g) 
D) C 6H 6( l)+ 15O 2( g)→ 3H 2O( g)+ 6CO 2( g) 
E) 2C 6H 6( l)+ 9O 2( g)→ 6H 2O( g)+ 12CO 2( g)

Question 5

Constitutional (structural) isomers have the same molecular formula but different structural formulas.

Accepted Answer

A) True 
 B)False

Question 6

Lead (II) nitrate is a poisonous substance which has been used in the manufacture of special explosives and as a sensitizer in photography. Calculate the mass of lead in 139 g of Pb(NO3)2.

Accepted Answer

A) 107 g 
B) 90.8 g 
C) 87.0 g 
D) 83.4 g 
E) 62.6 g

Question 7

Methanol (CH4O) is converted to bromomethane (CH3Br) as follows: CH4O + HBr → CH3Br + H2O
If 12.23 g of bromomethane are produced when 5.00 g of methanol is reacted with excess HBr, what is the percentage yield?

Accepted Answer

A) 40.9% 
B) 82.6% 
C) 100% 
D) 121% 
E) 245%

Question 8

Phosphorus pentachloride, PCl5, a white solid that has a pungent, unpleasant odor, is used as a catalyst for certain organic reactions. Calculate the number of moles in 38.7 g of PCl5.

Accepted Answer

A) 5.38 mol 
B) 3.55 mol 
C) 0.583 mol 
D) 0.282 mol 
E) 0.186 mol

Question 9

Hydroxylamine nitrate contains 29.17 mass % N, 4.20 mass % H, and 66.63 mass % O. Determine its empirical formula.

Accepted Answer

A) HNO 
B) H 2NO 2 
C) HN 6O 16 
D) HN 16O 7 
E) H 2NO 3

Question 10

In a correctly balanced equation, the number of reactant molecules must equal the number of product molecules.
A)118.15 g/mol
B)99.15 g/mol
C)78.07 g/mol
D)59.08 g/mol
E)50.01 g/mol

Accepted Answer

A) True 
 B)False

Question 11

Potassium chloride is used as a substitute for sodium chloride for individuals with high blood pressure. Identify the limiting reactant and determine the mass of the excess reactant remaining when 7.00 g of chlorine gas reacts with 5.00 g of potassium to form potassium chloride.

Accepted Answer

A) Potassium is the limiting reactant; 2.47 g of chlorine remain. 
B) Potassium is the limiting reactant; 7.23 g of chlorine remain. 
C) Chlorine is the limiting reactant; 4.64 g of potassium remain. 
D) Chlorine is the limiting reactant; 2.70 g of potassium remain. 
E) No limiting reagent: the reactants are present in the correct stoichiometric ratio.

Question 12

Potassium chlorate (used in fireworks, flares, and safety matches) forms oxygen and potassium chloride when heated. KClO3(s) → KCl(s) + O2(g) [unbalanced]
How many grams of oxygen are formed when 26.4 g of potassium chlorate is heated?

Accepted Answer

A) 223 g 
B) 99.1 g 
C) 10.3 g 
D) 6.86 g 
E) 4.60 g

Question 13

Balance the following equation: C8H18O3(l) + O2(g) → H2O(g) + CO2(g)

Accepted Answer

A) C 8H 18O 3( l)+ 8O 2( g)→ 9H 2O( g)+ 8CO 2( g) 
B) C 8H 18O 3( l)+ 11O 2( g)→ 9H 2O( g)+ 8CO 2( g) 
C) 2C 8H 18O 3( l)+ 22O 2( g)→ 9H 2O( g)+ 16CO 2( g) 
D) C 8H 18O 3( l)+ 13O 2( g)→ 18H 2O( g)+ 8CO 2( g) 
E) 2C 8H 18O 3( l)+ 17O 2( g)→ 18H 2O( g)+ 16CO 2( g)

Question 14

A compound containing chromium and silicon contains 73.52 mass percent chromium. Determine its empirical formula.

Accepted Answer

A) CrSi 3 
B) Cr 2Si 3 
C) Cr 3Si 
D) Cr 3Si 2 
E) Cr 2S

Question 15

Gadolinium oxide, a colorless powder which absorbs carbon dioxide from the air, contains 86.76 mass % Gd. Determine its empirical formula.

Accepted Answer

A) Gd 2O 3 
B) Gd 3O 2 
C) Gd 3O 4 
D) Gd 4O 3 
E) GdO

Question 16

Constitutional (structural) isomers have the same empirical formula but different molecular formulas.

Accepted Answer

A) True 
 B)False

Question 17

A compound of bromine and fluorine is used to make UF6, which is an important chemical in processing and reprocessing of nuclear fuel. The compound contains 58.37 mass percent bromine. Determine its empirical formula.

Accepted Answer

A) BrF 
B) BrF 2 
C) Br 2F 3 
D) Br 3F 
E) BrF 3

Question 18

One mole of methane (CH4) contains a total of 3 × 1024 atoms.

Accepted Answer

A) True 
 B)False

Question 19

Household sugar, sucrose, has the molecular formula C12H22O11. What is the percent of carbon in sucrose, by mass?

Accepted Answer

A) 26.7% 
B) 33.3% 
C) 41.4% 
D) 42.1% 
E) 52.8%

Question 20

Lead(II) sulfide was once used in glazing earthenware. It will also react with hydrogen peroxide to form lead(II) sulfate and water. How many grams of hydrogen peroxide are needed to react completely with 265 g of lead(II) sulfide?

Accepted Answer

A) 151 g 
B) 123 g 
C) 50.3 g 
D) 37.7 g 
E) 9.41 g

Exam 3: Stoichiometry of Formulas and Equations

In combustion analysis, the carbon and hydrogen contents of a substance are determined from the CO₂ and H₂O, respectively, which are collected in the absorbers.

The formula CH₃O_0.5 is an example of an empirical formula.

Balance the following equation for the combustion of benzene: C₆H₆(l) + O₂(g) → H₂O(g) + CO₂(g)

Constitutional (structural) isomers have the same molecular formula but different structural formulas.

Lead (II) nitrate is a poisonous substance which has been used in the manufacture of special explosives and as a sensitizer in photography. Calculate the mass of lead in 139 g of Pb(NO₃) ₂.

Methanol (CH₄O) is converted to bromomethane (CH₃Br) as follows: CH₄O + HBr → CH₃Br + H₂O If 12.23 g of bromomethane are produced when 5.00 g of methanol is reacted with excess HBr, what is the percentage yield?

Phosphorus pentachloride, PCl₅, a white solid that has a pungent, unpleasant odor, is used as a catalyst for certain organic reactions. Calculate the number of moles in 38.7 g of PCl₅.

Hydroxylamine nitrate contains 29.17 mass % N, 4.20 mass % H, and 66.63 mass % O. Determine its empirical formula.

In a correctly balanced equation, the number of reactant molecules must equal the number of product molecules. A)118.15 g/mol B)99.15 g/mol C)78.07 g/mol D)59.08 g/mol E)50.01 g/mol

Potassium chloride is used as a substitute for sodium chloride for individuals with high blood pressure. Identify the limiting reactant and determine the mass of the excess reactant remaining when 7.00 g of chlorine gas reacts with 5.00 g of potassium to form potassium chloride.

Potassium chlorate (used in fireworks, flares, and safety matches) forms oxygen and potassium chloride when heated. KClO₃(s) → KCl(s) + O₂(g) [unbalanced] How many grams of oxygen are formed when 26.4 g of potassium chlorate is heated?

Balance the following equation: C₈H₁₈O₃(l) + O₂(g) → H₂O(g) + CO₂(g)

A compound containing chromium and silicon contains 73.52 mass percent chromium. Determine its empirical formula.

Gadolinium oxide, a colorless powder which absorbs carbon dioxide from the air, contains 86.76 mass % Gd. Determine its empirical formula.

Constitutional (structural) isomers have the same empirical formula but different molecular formulas.

A compound of bromine and fluorine is used to make UF₆, which is an important chemical in processing and reprocessing of nuclear fuel. The compound contains 58.37 mass percent bromine. Determine its empirical formula.

One mole of methane (CH₄) contains a total of 3 × 10²⁴ atoms.

Household sugar, sucrose, has the molecular formula C₁₂H₂₂O₁₁. What is the percent of carbon in sucrose, by mass?

Lead(II) sulfide was once used in glazing earthenware. It will also react with hydrogen peroxide to form lead(II) sulfate and water. How many grams of hydrogen peroxide are needed to react completely with 265 g of lead(II) sulfide?

Exam 3: Stoichiometry of Formulas and Equations

In combustion analysis, the carbon and hydrogen contents of a substance are determined from the CO2 and H2O, respectively, which are collected in the absorbers.

The formula CH3O0.5 is an example of an empirical formula.

Balance the following equation for the combustion of benzene: C6H6(l) + O2(g) → H2O(g) + CO2(g)

Constitutional (structural) isomers have the same molecular formula but different structural formulas.

Lead (II) nitrate is a poisonous substance which has been used in the manufacture of special explosives and as a sensitizer in photography. Calculate the mass of lead in 139 g of Pb(NO3) 2.

Methanol (CH4O) is converted to bromomethane (CH3Br) as follows: CH4O + HBr → CH3Br + H2O If 12.23 g of bromomethane are produced when 5.00 g of methanol is reacted with excess HBr, what is the percentage yield?

Phosphorus pentachloride, PCl5, a white solid that has a pungent, unpleasant odor, is used as a catalyst for certain organic reactions. Calculate the number of moles in 38.7 g of PCl5.

Hydroxylamine nitrate contains 29.17 mass % N, 4.20 mass % H, and 66.63 mass % O. Determine its empirical formula.

In a correctly balanced equation, the number of reactant molecules must equal the number of product molecules. A)118.15 g/mol B)99.15 g/mol C)78.07 g/mol D)59.08 g/mol E)50.01 g/mol

Potassium chloride is used as a substitute for sodium chloride for individuals with high blood pressure. Identify the limiting reactant and determine the mass of the excess reactant remaining when 7.00 g of chlorine gas reacts with 5.00 g of potassium to form potassium chloride.

Potassium chlorate (used in fireworks, flares, and safety matches) forms oxygen and potassium chloride when heated. KClO3(s) → KCl(s) + O2(g) [unbalanced] How many grams of oxygen are formed when 26.4 g of potassium chlorate is heated?

Balance the following equation: C8H18O3(l) + O2(g) → H2O(g) + CO2(g)

A compound containing chromium and silicon contains 73.52 mass percent chromium. Determine its empirical formula.

Gadolinium oxide, a colorless powder which absorbs carbon dioxide from the air, contains 86.76 mass % Gd. Determine its empirical formula.

Constitutional (structural) isomers have the same empirical formula but different molecular formulas.

A compound of bromine and fluorine is used to make UF6, which is an important chemical in processing and reprocessing of nuclear fuel. The compound contains 58.37 mass percent bromine. Determine its empirical formula.

One mole of methane (CH4) contains a total of 3 × 1024 atoms.

Household sugar, sucrose, has the molecular formula C12H22O11. What is the percent of carbon in sucrose, by mass?

Lead(II) sulfide was once used in glazing earthenware. It will also react with hydrogen peroxide to form lead(II) sulfate and water. How many grams of hydrogen peroxide are needed to react completely with 265 g of lead(II) sulfide?

In combustion analysis, the carbon and hydrogen contents of a substance are determined from the CO₂ and H₂O, respectively, which are collected in the absorbers.

The formula CH₃O_0.5 is an example of an empirical formula.

Balance the following equation for the combustion of benzene: C₆H₆(l) + O₂(g) → H₂O(g) + CO₂(g)

Lead (II) nitrate is a poisonous substance which has been used in the manufacture of special explosives and as a sensitizer in photography. Calculate the mass of lead in 139 g of Pb(NO₃) ₂.

Methanol (CH₄O) is converted to bromomethane (CH₃Br) as follows: CH₄O + HBr → CH₃Br + H₂O If 12.23 g of bromomethane are produced when 5.00 g of methanol is reacted with excess HBr, what is the percentage yield?

Phosphorus pentachloride, PCl₅, a white solid that has a pungent, unpleasant odor, is used as a catalyst for certain organic reactions. Calculate the number of moles in 38.7 g of PCl₅.

Potassium chlorate (used in fireworks, flares, and safety matches) forms oxygen and potassium chloride when heated. KClO₃(s) → KCl(s) + O₂(g) [unbalanced] How many grams of oxygen are formed when 26.4 g of potassium chlorate is heated?

Balance the following equation: C₈H₁₈O₃(l) + O₂(g) → H₂O(g) + CO₂(g)

A compound of bromine and fluorine is used to make UF₆, which is an important chemical in processing and reprocessing of nuclear fuel. The compound contains 58.37 mass percent bromine. Determine its empirical formula.

One mole of methane (CH₄) contains a total of 3 × 10²⁴ atoms.

Household sugar, sucrose, has the molecular formula C₁₂H₂₂O₁₁. What is the percent of carbon in sucrose, by mass?