Deck 3: Stoichiometry of Formulas and Equations

Question 1

Calculate the molar mass of Ca(BO₂)₂·6H₂O.

A) 273.87 g/mol
B) 233.79 g/mol
C) 183.79 g/mol
D) 174.89 g/mol
E) 143.71 g/mol

Answer 1

233.79 g/mol

Question 2

Calculate the number of oxygen atoms in 29.34 g of sodium sulfate, Na₂SO₄.

A) 1.244 × 10²³ O atoms
B) 4.976 × 10²³ O atoms
C) 2.409 × 10²⁴ O atoms
D) 2.915 × 10²⁴ O atoms
E) 1.166 × 10²⁵ O atoms

Answer 2

4.976 × 10²³ O atoms

Question 3

Sulfur trioxide can react with atmospheric water vapor to form sulfuric acid that falls as acid rain. Calculate the mass in grams of 3.65 × 10²⁰ molecules of SO₃.

A) 6.06 × 10^-4 g
B) 2.91 × 10^-2 g
C) 4.85 × 10^-2 g
D) 20.6 g
E) 1650 g

Answer 3

4.85 × 10^-2 g

Question 4

Calculate the molar mass of (NH₄)₃AsO₄.

A) 417.80 g/mol
B) 193.03 g/mol
C) 165.02 g/mol
D) 156.96 g/mol
E) 108.96 g/mol

Question 5

Aluminum sulfate, Al₂(SO₄)₃, is used in tanning leather, purifying water, and manufacture of antiperspirants. Calculate its molar mass.

A) 450.06 g/mol
B) 342.15 g/mol
C) 315.15 g/mol
D) 278.02 g/mol
E) 74.98 g/mol

Question 6

Which of the following samples has the most moles of the compound?

A) 50.0 g of Li₂O
B) 75.0 g of CaO
C) 200.0 g of Fe₂O₃
D) 50.0 g of CO₂
E) 100.0 g of SO₃

Question 7

Aluminum oxide, Al₂O₃, is used as a filler for paints and varnishes as well as in the manufacture of electrical insulators. Calculate the number of moles in 47.51 g of Al₂O₃.

A) 2.377 mol
B) 2.146 mol
C) 1.105 mol
D) 0.4660 mol
E) 0.4207 mol

Question 8

Sodium bromate is used in a mixture which dissolves gold from its ores. Calculate the mass in grams of 4.68 mol of sodium bromate.

A) 706 g
B) 482 g
C) 383 g
D) 32.2 g
E) 0.0310 g

Question 9

Magnesium fluoride is used in the ceramics and glass industry. What is the mass of 1.72 mol of magnesium fluoride?

A) 43.3 g
B) 62.3 g
C) 74.5 g
D) 92.9 g
E) 107 g

Question 10

Which of the following samples contains the greatest total number atoms?

A) 50.0 g of Li₂O
B) 75.0 g of CaO
C) 200.0 g of Fe₂O₃
D) 50.0 g of CO₂
E) 100.0 g of SO₃

Question 11

Calculate the molar mass of rubidium carbonate, Rb₂CO₃.

A) 340.43 g/mol
B) 255.00 g/mol
C) 230.94 g/mol
D) 145.47 g/mol
E) 113.48 g/mol

Question 12

Calculate the mass in grams of 8.35 × 10²² molecules of CBr₄.

A) 0.0217 g
B) 0.139 g
C) 7.21 g
D) 12.7 g
E) 46.0 g

Question 13

Calculate the molar mass of tetraphosphorus decaoxide, P₄O₁₀, a corrosive substance which can be used as a drying agent.

A) 469.73 g/mol
B) 283.89 g/mol
C) 190.97 g/mol
D) 139.88 g/mol
E) 94.97 g/mol

Question 14

Potassium dichromate, K₂Cr₂O₇, is used in tanning leather, decorating porcelain, and water proofing fabrics. Calculate the number of chromium atoms in 78.82 g of K₂Cr₂O₇.

A) 9.490 × 10²⁵ Cr atoms
B) 2.248 × 10²⁴ Cr atoms
C) 1.124 × 10²⁴ Cr atoms
D) 3.227 × 10²³ Cr atoms
E) 1.613 × 10²³ Cr atoms

Question 15

What is the mass in grams of 0.250 mol of the common antacid calcium carbonate?

A) 4.00 × 10² g
B) 25.0 g
C) 17.0 g
D) 4.00 × 10^-2 g
E) 2.50 × 10^-3 g

Question 16

How many atoms are in a drop of mercury that has a diameter of 1.0 mm? (Volume of a sphere is 4πr³/3; density of mercury = 13.6 g/cm³)

A) 2.1 × 10¹⁹
B) 1.7 × 10²⁰
C) 2.1 × 10²²
D) 1.7 × 10²³
E) None of these choices are correct.

Question 17

Calcium fluoride, CaF₂, is a source of fluorine and is used to fluoridate drinking water. Calculate its molar mass.

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

Question 18

Calculate the number of moles in 17.8 g of the antacid magnesium hydroxide, Mg(OH)₂.

A) 3.28 mol
B) 2.32 mol
C) 0.431 mol
D) 0.305 mol
E) 0.200 mol

Question 19

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.

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

Question 20

A normal breath takes in about 1.0 L of air. Assuming that air has an average molar mass of 28.8g, and that its density is 0.97 g/L, how many molecules of air do you take in with each breath?

A) 2.0 × 10²²
B) 2.2 × 10²²
C) 5.8 × 10²³
D) 1.7 × 10²⁵
E) 1.8 × 10²⁵

Question 21

Terephthalic acid, used in the production of polyester fibers and films, is composed of carbon, hydrogen, and oxygen. When 0.6943 g of terephthalic acid was subjected to combustion analysis it produced 1.471 g CO₂ and 0.226 g H₂O. What is its empirical formula?

A) C₂H₃O₄
B) C₃H₄O₂
C) C₄H₃O₂
D) C₅H₁₂O₄
E) C₂H₂O

Question 22

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.

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

Question 23

Analysis of a carbohydrate showed that it consisted of 40.0 % C, 6.71 % H, and 53.3 % O by mass. Its molecular mass was found to be between 140 and 160 amu. What is the molecular formula of this compound?

A) C₄H₈O₆
B) C₅H₁₀O₅
C) C₅H₁₂O₅
D) C₆H₁₂O₄
E) None of these choices are correct.

Question 24

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

A) C₆H₆(l) + 9O₂(g) → 3H₂O(g) + 6CO₂(g)
B) C₆H₆(l) + 9O₂(g) → 6H₂O(g) + 6CO₂(g)
C) 2C₆H₆(l) + 15O₂(g) → 6H₂O(g) + 12CO₂(g)
D) C₆H₆(l) + 15O₂(g) → 3H₂O(g) + 6CO₂(g)
E) 2C₆H₆(l) + 9O₂(g) → 6H₂O(g) + 12CO₂(g)

Question 25

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

A) Gd₂O₃
B) Gd₃O₂
C) Gd₃O₄
D) Gd₄O₃
E) GdO

Question 26

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

A) CrSi₃
B) Cr₂Si₃
C) Cr₃Si
D) Cr₃Si₂
E) Cr₂S

Question 27

Copper(II) sulfate pentahydrate, CuSO₄·5H₂O, is used as a fungicide and algicide. Calculate the mass of oxygen in 1.000 mol of CuSO₄·5H₂O.

A) 249.7 g
B) 144.0 g
C) 96.00 g
D) 80.00 g
E) 64.00 g

Question 28

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.

A) BrF
B) BrF₂
C) Br₂F₃
D) Br₃F
E) BrF₃

Question 29

Terephthalic acid, used in the production of polyester fibers and films, is composed of carbon, hydrogen, and oxygen. When 0.6943 g of terephthalic acid was subjected to combustion analysis it produced 1.471 g CO₂ and 0.226 g H₂O. If its molar mass is between 158 and 167 g/mol, what is its molecular formula?

A) C₄H₆O₇
B) C₆H₈O₅
C) C₇H₁₂O₄
D) C₄H₃O₂
E) C₈H₆O₄

Question 30

Balance the following equation: UO₂(s) + HF(l) → UF₄(s) + H₂O(l)

A) UO₂(s) + 2HF(l) → UF₄(s) + H₂O(l)
B) UO₂(s) + 4HF(l) → UF₄(s) + 2H₂O(l)
C) UO₂(s) + H₄F₄(l) → UF₄ (s) + H₄O₂(l)
D) UO₂(s) + 4HF(l) → UF₄(s) + 4H₂O(l)
E) UO₂(s) + 8HF(l) → 2UF₄(s) + 4H₂O(l)

Question 31

How many protons are there in a molecule of adrenaline (C₉H₁₃NO₃), a neurotransmitter and hormone?

A) 22
B) 26
C) 43
D) 98
E) 183

Question 32

In the combustion analysis of 0.1127 g of glucose (C₆H₁₂O₆), what mass, in grams, of CO₂ would be produced?

A) 0.0451 g
B) 0.0825 g
C) 0.1652 g
D) 0.4132 g
E) 1.466 g

Question 33

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

A) HNO
B) H₂NO₂
C) HN₆O₁₆
D) HN₁₆O₇
E) H₂NO₃

Question 34

Hydroxylamine hydrochloride is a powerful reducing agent which is used as a polymerization catalyst. It contains 5.80 mass % H, 20.16 mass % N, 23.02 mass % O, and 51.02 mass % Cl. What is its empirical formula?

A) H₂N₇O₈Cl₁₈
B) H₂N₂O₂Cl
C) HN₃O₄Cl₉
D) H₄NOCl
E) H₄NOCl₂

Question 35

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

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

Question 36

Hydroxylamine nitrate contains 29.17 mass % N, 4.20 mass % H, and 66.63 mass O. If its molar mass is between 94 and 98 g/mol, what is its molecular formula?

A) NH₂O₅
B) N₂H₄O₄
C) N₃H₃O₃
D) N₄H₈O₂
E) N₂H₂O₄

Question 37

The number of hydrogen atoms in 0.050 mol of C₃H₈O₃ is

A) 3.0 × 10²² H atoms.
B) 1.2 × 10²³ H atoms.
C) 2.4 × 10²³ H atoms.
D) 4.8 × 10²³ H atoms.
E) None of these choices are correct.

Question 38

Balance the following equation: B₂O₃(s) + HF(l) → BF₃(g) + H₂O(l)

A) B₂O₃(s) + 6HF(l) → 2BF₃(g) + 3H₂O(l)
B) B₂O₃ (s) + H₆F₆(l) → B₂F₆(g) + H₆O₃(l)
C) B₂O₃ (s) + 2HF(l) → 2BF₃(g) + H₂O(l)
D) B₂O₃ (s) + 3HF(l) → 2BF₃(g) + 3H₂O(l)
E) B₂O₃ (s) + 6HF(l) → 2BF₃(g) + 6H₂O(l)

Question 39

Alkanes are compounds of carbon and hydrogen with the general formula C_nH_2n+2. An alkane component of gasoline has a molar mass of between 125 and 130 g/mol. What is the value of n for this alkane?

A) 4
B) 9
C) 10
D) 13
E) 14

Question 40

Determine the percent composition of potassium dichromate, K₂Cr₂O₇.

A) 17.5% K, 46.6% Cr, 35.9% O
B) 29.8% K, 39.7% Cr, 30.5% O
C) 36.5% K, 48.6% Cr, 14.9% O
D) 37.2% K, 24.7% Cr, 38.1% O
E) None of these choices are correct.

Question 41

Aluminum oxide (used as an adsorbent or a catalyst for organic reactions) forms when aluminum reacts with oxygen. 4Al(s) + 3O₂(g) → 2Al₂O₃(s)
A mixture of 82.49 g of aluminum ( = 26.98 g/mol) and 117.65 g of oxygen ( = 32.00g/mol) is allowed to react. What mass of aluminum oxide ( = 101.96 g/mol) can be formed?

A) 155.8 g
B) 200.2 g
C) 249.9 g
D) 311.7 g
E) 374.9 g

Question 42

Magnesium reacts with iron(III) chloride to form magnesium chloride (which can be used in fireproofing wood and in disinfectants) and iron. 3Mg(s) + 2FeCl₃(s) → 3MgCl₂(s) + 2Fe(s)
A mixture of 41.0 g of magnesium ( = 24.31 g/mol) and 175 g of iron(III) chloride ( = 162.2 g/mol) is allowed to react. What mass of magnesium chloride = 95.21 g/mol) is formed?

A) 68.5 g MgCl₂
B) 77.0 g MgCl₂
C) 71.4 g MgCl₂
D) 107 g MgCl₂
E) 154 g MgCl₂

Question 43

Magnesium (used in the manufacture of light alloys) reacts with iron(III) chloride to form magnesium chloride and iron. 3Mg(s) + 2FeCl₃(s) → 3MgCl₂(s) + 2Fe(s) A mixture of 41.0 g of magnesium ( = 24.31 g/mol) and 175 g of iron(III) chloride ( = 162.2 g/mol) is allowed to react. Identify the limiting reactant and determine the mass of the excess reactant present in the vessel when the reaction is complete.

A) Limiting reactant is Mg; 67 g of FeCl₃ remain.
B) Limiting reactant is Mg; 134 g of FeCl₃ remain.
C) Limiting reactant is Mg; 104 g of FeCl₃ remain.
D) Limiting reactant is FeCl₃; 2 g of Mg remain.
E) Limiting reactant is FeCl₃; 87 g of Mg remain.

Question 44

Balance the following equation: Ca₃(PO₄)₂(s) + SiO₂(s) + C(s) → CaSiO₃(s) + CO(g) + P₄(s)

A) Ca₃(PO₄)₂(s) + 3SiO₂(s) + 8C(s) → 3CaSiO₃(s) + 8CO(g) + P₄(s)
B) Ca₃(PO₄)₂(s) + 3SiO₂(s) + 14C(s) → 3CaSiO₃(s) + 14CO(g) + P₄(s)
C) Ca₃(PO₄)₂(s) + 3SiO₂(s) + 8C(s) → 3CaSiO₃(s) + 8CO(g) + 2P₄(s)
D) 2Ca₃(PO₄)₂(s) + 6SiO₂(s) + 10C(s) → 6CaSiO₃(s) + 10CO(g) + P₄(s)
E) 2Ca₃(PO₄)₂(s) + 6SiO₂(s) + 10C(s) → 6CaSiO₃(s) + 10CO(g) + 4P₄(s)

Question 45

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?

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

Question 46

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.

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 47

Aluminum will react with bromine to form aluminum bromide (used as an acid catalyst in organic synthesis). Al(s) + Br₂(l) → Al₂Br₆(s) [unbalanced]
How many moles of Al are needed to form 2.43 mol of Al₂Br₆?

A) 7.29 mol
B) 4.86 mol
C) 2.43 mol
D) 1.62 mol
E) 1.22 mol

Question 48

How many molecules of molecular oxygen react with four molecules of NH₃ to form four molecules of nitrogen monoxide and six molecules of water?

A) 2
B) 10
C) 3
D) 4
E) 5

Question 49

How many grams of sodium fluoride (used in water fluoridation and manufacture of insecticides) are needed to form 485 g of sulfur tetrafluoride? 3SCl₂(l) + 4NaF(s) → SF₄(g) + S₂Cl₂(l) + 4NaCl(s)

A) 1940 g
B) 1510 g
C) 754 g
D) 205 g
E) 51.3 g

Question 50

An important reaction sequence in the industrial production of nitric acid is the following: N₂(g) + 3H₂(g) → 2NH₃(g)
4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(l)
Starting from 20.0 mol of nitrogen gas in the first reaction, how many moles of oxygen gas are required in the second one?

A) 12.5 mol O₂
B) 20.0 mol O₂
C) 25.0 mol O₂
D) 50.0 mol O₂
E) 100. mol O₂

Question 51

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

A) C₈H₁₈O₃(l) + 8O₂(g) → 9H₂O(g) + 8CO₂(g)
B) C₈H₁₈O₃(l) + 11O₂(g) → 9H₂O(g) + 8CO₂(g)
C) 2C₈H₁₈O₃(l) + 22O₂(g) → 9H₂O(g) + 16CO₂(g)
D) C₈H₁₈O₃(l) + 13O₂(g) → 18H₂O(g) + 8CO₂(g)
E) 2C₈H₁₈O₃(l) + 17O₂(g) → 18H₂O(g) + 16CO₂(g)

Question 52

Sulfur dioxide reacts with chlorine to produce thionyl chloride (used as a drying agent for inorganic halides) and dichlorine oxide (used as a bleach for wood, pulp, and textiles). SO₂(g) + 2Cl₂(g) → SOCl₂(g) + Cl₂O(g)
If 0.400 mol of Cl₂ reacts with excess SO₂, how many moles of Cl₂O are formed?

A) 0.800 mol
B) 0.400 mol
C) 0.200 mol
D) 0.100 mol
E) 0.0500 mol

Question 53

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?

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 54

How many grams of oxygen are needed to react completely with 200.0 g of ammonia, NH₃? 4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(g)

A) 469.7 g
B) 300.6 g
C) 250.0 g
D) 3.406 g
E) 2.180 g

Question 55

Aluminum metal reacts with chlorine gas to form solid aluminum trichloride, AlCl₃. What mass of chlorine gas is needed to react completely with 163 g of aluminum?

A) 214 g
B) 245 g
C) 321 g
D) 489 g
E) 643 g

Question 56

Phosphine, an extremely poisonous and highly reactive gas, will react with oxygen to form tetraphosphorus decaoxide and water. PH₃(g) + O₂(g) → P₄O₁₀(s) + H₂O(g) [unbalanced]
Calculate the mass of P₄O₁₀(s) formed when 225 g of PH₃ reacts with excess oxygen.

A) 1880 g
B) 940. g
C) 900. g
D) 470 g
E) 56.3 g

Question 57

Ammonia, an important source of fixed nitrogen that can be metabolized by plants, is produced using the Haber process in which nitrogen and hydrogen combine. N₂(g) + 3H₂(g) → 2NH₃(g)
How many grams of nitrogen are needed to produce 325 grams of ammonia?

A) 1070 g
B) 535 g
C) 267 g
D) 178 g
E) 108 g

Question 58

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?

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

Question 59

Ammonia will react with fluorine to produce dinitrogen tetrafluoride and hydrogen fluoride (used in production of aluminum, in uranium processing, and in frosting of light bulbs). 2NH₃(g) + 5F₂(g) → N₂F₄(g) + 6HF(g)
How many moles of NH₃ are needed to react completely with 13.6 mol of F₂?

A) 34.0 mol
B) 27.2 mol
C) 6.80 mol
D) 5.44 mol
E) 2.27 mol

Question 60

Aluminum reacts with oxygen to produce aluminum oxide which can be used as an adsorbent, desiccant, or catalyst for organic reactions. 4Al(s) + 3O₂(g) → 2Al₂O₃(s)
A mixture of 82.49 g of aluminum ( = 26.98 g/mol) and 117.65 g of oxygen ( = 32.00 g/mol) is allowed to react. Identify the limiting reactant and determine the mass of the excess reactant present in the vessel when the reaction is complete.

A) Oxygen is the limiting reactant; 19.81 g of aluminum remain.
B) Oxygen is the limiting reactant; 35.16 g of aluminum remain.
C) Aluminum is the limiting reactant; 16.70 g of oxygen remain.
D) Aluminum is the limiting reactant; 35.16 g of oxygen remain.
E) Aluminum is the limiting reactant; 44.24 g of oxygen remain.

Question 61

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?

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

Question 62

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

Question 63

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

Question 64

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

Question 65

What is the percent yield for the reaction PCl₃(g) + Cl₂(g) → PCl₅(g)
If 119.3 g of PCl₅ (M = 208.2 g/mol) are formed when 61.3 g of Cl₂ ( = 70.91 g/mol) react with excess PCl3?

A) 195%
B) 85.0%
C) 66.3%
D) 51.4%
E) 43.7%

Question 66

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.

Question 67

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

Question 68

In a correctly balanced equation, the number of reactant molecules must equal the number of product molecules.

Question 69

Tetraphosphorus hexaoxide ( = 219.9 g/mol) is formed by the reaction of phosphorus with oxygen gas. P₄(s) + 3O₂(g) → P₄O₆(s)
If a mixture of 75.3 g of phosphorus and 38.7 g of oxygen produce 43.3 g of P₄O₆, what is the percent yield for the reaction?

A) 57.5%
B) 48.8%
C) 38.0%
D) 32.4%
E) 16.3%

Question 70

In combustion analysis, the oxygen content of a substance is equal to the total oxygen in the CO₂ and H₂O collected in the absorbers.