Deck 3: Stoichiometry of Formulas and Equations

Question 1

How many atoms are in a drop of mercury that has a diameter of 1.0 mm? (Volume of a sphere is 4 $\pi$ r³/3; 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 the above

Answer 1

2.1 × 10¹⁹

Question 2

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 2

233.79 g/mol

Question 3

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 3

4.976 × 10²³ O atoms

Question 4

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

Question 5

A single atom of hydrogen has a mass of 1.0 amu, while a mole of hydrogen atoms has a mass of 1.0 g. Select the correct conversion factor between atomic mass units and grams.

A) 1 amu = 1 g exactly
B) 1 amu = 6.0 × 10²³ g
C) 1 g = 6.0 × 10²³ amu
D) 1 g = 1.7 × 10^-24 amu
E) none of the above

Question 6

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 7

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 8

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 9

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 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

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 12

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 13

A normal breath takes in about 1.0 L of air. Assuming that air has an average molar mass of 28.8 g, 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 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

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 16

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 17

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 18

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 19

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 20

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 21

Balance the following equation:
B₂O₃(s) + HF(l) $\to$ BF₃(g) + H₂O(l)

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

Question 22

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

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

Question 23

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 24

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 25

Balance the following equation:
UO₂(s) + HF(l) $\to$ UF₄(s) + H₂O(l)

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

Question 26

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 27

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 28

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 the above.

Question 29

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 30

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 31

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 32

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 33

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 34

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 the above

Question 35

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 36

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 the above

Question 37

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 38

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 39

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 40

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 41

How many grams of oxygen are needed to react completely with 200.0 g of ammonia, NH₃? 4NH₃(g) + 5O₂(g) $\to$ 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 42

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) $\to$ 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 43

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) $\to$ 2CO(g)
Fe₃O₄(s) + 4CO(g) $\to$ 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 44

Potassium chlorate (used in fireworks, flares, and safety matches) forms oxygen and potassium chloride when heated. KClO₃(s) $\to$ 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 45

Aluminum will react with bromine to form aluminum bromide (used as an acid catalyst in organic synthesis). Al(s) + Br₂(l) $\to$ 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 46

Phosphine, an extremely poisonous and highly reactive gas, will react with oxygen to form tetraphosphorus decaoxide and water. PH₃(g) + O₂(g) $\to$ 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 47

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) $\to$ 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 48

Aluminum oxide (used as an adsorbent or a catalyst for organic reactions) forms when aluminum reacts with oxygen. 4Al(s) + 3O₂(g) $\to$ 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. 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 49

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 50

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) $\to$ 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 51

The iodine "clock reaction" involves the following sequence of reactions occurring in a reaction mixture in a single beaker.
1) IO₃^-(aq) + 5I^-(aq) + 6H⁺(aq) $\to$ 3I₂(aq) + 3H₂O(l)
2) I₂(aq) + 2S₂O₃^2-(aq) $\to$ 2I^-(aq) + S₄O₆^2-(aq)
The molecular iodine (I₂) formed in reaction 1 is immediately used up in reaction 2, so that no iodine accumulates. What is the overall reaction occurring in this experiment?

A)IO₃^-(aq) + 3I^-(aq) + 2S₂O₃^2-(aq) + 6H⁺(aq) $\to$ 2I₂(aq) + S₄O₆^2-(aq) + 3H₂O(l)
B)IO₃^-(aq) + 4S₂O₃^2-(aq) + 6H⁺(aq) $\to$ I^-(aq) + 2S₄O₆^2-(aq) + 3H₂O(l)
C)IO₃^-(aq) + 6S₂O₃^2-(aq) + 6H⁺(aq) $\to$ I^-(aq) + 3S₄O₆^2-(aq) + 3H₂O(l)
D)IO₃^-(aq) + I₂(aq) + 8S₂O₃^2-(aq) + 6H⁺(aq) $\to$ 3I^-(aq) + 4S₄O₆^2-(aq) + 3H₂O(l)
E)IO₃^-(aq) + 2I₂(aq) + 6S₂O₃^2-(aq) + 6H⁺(aq) $\to$ 5I^-(aq) + 3S₄O₆^2-(aq) + 3H₂O(l)

Question 52

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

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

Question 53

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) $\to$ SF₄(g) + S₂Cl₂(l) + 4NaCl(s)

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

Question 54

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

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

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

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) $\to$ 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 57

Balance the following equation:
C₈H₁₈O₃(l) + O₂(g) $\to$ H₂O(g) + CO₂(g)

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

Question 58

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 59

The iodine "clock reaction" involves the following sequence of reactions occurring in a reaction mixture in a single beaker.
1) IO₃^-(aq) + 5I^-(aq) + 6H⁺(aq) $\to$ 3I₂(aq) + 3H₂O(l)
2) I₂(aq) + 2S₂O₃^2-(aq) $\to$ 2I^-(aq) + S₄O₆^2-(aq)
The molecular iodine (I₂) formed in reaction 1 is immediately used up in reaction 2, so that no iodine accumulates. In one experiment, a student made up a reaction mixture which initially contained 0.0020 mol of iodate ions (IO₃^-). If the iodate ions reacted completely, how many moles of thiosulfate ions (S₂O₃^2-) were needed in reaction 2, in order to react completely with the iodine (I₂) produced in reaction 1?

A)0)0020 mol
B)0)0030 mol
C)0)0040 mol
D)0)0050 mol
E)0)0060 mol

Question 60

An important reaction sequence in the industrial production of nitric acid is the following: N₂(g) + 3H₂(g) $\to$ 2NH₃(g)
4NH₃(g) + 5O₂(g) $\to$ 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 61

Analysis of a white solid produced in a reaction between chlorine and phosphorus showed that it contained 77.44% chlorine and 22.56% phosphorus. What is its empirical formula?

Question 62

One mole of O₂ has a mass of 16.0 g.

Question 63

What is the percent yield for the reaction PCl₃(g) + Cl₂(g) $\to$ 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 64

For a sample consisting of 2.50 g of methane, CH₄, calculate
a. the number of moles of methane present.
b. the total number of atoms present.

Question 65

Magnesium (used in the manufacture of light alloys) reacts with iron(III) chloride to form magnesium chloride and iron. 3Mg(s) + 2FeCl₃(s) $\to$ 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 66

Ammonia, NH₃, is produced industrially from nitrogen and hydrogen as follows:
N₂(g) + 3H₂(g) $\to$ 2NH₃(g)
What mass, of which starting material, will remain when 30.0 g of N₂ and 10.0 g of H₂ react until the limiting reagent is completely consumed?

Question 67

Gaseous methanol (CH₄O) reacts with oxygen gas to produce carbon dioxide gas and liquid water. Write a balanced equation for this process.

Question 68

Balance the equation
B₂O₃(s) + NaOH(aq) $\to$ Na₃BO₃(aq) + H₂O(l)

Question 69

In 0.20 mole of phosphoric acid, H₃PO₄
a. how many H atoms are there?
b. what is the total number of atoms?
c. how many moles of O atoms are there?

Question 70

Methanol (CH₄O) is converted to bromomethane (CH₃Br) as follows:
CH₄O + HBr $\to$ 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 71

Tetraphosphorus hexaoxide ( = 219.9 g/mol) is formed by the reaction of phosphorus with oxygen gas. P₄(s) + 3O₂(g) $\to$ 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 72

Consider the balanced equation for the combustion of propane, C₃H₈
C₃H₈(g) + 5O₂(g) $\to$ 3CO₂(g) + 4H₂O(l)
If propane reacts with oxygen as above
a. what is the limiting reagent in a mixture containing 5.00 g of C₃H₈ and 10.0 g of O₂?
b. what mass of CO₂ is formed when 1.00 g of C₃H₈ reacts completely?

Question 73

The insecticide DDT was formerly in widespread use, but now it is severely restricted owing to its adverse environmental effects. It is prepared as follows:
C₂HCl₃O + 2C₆H₅Cl $\to$ C₁₄H₉Cl₅ + H₂O
chloral chlorobenzene DDT
If 10.00 g of chloral were reacted with 10.00 g of chlorobenzene
a. what is the maximum amount (mol) of DDT which could be formed?
b. what is the limiting reagent?
c. what is the % yield, if 12.15 g of DDT is produced?

Question 74

A compound consisting of C, H, and O only, has a molar mass of 331.5 g/mol. Combustion of 0.1000 g of this compound caused a 0.2921 g increase in the mass of the CO₂ absorber and a 0.0951 g increase in the mass of the H₂O absorber. What is the empirical formula of the compound?

Question 75

Balance the following equation for the combustion of butane, a hydrocarbon used in gas lighters:
C₄H₁₀(g) + O₂(g) $\to$ CO₂(g) + H₂O(l)

Question 76

Balance the following equation for partial oxidation of ammonia, an important reaction in the production of nitric acid:
NH₃(g) + O₂(g) $\to$ NO(g) + H₂O(l)

Question 77

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 78

Propane, C₃H₈, is commonly provided as a bottled gas for use as a fuel. In 0.200 mol of propane
a. what is the mass of propane?
b. what mass of carbon is present?
c. how many molecules of C₃H₈ are present?
d. how many hydrogen atoms are present?

Question 79

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) $\to$ 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 80

Consider the balanced equation:
Al₂S₃(s) + 6H₂O(l) $\to$ 2Al(OH)₃(s) + 3H₂S(g)
If 15.0g of aluminum sulfide and 10.0g of water are allowed to react as above, and assuming a complete reaction
a. by calculation, find out which is the limiting reagent.
b. calculate the maximum mass of H₂S which can be formed from these reagents.
c. calculate the mass of excess reagent remaining after the reaction is complete.