Question 1

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

Accepted Answer

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 
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 2

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

Accepted Answer

A) True 
 B)False

Question 3

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

Accepted Answer

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

Question 4

Consider the balanced equation:
Al2S3(s) + 6H2O(l) F1F1F1S1F1F1F10 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.

Accepted Answer

a. Water is the limi

Question 5

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

Accepted Answer

A) True 
 B)False

Question 6

Aluminum will react with bromine to form aluminum bromide (used as an acid catalyst in organic synthesis). Al(s) + Br2(l) F1F1F1S1F1F1F10 Al2Br6(s) [unbalanced]
How many moles of Al are needed to form 2.43 mol of Al2Br6?

Accepted Answer

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

Question 7

Balance the following equation: 
B2O3(s) + HF(l) F1F1F1S1F1F1F10 BF3(g) + H2O(l)

Accepted Answer

A)  B2O3(s) + 6HF(l) F1F1F1S1F1F1F10 2BF3(g) + 3H2O(l) 
B)  B2O3(s) + H6F6(l) F1F1F1S1F1F1F10 B2F6(g) + H6O3(l) 
C)  B2O3(s) + 2HF(l) F1F1F1S1F1F1F10 2BF3(g) + H2O(l) 
D)  B2O3(s) + 3HF(l) F1F1F1S1F1F1F10 2BF3(g) + 3H2O(l) 
E)  B2O3(s) + 6HF(l) F1F1F1S1F1F1F10 2BF3(g) + 6H2O(l) 
A)  B2O3(s) + 6HF(l) F1F1F1S1F1F1F10 2BF3(g) + 3H2O(l) 
B)  B2O3(s) + H6F6(l) F1F1F1S1F1F1F10 B2F6(g) + H6O3(l) 
C)  B2O3(s) + 2HF(l) F1F1F1S1F1F1F10 2BF3(g) + H2O(l) 
D)  B2O3(s) + 3HF(l) F1F1F1S1F1F1F10 2BF3(g) + 3H2O(l) 
E)  B2O3(s) + 6HF(l) F1F1F1S1F1F1F10 2BF3(g) + 6H2O(l)

Question 8

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

Accepted Answer

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 
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 9

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

Accepted Answer

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

Question 10

Determine the percent composition of potassium dichromate, K2Cr2O7.

Accepted Answer

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 
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 11

Aluminum oxide (used as an adsorbent or a catalyst for organic reactions) forms when aluminum reacts with oxygen. 4Al(s) + 3O2(g) F1F1F1S1F1F1F10 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?

Accepted Answer

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

Question 12

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

Question 13

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

Accepted Answer

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 
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

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

Accepted Answer

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

Question 15

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) F1F1F1S1F1F1F10 SF4(g) + S2Cl2(l) + 4NaCl(s)

Accepted Answer

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

Question 16

Alkanes are compounds of carbon and hydrogen with the general formula CnH2n+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?

Accepted Answer

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

Question 17

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

Question 18

Balance the following equation:
 UO2(s) + HF(l) F1F1F1S1F1F1F10 UF4(s) + H2O(l)

Accepted Answer

A)  UO2(s) + 2HF(l) F1F1F1S1F1F1F10 UF4(s) + H2O(l) 
B)  UO2(s) + 4HF(l) F1F1F1S1F1F1F10 UF4(s) + 2H2O(l) 
C)  UO2 (s) + H4F4(l) F1F1F1S1F1F1F10 UF4 (s) + H4O2(l) 
D)  UO2(s) + 4HF(l) F1F1F1S1F1F1F10 UF4(s) + 4H2O(l) 
E)  UO2(s) + 8HF(l) F1F1F1S1F1F1F10 2UF4(s) + 4H2O(l) 
A)  UO2(s) + 2HF(l) F1F1F1S1F1F1F10 UF4(s) + H2O(l) 
B)  UO2(s) + 4HF(l) F1F1F1S1F1F1F10 UF4(s) + 2H2O(l) 
C)  UO2 (s) + H4F4(l) F1F1F1S1F1F1F10 UF4 (s) + H4O2(l) 
D)  UO2(s) + 4HF(l) F1F1F1S1F1F1F10 UF4(s) + 4H2O(l) 
E)  UO2(s) + 8HF(l) F1F1F1S1F1F1F10 2UF4(s) + 4H2O(l)

Question 19

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?

Accepted Answer

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

Question 20

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) F1F1F1S1F1F1F10 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.

Accepted Answer

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. 
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.

Exam 3: Stoichiometry of Formulas and Equations

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

The formula CH3O0.5 is an example of an 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.

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?

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

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

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

Determine the percent composition of potassium dichromate, K2Cr2O7.

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.

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

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

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)

Alkanes are compounds of carbon and hydrogen with the general formula CnH2n+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?

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

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

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?

Keys to the Study of Chemistry

The Components of Matter

The Major Classes of Chemical Reactions

Gases and the Kinetic-Molecular Theory

Thermochemistry: Energy Flow and Chemical Change

Quantum Theory and Atomic Structure

Electron Configuration and Chemical Periodicity

Models of Chemical Bonding

The Shapes of Molecules

Theories of Covalent Bonding

Intermolecular Forces: Liquids, Solids, and Phase Changes

The Properties of Mixtures: Solutions and Colloids

Periodic Patterns in the Main Group Elements: Bonding, Structure, and Reactivity

Organic Compounds and the Atomic Properties of Carbon

Kinetics: Rates and Mechanisms of Chemical Reactions

Equilibrium: the Extent of Chemical Reactions

Acid-Base Equilibria

Ionic Equilibria in Aqueous Systems

Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions

Electrochemistry: Chemical Change and Electrical Work

The Elements in Nature and Industry

The Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

Filters

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

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?

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

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

Determine the percent composition of potassium dichromate, K₂Cr₂O₇.

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.

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

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)

Alkanes are compounds of carbon and hydrogen with the general formula C_nH₂_n₊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?

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

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?