Question 1

Unknown Compound Combustion: A 6.0 g compound produces 8.8 g of CO₂ and 3.6 g of H₂O upon combustion. What is its empirical formula?

• (A) CH
• (B) CH₂O
• (C) C₂H₄O
• (D) CH₄O

Question 2

Ammonia Formation: N₂ + 3H₂ → 2NH₃. Calculate the number of molecules of ammonia formed when 44.8 L of nitrogen reacts with 6.0 g of hydrogen at STP.

• (A) 6.02 × 10²³ molecules
• (B) 1.20 × 10²⁴ molecules
• (C) 3.01 × 10²³ molecules
• (D) 1.80 × 10²⁴ molecules

Question 3

Percent Yield Calculation: In the synthesis of ammonia (NH₃), the theoretical yield is 45 g. If 30 g of ammonia are actually produced, what is the percent yield?

• (A) 66.7%
• (B) 75%
• (C) 88.9%
• (D) 50%

Question 4

Combustion of Hydrocarbon: A 9.0 g hydrocarbon produces 11.0 g of CO₂. What is the mass percent of carbon in the hydrocarbon?

• (A) 27.3%
• (B) 36.4%
• (C) 45.5%
• (D) 72.7%

Question 5

Glass Composition: A glass composition contains 12% Na₂O, 12% CaO, and 76% SiO₂. Arrange them in order of moles from the most to the least.

• (A) SiO₂, CaO, Na₂O
• (B) SiO₂, Na₂O, CaO
• (C) Na₂O, CaO, SiO₂
• (D) Na₂O, SiO₂, CaO

Question 6

Hydrate of Copper Sulfate: A hydrate of CuSO₄ is heated, and its mass decreases from 125 g to 80 g. What is the formula for the hydrate?

• (A) CuSO₄·10H₂O
• (B) CuSO₄·5H₂O
• (C) CuSO₄·2H₂O
• (D) CuSO₄·H₂O

Question 7

Empirical Formula of Sulfur-Oxygen Compound: A sulfur-oxygen compound is 50% oxygen by weight. What is its empirical formula?

• (A) SO
• (B) SO₂
• (C) S₂O₃
• (D) S₂O₅

Question 8

Sodium and Water Reaction: Sodium reacts with water to form 10 L of H₂ at STP. What is the mass of sodium?

• (A) 5 g
• (B) 10 g
• (C) 20 g
• (D) 40 g

Question 9

Atomic Mass of Element X: Four compounds containing element X have masses of 36 g, 54 g, 72 g, and 108 g. What is the possible atomic mass of X?

• (A) 18.0
• (B) 25.0
• (C) 72.0
• (D) 108

Question 10

Equimolar Solution Mixing: If equimolar solutions of NaCl and Pb(NO₃)₂ are mixed, which ion will not be present in significant amounts in the resulting solution after the reaction is completed?

• (A) Na⁺
• (B) Cl⁻
• (C) Pb²⁺
• (D) NO₃⁻

Question 11

Net Ionic Equation: Choose the correct net ionic equation representing the reaction that occurs between a solution of ammonium carbonate and a solution of copper (I) chloride.

• (A) 2Cu⁺(aq) + CO₃²⁻(aq) → Cu₂CO₃(s)
• (B) Cu²⁺(aq) + CO₃²⁻(aq) → CuCO₃(s)
• (C) (NH₄)₂CO₃(aq) + 2CuCl(aq) → 2NH₄Cl(aq) + Cu₂CO₃(s)
• (D) (NH₄)₂CO₃(aq) + 2CuCl(aq) → 2NH₄Cl(s) + Cu₂CO₃(aq)

Question 12

Oxidation State: Which of the following statements about the reaction given below is NOT true?
2Cr³⁺ + 3I₂ + 7H₂O → Cr₂O₇²⁻ + 6I⁻ + 14H⁺

• (A) The oxidation number of chromium changes from +3 to +6.
• (B) The oxidation number of iodine changes from 0 to -1.
• (C) The oxidation number of hydrogen changes from +1 to 0.
• (D) The oxidation number of oxygen remains the same.

Question 13

Precipitate Formation: When aqueous solutions of iron (III) nitrate and sodium carbonate are mixed, what is the formula of the precipitate?

• (A) Fe₃(CO₃)₃
• (B) Fe₂(CO₃)₃
• (C) NaNO₃
• (D) No precipitate would form.

Question 14

Spectator Ions: If solutions containing AgNO₃ and KBr are mixed, what are the spectator ions?

• (A) Ag⁺ and Br⁻
• (B) K⁺ and Ag⁺
• (C) K⁺ and NO₃⁻
• (D) Ag⁺, NO₃⁻, K⁺, and Br⁻

Question 15

Half-Reaction Coefficient: …CN⁻ + …OH⁻ → …CNO⁻ + …H₂O + …e⁻
When the half-reaction above is balanced, what is the coefficient for e⁻ if all the coefficients are reduced to the lowest whole number?

• (A) 1
• (B) 2
• (C) 3
• (D) 4

Question 16

Decomposition of Potassium Chlorate: When heated, potassium chlorate decomposes into potassium chloride and oxygen gas via the following reaction:

2 KClO₃(s) → 2 KCl(s) + 3 O₂(g)

If 12.25 g of potassium chlorate decomposes completely, how many grams of oxygen gas are produced?

• (A) 3.00 g
• (B) 4.80 g
• (C) 6.00 g
• (D) 7.20 g

Question 17

Volume of Oxygen Gas: Approximately how many liters of oxygen gas will be evolved at STP when 12.25 g of potassium chlorate decomposes according to the reaction:

2 KClO₃(s) → 2 KCl(s) + 3 O₂(g)

• (A) 2.24 L
• (B) 3.36 L
• (C) 4.48 L
• (D) 22.4 L

Question 18

Effect of Temperature on Gas Pressure: If the temperature of the gas is doubled while the volume is held constant, what will happen to the pressure exerted by the gas and why?

• (A) It will also double, because the gas molecules will be moving faster.
• (B) It will also double, because the gas molecules are exerting a greater force on each other.
• (C) It will be cut in half, because the molecules will lose more energy when colliding.
• (D) It will increase by a factor of 4, because the kinetic energy will be four times greater.

Question 19

Solution Concentration: How many grams of sodium chloride (NaCl) are needed to prepare 500 mL of a 0.5 M NaCl solution?

• (A) 14.6 g
• (B) 29.2 g
• (C) 58.4 g
• (D) 116.8 g

Question 20

Gas Stoichiometry at Non-STP Conditions: What volume will 2.0 moles of an ideal gas occupy at a pressure of 2.0 atm and a temperature of 273 K?

• (A) 22.4 L
• (B) 11.2 L
• (C) 24.0 L
• (D) 44.8 L

Question 21

Gas Laws Application: A gas occupies 5.0 liters at a pressure of 1.0 atm. What will be its volume if the pressure is increased to 2.5 atm while the temperature remains constant?

• (A) 2.0 L
• (B) 3.0 L
• (C) 5.0 L
• (D) 12.5 L

Question 22

Ideal Gas Law Calculation: How many moles of gas are present in a 10.0 L container at 2.0 atm pressure and 300 K temperature?

• (A) 0.80 mol
• (B) 0.50 mol
• (C) 1.00 mol
• (D) 2.00 mol

Question 23

Precipitate Formation: If solutions of barium nitrate and sodium sulfate are mixed, what will be the formula of the precipitate?

• (A) BaSO₄
• (B) NaNO₃
• (C) Ba(NO₃)₂
• (D) No precipitate will form.

Question 24

Spectator Ions: If solutions containing Na₂SO₄ and CaCl₂ are mixed, which ions are the spectator ions in the resulting solution?

• (A) Na⁺ and Cl⁻
• (B) Ca²⁺ and SO₄²⁻
• (C) Na⁺ and SO₄²⁻
• (D) Ca²⁺ and Cl⁻

Question 25

Equilibrium of Ions: If equimolar solutions of Na₂CO₃ and Mg(NO₃)₂ are mixed, which ion will NOT be present in significant amounts in the resulting solution after equilibrium is established?

• (A) Na⁺
• (B) CO₃²⁻
• (C) NO₃⁻
• (D) Mg²⁺

Question 26

Net Ionic Equation: Choose the correct net ionic equation representing the reaction that occurs when solutions of silver nitrate and sodium carbonate are mixed.

• (A) AgNO₃(aq) + Na₂CO₃(aq) → NaNO₃(aq) + Ag₂CO₃(s)
• (B) 2Ag⁺(aq) + CO₃²⁻(aq) → Ag₂CO₃(s)
• (C) Ag⁺(aq) + CO₃²⁻(aq) → Ag₂CO₃(aq)
• (D) 2Ag⁺(aq) + 2NO₃⁻ → AgNO₃(s)

Question 27

Stoichiometry of Combustion: When 8.0 grams of methane (CH₄) is combusted in excess oxygen, how many grams of carbon dioxide (CO₂) will be produced?

• (A) 22.0 g
• (B) 44.0 g
• (C) 88.0 g
• (D) 16.0 g

Question 28

Stoichiometry of Acid-Base Reaction: How many grams of sodium hydroxide (NaOH) are needed to completely neutralize 50.0 mL of 0.5 M sulfuric acid (H₂SO₄)?

• (A) 2.0 g
• (B) 4.0 g
• (C) 8.0 g
• (D) 1.0 g

Question 29

Limiting Reagent: If 14.0 grams of nitrogen (N₂) react with 6.0 grams of hydrogen (H₂) to form ammonia (NH₃), what is the limiting reagent and how many grams of ammonia will be produced?

• (A) N₂; 17.0 g
• (B) H₂; 34.0 g
• (C) N₂; 34.0 g
• (D) H₂; 17.0 g

Question 30

Gas Stoichiometry: How many liters of hydrogen gas at STP are produced when 10.0 grams of zinc react with excess hydrochloric acid according to the reaction:

Zn + 2HCl → ZnCl₂ + H₂

• (A) 3.42 L
• (B) 4.48 L
• (C) 7.85 L
• (D) 11.2 L

Question 31

Percent Yield Calculation: When 50.0 grams of calcium carbonate (CaCO₃) is decomposed, it produces 20.0 grams of calcium oxide (CaO). If the theoretical yield is 28.0 grams, what is the percent yield of the reaction?

• (A) 50%
• (B) 71.4%
• (C) 75%
• (D) 85.7%

Question 32

Percent Error Calculation: During an experiment, 0.85 moles of hydrogen gas was collected. The theoretical amount was calculated to be 1.00 mole. What is the percent error of the experiment?

• (A) 8.5%
• (B) 10.0%
• (C) 15.0%
• (D) 20.0%

Question 33

Limiting Reagent and Stoichiometry: If 10.0 grams of sulfuric acid (H₂SO₄) reacts with 10.0 grams of sodium hydroxide (NaOH), what mass of sodium sulfate (Na₂SO₄) will be formed?

• (A) 12.5 g
• (B) 14.2 g
• (C) 17.5 g
• (D) 20.0 g

Question 34

Gas Stoichiometry: How many liters of carbon dioxide (CO₂) gas at STP will be produced when 5.0 grams of calcium carbonate (CaCO₃) decomposes?

• (A) 1.12 L
• (B) 2.24 L
• (C) 3.36 L
• (D) 4.48 L

Question 35

Mass-to-Mass Stoichiometry: How many grams of water (H₂O) will be produced when 10.0 grams of hydrogen gas (H₂) reacts completely with oxygen gas (O₂)?

• (A) 90.0 g
• (B) 80.0 g
• (C) 100.0 g
• (D) 180.0 g

Question 36

Excess Reagent Calculation: If 20.0 grams of magnesium reacts with 10.0 grams of hydrochloric acid (HCl), what is the mass of excess magnesium left after the reaction?

• (A) 5.2 g
• (B) 9.8 g
• (C) 10.0 g
• (D) 15.0 g

Question 37

Limiting Reagent and Percent Yield: When 15.0 grams of aluminum reacts with 50.0 grams of iron(III) oxide (Fe₂O₃), how many grams of iron (Fe) will be produced if the reaction has a 75% yield? The balanced equation for the reaction is: 2Al + Fe₂O₃ → Al₂O₃ + 2Fe.

• (A) 20.5 g
• (B) 30.0 g
• (C) 35.5 g
• (D) 40.0 g

Question 38

Combustion Analysis: A 10.0 g sample of a hydrocarbon is completely burned in oxygen, producing 33.0 g of CO₂ and 13.5 g of H₂O. Determine the empirical formula of the hydrocarbon.

• (A) CH
• (B) C₂H₄
• (C) C₃H₆
• (D) C₄H₈

Question 39

Gas Collection Over Water: In an experiment, 2.00 grams of zinc reacts with excess hydrochloric acid to produce hydrogen gas. The gas is collected over water at 25°C, where the vapor pressure of water is 24 mmHg. If the total pressure in the container is 780 mmHg, what is the volume of the dry hydrogen gas collected at STP?

• (A) 0.745 L
• (B) 0.815 L
• (C) 0.930 L
• (D) 1.10 L

Question 40

Back Titration: A sample of impure limestone weighing 2.50 grams is dissolved in 50.0 mL of 1.0 M hydrochloric acid (HCl). The excess acid is then back-titrated with 0.50 M sodium hydroxide (NaOH), requiring 30.0 mL to reach the endpoint. Calculate the percentage purity of the limestone (assumed to be CaCO₃).

• (A) 65.0%
• (B) 70.0%
• (C) 75.0%
• (D) 85.0%

Question 41

Equilibrium Constant: At a certain temperature, the equilibrium constant for the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g) is K_eq = 0.500. If [N₂] = 0.200 M, [H₂] = 0.300 M, and [NH₃] = 0.400 M, is the system at equilibrium?

• (A) Yes
• (B) No, the reaction will shift left.
• (C) No, the reaction will shift right.
• (D) Cannot be determined.

Question 42

Stoichiometry and Mass Conservation: A 10.0 g sample of calcium carbonate (CaCO₃) is heated strongly until it decomposes completely into calcium oxide (CaO) and carbon dioxide (CO₂), according to the reaction:

CaCO₃(s) → CaO(s) + CO₂(g)

Calculate the mass of calcium oxide produced.

• (A) 5.60 g
• (B) 8.40 g
• (C) 10.0 g
• (D) 4.40 g

Question 43

Stoichiometry: In a reaction between 5.00 g of aluminum (Al) and 20.00 g of chlorine gas (Cl₂), what is the limiting reagent? How many grams of aluminum chloride (AlCl₃) are produced?

• (A) Al is the limiting reagent; 13.33 g AlCl₃ produced.
• (B) Cl₂ is the limiting reagent; 26.67 g AlCl₃ produced.
• (C) Al is the limiting reagent; 26.67 g AlCl₃ produced.
• (D) Cl₂ is the limiting reagent; 13.33 g AlCl₃ produced.

Question 44

Stoichiometry in Gas Reactions: When 10.0 grams of propane (C₃H₈) is combusted in excess oxygen, how many liters of carbon dioxide (CO₂) are produced at STP?

The balanced equation for the combustion reaction is:

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

• (A) 22.4 L
• (B) 33.6 L
• (C) 44.8 L
• (D) 11.2 L

Question 45

Limiting Reagent and Excess: 8.00 g of sodium reacts with 10.00 g of chlorine gas to form sodium chloride. Identify the limiting reagent and calculate the mass of excess reagent remaining after the reaction.

• (A) Na is the limiting reagent; 4.45 g Cl₂ remains.
• (B) Cl₂ is the limiting reagent; 3.55 g Na remains.
• (C) Na is the limiting reagent; 3.55 g Cl₂ remains.
• (D) Cl₂ is the limiting reagent; 4.45 g Na remains.

Question 46

Stoichiometry and Percent Yield: If 25.00 g of iron(III) oxide (Fe₂O₃) reacts with excess carbon monoxide (CO) to produce iron (Fe) and carbon dioxide (CO₂), and the reaction yield is 80.0%, how many grams of iron are produced?

• (A) 14.93 g
• (B) 20.90 g
• (C) 29.85 g
• (D) 40.00 g

Question 47

Reaction Stoichiometry: Ammonium nitrate (NH₄NO₃) decomposes to form nitrogen gas (N₂), water (H₂O), and oxygen gas (O₂). If 16.0 g of NH₄NO₃ decomposes, what volume of oxygen gas is produced at STP?

• (A) 5.60 L
• (B) 8.96 L
• (C) 11.20 L
• (D) 22.40 L

Question 48

Stoichiometry in Solution: A solution of 50.0 mL of 0.500 M sulfuric acid (H₂SO₄) is neutralized by a solution of 0.250 M sodium hydroxide (NaOH). Calculate the volume of NaOH required to completely neutralize the acid.

• (A) 50.0 mL
• (B) 100.0 mL
• (C) 200.0 mL
• (D) 25.0 mL

Question 49

Stoichiometry in Solutions: How many grams of NaCl are needed to prepare 250.0 mL of a 0.500 M solution?

• (A) 7.31 g
• (B) 5.85 g
• (C) 11.70 g
• (D) 2.93 g

Question 50

Titration and Stoichiometry: What volume of 0.200 M HCl is required to completely neutralize 25.00 mL of 0.100 M NaOH?

• (A) 10.00 mL
• (B) 12.50 mL
• (C) 25.00 mL
• (D) 50.00 mL