Stoichiometry Quiz. Stoichiometry is a fundamental concept in chemistry that deals with the quantitative relationships between reactants and products in chemical reactions. Understanding stoichiometry allows students to calculate the amounts of substances involved, predict yields, and solve exam problems accurately. This quiz is designed to test your knowledge of mole calculations, molar ratios, limiting reactants, and reaction yields.
Stoichiometry Quiz: Master Mole Calculations
1. How many moles are in 18 g of water (H₂O)? (H = 1, O = 16)
A. 0.5 mol
B. 1 mol
C. 2 mol
D. 3 mol
2. In the reaction 2H₂ + O₂ → 2H₂O, how many moles of H₂O are produced from 3 moles of H₂?
A. 1 mol
B. 2 mol
C. 3 mol
D. 4 mol
3. What is the molar mass of CO₂? (C = 12, O = 16)
A. 28 g/mol
B. 32 g/mol
C. 44 g/mol
D. 48 g/mol
4. How many molecules are in 2 moles of O₂?
A. 6.02 × 10²³
B. 1.20 × 10²⁴
C. 2 × 10²³
D. 3.01 × 10²³
5. In the reaction N₂ + 3H₂ → 2NH₃, how many moles of H₂ are needed to react with 5 moles of N₂?
A. 5 moles
B. 10 moles
C. 15 moles
D. 20 moles
Stoichiometry Quiz
6. How many grams of NaCl are in 0.5 mol? (Na = 23, Cl = 35.5)
A. 29.25 g
B. 35.5 g
C. 58.5 g
D. 116 g
7. If 10 g of H₂ reacts with excess O₂, how many grams of H₂O are formed? (H = 1, O = 16)
A. 90 g
B. 80 g
C. 100 g
D. 110 g
8. Which of the following represents the correct mole ratio in the reaction 2K + Cl₂ → 2KCl?
A. 1:1:1
B. 2:1:2
C. 2:2:1
D. 1:2:2
9. How many moles of electrons are transferred in the reaction Cu²⁺ + 2e⁻ → Cu?
A. 0.5 mol
B. 1 mol
C. 2 mol
D. 4 mol
10. In the reaction 4Fe + 3O₂ → 2Fe₂O₃, what is the mass of O₂ needed to react with 56 g of Fe? (Fe = 56, O = 16)
A. 24 g
B. 48 g
C. 32 g
D. 64 g
Stoichiometry Quiz
11. How many liters of H₂ gas at STP are produced from 2 moles of H₂?
A. 22.4 L
B. 44.8 L
C. 11.2 L
D. 33.6 L
12. Which of the following is a limiting reactant in the reaction 2Al + 3Cl₂ → 2AlCl₃ if 4 moles Al react with 4 moles Cl₂?
A. Al
B. Cl₂
C. AlCl₃
D. None
13. How many grams of CO₂ are produced from 12 g of C in C + O₂ → CO₂? (C = 12, O = 16)
A. 12 g
B. 16 g
C. 28 g
D. 44 g
14. In the reaction 2Na + 2H₂O → 2NaOH + H₂, how many moles of H₂ are produced from 4 moles of Na?
A. 1 mol
B. 2 mol
C. 3 mol
D. 4 mol
15. Which of the following correctly represents the mole ratio in 2H₂ + O₂ → 2H₂O?
A. 1:1:1
B. 2:1:2
C. 2:2:1
D. 1:2:2
Stoichiometry Quiz
16. If 5 moles of Al react with excess O₂ in 4Al + 3O₂ → 2Al₂O₃, how many moles of Al₂O₃ are produced?
A. 2.5 mol
B. 3 mol
C. 5 mol
D. 7.5 mol
17. How many molecules are in 0.25 mol of H₂O?
A. 1.505 × 10²³
B. 2.405 × 10²³
C. 6.02 × 10²³
D. 0.25 × 10²³
18. Which statement about stoichiometry is correct?
A. It only applies to solid reactions
B. It is used to calculate quantitative relationships in chemical reactions
C. It ignores the mole concept
D. It deals only with energy changes
19. What mass of NaOH is needed to prepare 0.5 dm³ of 1 M solution? (Na = 23, O = 16, H = 1)
A. 20 g
B. 25 g
C. 30 g
D. 40 g
20. In the reaction CaCO₃ → CaO + CO₂, how many moles of CO₂ are produced from 100 g of CaCO₃? (Ca = 40, C = 12, O = 16)
A. 0.5 mol
B. 0.8 mol
C. 1 mol
D. 1.2 mol
Stoichiometry Quiz
21. How many liters of CO₂ at STP are produced from 1 mol of C in C + O₂ → CO₂?
A. 11.2 L
B. 22.4 L
C. 33.6 L
D. 44.8 L
22. In the reaction 2KClO₃ → 2KCl + 3O₂, how many moles of O₂ are produced from 2 moles of KClO₃?
A. 2 mol
B. 3 mol
C. 1.5 mol
D. 4 mol
23. Which of the following is true about the mole concept?
A. 1 mole = 6.02 × 10²³ particles
B. 1 mole = 1 g of substance
C. 1 mole = 12 g of carbon always
D. 1 mole = volume only
24. In the reaction 2Mg + O₂ → 2MgO, how many grams of O₂ are needed to react with 24 g of Mg? (Mg = 24, O = 16)
A. 16 g
B. 24 g
C. 32 g
D. 48 g
25. If 3 moles of H₂ react with 1.5 moles of O₂ in 2H₂ + O₂ → 2H₂O, what is the limiting reactant?
A. H₂
B. O₂
C. H₂O
D. None
Stoichiometry Quiz Answers and Explanations:
1. Answer: B
Explanation: Moles = mass ÷ molar mass → 18 ÷ 18 = 1 mol.
2. Answer: C
Explanation: Mole ratio H₂:H₂O is 2:2 → 3 moles H₂ produces 3 moles H₂O.
3. Answer: C
Explanation: Molar mass = 12 + (16×2) = 44 g/mol.
4. Answer: B
Explanation: 2 moles × 6.02 × 10²³ molecules/mol = 1.204 × 10²⁴ molecules.
5. Answer: C
Explanation: Mole ratio N₂:H₂ = 1:3 → 5×3 = 15 moles H₂.
6. Answer: A
Explanation: M = 0.5 × (23+35.5) = 29.25 g.
7. Answer: A
Explanation: Reaction: 2H₂ + O₂ → 2H₂O. 10 g H₂ = 5 mol H₂ → 5 mol H₂O × 18 g/mol = 90 g? Wait, recalc: 10 g H₂ → 10/2=5 mol? H₂ molar mass=2 g/mol. 10 ÷2 =5 mol H₂. H₂:H₂O=2:2 → 5 mol H₂ → 5 mol H₂O × 18 g/mol=90 g. So correct: 90 g.
8. Answer: B
Explanation: Mole ratio K:Cl₂:KCl = 2:1:2.
9. Answer: C
Explanation: 1 mol Cu²⁺ gains 2 mol e⁻ → for 1 mol reaction, 2 mol electrons transferred.
10. Answer: B
Explanation: 4Fe + 3O₂ → 2Fe₂O₃. 56 g Fe = 1 mol → need 3/4 mol O₂ → 0.75 ×32=24 g? Check: 4 mol Fe:3 mol O₂ → 56 g Fe=1 mol → 1×3/4=0.75 mol O₂ ×32=24 g. Correct: 24 g.
11. Answer: B
Explanation: 1 mol gas = 22.4 L → 2 moles = 44.8 L.
12. Answer: B
Explanation: Al:Cl₂=2:3 → 4 moles Al react with 6 moles Cl₂, only 4 moles Cl₂ available → Cl₂ is limiting reactant.
13. Answer: D
Explanation: 12 g C → 1 mol → 1 mol CO₂ = 12+32=44 g.
14. Answer: B
Explanation: 2Na → 1 H₂ → 4Na → 2 mol H₂.
15. Answer: B
Explanation: Mole ratio H₂:O₂:H₂O=2:1:2.
16. Answer: A
Explanation: 4Al →2 Al₂O₃ → 5 Al → 5×2/4=2.5 mol Al₂O₃.
17. Answer: A
Explanation: 0.25×6.02×10²³=1.505×10²³ molecules.
18. Answer: B
Explanation: Stoichiometry calculates quantitative relationships in reactions.
19. Answer: A
Explanation: 1 M solution = 1 mol/dm³ → 0.5 mol → 0.5×40=20 g.
20. Answer: C
Explanation: CaCO₃=100 g/mol → 100 g=1 mol? Wait, CaCO₃=40+12+48=100 g/mol → 100 g=1 mol → CO₂=12+32=44 g → 1 mol CO₂=44 g. So correct: 1 mol? But answers: 0.8 mol? 100 g/100 g/mol=1 mol → CO₂=1 mol. Correct: C? We can fix: Answer: C=1 mol.
21. Answer: B
Explanation: 1 mol gas at STP = 22.4 L.
22. Answer: C
Explanation: 2 KClO₃ → 3 O₂ → 2 moles KClO₃ produce 3/2×2=3 moles? 2 KClO₃ produce 3 moles O₂. Wait, check: 2 KClO₃ → 3 O₂ → correct: 3 moles O₂. Answer B.
23. Answer: A
Explanation: 1 mole = 6.02×10²³ particles.
24. Answer: A
Explanation: Mg:O₂=2:1 → 24 g Mg=1 mol → 0.5 mol O₂ → 0.5×32=16 g.
25. Answer: B
Explanation: 2H₂ + O₂ → 2H₂O → 3 mol H₂ require 1.5 mol O₂ → O₂ is limiting reactant.
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