Questions on Limiting Reactant
Multiple-Choice Questions – Limiting Reactant
1. Which reactant limits the reaction if 4 mol H₂ reacts with 2 mol O₂?
H₂ + ½ O₂ → H₂O
A) H₂
B) O₂
C) H₂O
D) Both are limiting
E) Cannot be determined
2. If 10 mol of A reacts with 6 mol of B in the reaction: A + 2B → C, which is the limiting reactant?
A) A
B) B
C) C
D) Both
E) Cannot be determined
3. In the reaction N₂ + 3H₂ → 2NH₃, if 5 mol N₂ and 9 mol H₂ are present, the limiting reactant is:
A) N₂
B) H₂
C) NH₃
D) Both
E) Cannot be determined
4. What is the limiting reactant when 4 mol Fe reacts with 3 mol O₂?
4Fe + 3O₂ → 2Fe₂O₃
A) Fe
B) O₂
C) Fe₂O₃
D) None
E) Equal amounts
5. In the reaction 2H₂ + O₂ → 2H₂O, 3 mol H₂ and 2 mol O₂ are mixed. Which is limiting?
A) H₂
B) O₂
C) H₂O
D) Neither
E) Not enough information
6. 10 g of Al reacts with 20 g of Cl₂. Which is limiting?
2Al + 3Cl₂ → 2AlCl₃
A) Al
B) Cl₂
C) AlCl₃
D) None
E) Not enough data
7. 8 g of CH₄ and 32 g of O₂ are reacted. CH₄ + 2O₂ → CO₂ + 2H₂O. Limiting reactant?
A) CH₄
B) O₂
C) CO₂
D) H₂O
E) Both
8. Which substance is limiting when 5 mol Na reacts with 3 mol Cl₂?
2Na + Cl₂ → 2NaCl
A) Na
B) Cl₂
C) NaCl
D) Neither
E) Not enough info
9. For the reaction C + O₂ → CO₂, if 12 g of C reacts with 32 g of O₂, which is limiting?
A) C
B) O₂
C) CO₂
D) Both
E) Cannot tell
10. In 2K + Cl₂ → 2KCl, what is the limiting reactant when 0.5 mol K reacts with 0.5 mol Cl₂?
A) K
B) Cl₂
C) KCl
D) Both
E) Not enough data
11. In the reaction Zn + 2HCl → ZnCl₂ + H₂, if 3 mol Zn and 2 mol HCl are available, limiting reactant is:
A) Zn
B) HCl
C) H₂
D) ZnCl₂
E) Not determinable
12. 2 mol of A reacts with 1 mol of B in the reaction 3A + 2B → C. Limiting reactant?
A) A
B) B
C) C
D) Equal
E) Can't determine
13. 1 mol of NaOH reacts with 1 mol of H₂SO₄. 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
A) NaOH
B) H₂SO₄
C) H₂O
D) Na₂SO₄
E) None
14. Which is the limiting reactant when 2 mol Ca reacts with 3 mol HCl?
Ca + 2HCl → CaCl₂ + H₂
A) Ca
B) HCl
C) H₂
D) CaCl₂
E) Not enough data
15. If 6 g of H₂ reacts with 96 g of O₂, which is limiting?
2H₂ + O₂ → 2H₂O
A) H₂
B) O₂
C) H₂O
D) Both
E) Need moles
16. For the reaction 2H₂ + O₂ → 2H₂O, 1 mol H₂ and 1 mol O₂ are used. Limiting reactant?
A) H₂
B) O₂
C) H₂O
D) Equal
E) Cannot say
17. In 2Fe + 3Cl₂ → 2FeCl₃, what is limiting if 5 mol Fe and 5 mol Cl₂ react?
A) Fe
B) Cl₂
C) FeCl₃
D) Both
E) No limiting
18. Which reactant is limiting when 4 mol CO reacts with 2 mol O₂?
2CO + O₂ → 2CO₂
A) CO
B) O₂
C) CO₂
D) Both
E) Cannot tell
19. In the reaction 3H₂ + N₂ → 2NH₃, what limits if 6 mol H₂ and 4 mol N₂ are present?
A) H₂
B) N₂
C) NH₃
D) Both
E) Data insufficient
20. 4 mol A reacts with 6 mol B in: A + 3B → AB₃. Limiting reactant?
A) A
B) B
C) AB₃
D) Both
E) Can't determine
21. 20 g Mg and 60 g HCl are mixed. Mg + 2HCl → MgCl₂ + H₂. Which is limiting?
A) Mg
B) HCl
C) H₂
D) Equal
E) Not enough info
22. In 2Al + 3Cl₂ → 2AlCl₃, 5 mol Al and 7 mol Cl₂ are available. Limiting reactant?
A) Al
B) Cl₂
C) AlCl₃
D) Both
E) Can't determine
23. 10 g of Ca reacts with 20 g of Br₂. Ca + Br₂ → CaBr₂. Limiting reactant?
A) Ca
B) Br₂
C) CaBr₂
D) Neither
E) Can't tell
24. In 2Na + H₂ → 2NaH, if 4 mol Na and 1 mol H₂ are present, which is limiting?
A) Na
B) H₂
C) NaH
D) Both
E) Can't determine
25. 2SO₂ + O₂ → 2SO₃. 4 mol SO₂ and 2 mol O₂ are used. Limiting reactant?
A) SO₂
B) O₂
C) SO₃
D) Neither
E) Equal
26. 2K + Br₂ → 2KBr. 10 g K and 80 g Br₂. Which is limiting?
A) K
B) Br₂
C) KBr
D) Neither
E) Insufficient data
27. Ca + 2H₂O → Ca(OH)₂ + H₂. 40 g Ca and 36 g H₂O. Limiting?
A) Ca
B) H₂O
C) Ca(OH)₂
D) H₂
E) Equal
28. 2Na + Cl₂ → 2NaCl, with 23 g Na and 70.9 g Cl₂. Limiting reactant?
A) Na
B) Cl₂
C) NaCl
D) Neither
E) Can't say
29. CH₄ + 2O₂ → CO₂ + 2H₂O, with 16 g CH₄ and 48 g O₂. Limiting reactant?
A) CH₄
B) O₂
C) CO₂
D) H₂O
E) Equal
30. C₂H₆ + 3O₂ → 2CO₂ + 3H₂O, with 30 g C₂H₆ and 96 g O₂. Limiting?
A) C₂H₆
B) O₂
C) CO₂
D) H₂O
E) Not enough info
- Questions on Mass–Mass Stoichiometry
- Questions on Volume-Volume Stoichiometry
- Questions on Mass-Volume Stoichiometry
Answers and Explanations:
1. B – 4 mol H₂ needs 2 mol O₂, but 2 mol O₂ is exact → no excess → O₂ limits.
2. B – 10 A: needs 20 B, but only 6 → B is limiting.
3. B – 5 mol N₂ needs 15 mol H₂, but only 9 → H₂ limits.
4. A – 4 mol Fe: needs 3 mol O₂; you have exact match, but balanced for 4:3 → Fe limiting.
5. A – 3 mol H₂ needs 1.5 mol O₂, you have 2 → excess → H₂ is limiting.
6. A – 10 g Al = ~0.37 mol; 20 g Cl₂ = ~0.28 mol → Cl₂ needed = (3/2) × 0.37 ≈ 0.56 mol → not enough → Cl₂ is limiting.
7. B – 8 g CH₄ = 0.5 mol; 32 g O₂ = 1 mol → need 1 mol O₂ → exact → no limiting, but slight excess = CH₄ limiting.
8. A – 5 mol Na needs 2.5 mol Cl₂; you have 3 → Na is limiting.
9. B – 12 g C = 1 mol; 32 g O₂ = 1 mol → reaction is 1:1 → no limiting.
10. A – 0.5 mol K: needs 0.25 mol Cl₂ → 0.5 mol Cl₂ present → K is limiting.
11. B – 3 mol Zn needs 6 mol HCl → only 2 mol HCl → HCl limits.
12. A – 2 A needs 4 B; only 1 B present → B is limiting.
13. A – 1 mol NaOH needs 0.5 mol H₂SO₄ → 1 mol present → NaOH limiting.
14. B – 2 mol Ca needs 4 mol HCl → only 3 → HCl is limiting.
15. B – 6 g H₂ = 3 mol; 96 g O₂ = 3 mol → 3 mol H₂ needs 1.5 mol O₂ → O₂ in excess, so H₂ is limiting.
16. A – 1 mol H₂ needs 0.5 mol O₂ → 1 mol present → H₂ limits.
17. B – 5 mol Fe needs 7.5 mol Cl₂ → only 5 → Cl₂ limiting.
18. B – 4 mol CO needs 2 mol O₂ → 2 mol is exact → no limiting, but O₂ consumed fully.
19. A – 6 mol H₂ needs 2 mol N₂ → 4 mol present → H₂ limiting.
20. B – 4 mol A needs 12 mol B → only 6 → B limiting.
21. A – 20 g Mg = 0.82 mol; 60 g HCl = 1.64 mol → needs 2 × 0.82 = 1.64 mol → both exact, but Mg limits first.
22. B – 5 mol Al needs 7.5 mol Cl₂ → only 7 → Cl₂ limiting.
23. A – 10 g Ca = 0.25 mol; 20 g Br₂ = 0.125 mol → Br₂ limiting.
24. B – 4 mol Na needs 2 mol H₂ → only 1 mol → H₂ limiting.
25. A – 4 mol SO₂ needs 2 mol O₂ → exact → SO₂ limiting.
26. A – 10 g K = 0.26 mol; 80 g Br₂ = 0.5 mol → need 0.26 mol Br₂ → K limiting.
27. B – 40 g Ca = 1 mol; 36 g H₂O = 2 mol → need 2 mol H₂O → exact → H₂O limiting.
28. A – 23 g Na = 1 mol; 70.9 g Cl₂ = 1 mol → needs 0.5 mol Cl₂ → Na limiting.
29. B – 16 g CH₄ = 1 mol; 48 g O₂ = 1.5 mol → needs 2 mol O₂ → O₂ limiting.
30. B – 30 g C₂H₆ = 1 mol; 96 g O₂ = 3 mol → needs 3 mol O₂ → equal → but O₂ fully consumed, so O₂ limiting.
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