Questions on Combination Reactions
Multiple-Choice Questions: Combination Reactions
1. What is a combination reaction?
A) A reaction where one reactant splits into two products
B) A reaction between acids and bases
C) A reaction where two or more substances form one product
D) A reaction that involves oxygen only
E) A reversible reaction only
2. Which of the following is a combination reaction?
A) H₂O → H₂ + O₂
B) Na + Cl₂ → NaCl
C) HCl + NaOH → NaCl + H₂O
D) CaCO₃ → CaO + CO₂
E) Zn + HCl → ZnCl₂ + H₂
3. Which equation correctly shows a combination reaction?
A) 2H₂ + O₂ → 2H₂O
B) 2KClO₃ → 2KCl + 3O₂
C) CaCO₃ → CaO + CO₂
D) H₂O → H₂ + O₂
E) NaOH + HCl → NaCl + H₂O
4. Which of the following is not a combination reaction?
A) Fe + S → FeS
B) 2Na + Cl₂ → 2NaCl
C) N₂ + 3H₂ → 2NH₃
D) 2KClO₃ → 2KCl + 3O₂
E) C + O₂ → CO₂
5. Which best describes the product of a combination reaction?
A) Two or more products
B) A single compound
C) Always a gas
D) Only elements
E) Only acids
6. In a combination reaction, which type of substances can be reactants?
A) Only elements
B) Only compounds
C) Only metals
D) Elements and/or compounds
E) Only nonmetals
7. Which balanced equation represents the synthesis of water?
A) H₂O → H₂ + O₂
B) H₂ + O₂ → H₂O
C) 2H₂ + O₂ → 2H₂O
D) H₂ + O → H₂O₂
E) H₂O₂ → H₂O + O₂
8. What is formed in the combination reaction: 2Mg + O₂ → ?
A) MgO
B) Mg₂O
C) MgO₂
D) Mg₂O₃
E) MgO₃
9. Which is a typical example of a metal oxide synthesis reaction?
A) Mg + O₂ → MgO
B) Zn + CuSO₄ → ZnSO₄ + Cu
C) H₂O → H₂ + O₂
D) NaOH + HCl → NaCl + H₂O
E) KClO₃ → KCl + O₂
10. What type of chemical reaction is represented by: N₂ + 3H₂ → 2NH₃?
A) Decomposition
B) Single replacement
C) Combination
D) Combustion
E) Neutralization
11. What is the product of Ca + O₂ in a combination reaction?
A) CaO
B) Ca₂O₃
C) Ca₂O
D) CaO₂
E) CaO₃
12. Which of the following represents the formation of a binary compound in a combination reaction?
A) HCl + NaOH → NaCl + H₂O
B) 2Na + Cl₂ → 2NaCl
C) H₂O₂ → H₂O + O₂
D) NaHCO₃ → Na₂CO₃ + CO₂ + H₂O
E) KClO₃ → KCl + O₂
13. The reaction of iron and oxygen to form iron(III) oxide is:
A) 4Fe + 3O₂ → 2Fe₂O₃
B) Fe + O₂ → FeO
C) Fe₂O₃ → Fe + O₂
D) Fe + O → Fe₂O₃
E) 2FeO → Fe + O₂
14. What is the correct name for a reaction where multiple reactants form one product?
A) Displacement
B) Decomposition
C) Combination
D) Double replacement
E) Ionization
15. Which is a synthesis reaction involving nonmetals?
A) C + O₂ → CO₂
B) Na + H₂O → NaOH + H₂
C) CaCO₃ → CaO + CO₂
D) H₂O → H₂ + O₂
E) Cu + AgNO₃ → Cu(NO₃)₂ + Ag
16. In the synthesis reaction: SO₃ + H₂O → ?
A) H₂SO₃
B) H₂SO₄
C) SO₂
D) HSO₃
E) H₂S
17. A combination reaction can also be called:
A) Redox reaction
B) Synthesis reaction
C) Neutralization
D) Decomposition
E) Double-displacement
18. Which is a characteristic of combination reactions?
A) Many products form
B) Only involve ionic compounds
C) One single product is formed
D) Only occur with metals
E) Always absorb energy
19. What product is formed in the synthesis reaction: CO + O₂ → ?
A) CO₂
B) C₂O
C) CO₃
D) O₃
E) C₂O₃
20. What is the balanced equation for: S + O₂ → ?
A) S + O₂ → SO₃
B) 2S + 3O₂ → 2SO₃
C) S + O₂ → SO₂
D) 2S + O₂ → 2SO₂
E) S + 2O₂ → SO₄
Answer Key with Explanations
1. C – A combination reaction combines substances to form one product.
2. B – Na + Cl₂ → NaCl is a classic combination reaction.
3. A – 2H₂ + O₂ → 2H₂O is a synthesis reaction forming water.
4. D – 2KClO₃ → 2KCl + 3O₂ is a decomposition reaction.
5. B – The hallmark of combination reactions is a single compound as product.
6. D – Reactants can be elements and/or compounds.
7. C – Balanced synthesis of water: 2H₂ + O₂ → 2H₂O.
8. A – Magnesium and oxygen form MgO.
9. A – Metal (Mg) + Oxygen → Metal oxide (MgO).
10. C – Two substances form one product: a combination reaction.
11. A – Ca + O₂ → CaO is a synthesis reaction.
12. B – Na + Cl₂ → NaCl forms a binary compound.
13. A – Correct balanced form for iron(III) oxide formation.
14. C – Another name for a combination reaction is synthesis.
15. A – Nonmetal + nonmetal: C + O₂ → CO₂.
16. B – SO₃ + H₂O → H₂SO₄ is a synthesis of sulfuric acid.
17. B – Combination and synthesis are synonyms.
18. C – Always results in one product.
19. A – CO + O₂ → CO₂ is a synthesis reaction.
20. C – S + O₂ → SO₂ is balanced and typical.
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