MCQ practice · SSC Chemistry Board questions · Chapter 6: Concept of Mole and Chemical Counting
What is the mass ratio of oxygen to hydrogen in the reactants?
Think it through first, then pick an option.
- a 1 : 8
- b 8 : 1
- c 1 : 16
- d 16 : 1
Answer and explanation
Correct answer: b 8 : 1
Balanced 2H₂ + O₂ → 2H₂O: O₂ = 32 g and H₂ = 4 g, so 8 : 1.
Why the other options are wrong
- a 1 : 8: The ratio is written backwards; in 2H₂ + O₂, O₂ : H₂ = 32 : 4 = 8 : 1.
- c 1 : 16: 1 : 16 is backwards and unbalanced; the balanced equation gives O : H = 8 : 1.
- d 16 : 1: 16 : 1 comes from not balancing (32 : 2); balanced, there are two H₂, so 8 : 1.
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