MCQ practice · SSC Chemistry Board questions · Chapter 6: Concept of Mole and Chemical Counting
How many grams of NH₃ will form in the stimulus reaction?
Think it through first, then pick an option.
- a 12.75 grams
- b 18 grams
- c 22.67 grams
- d 34 grams
Answer and explanation
Correct answer: c 22.67 grams
N₂ = 21/28 = 0.75 mole, H₂ = 4/2 = 2 moles; moles ÷ coefficient: N₂ 0.75, H₂ 0.67, so H₂ is limiting; NH₃ = 2 × 2/3 = 1.333 mole × 17 = 22.67 g.
Why the other options are wrong
- a 12.75 grams: 12.75 g is a slip; H₂ is limiting, and 2 moles of H₂ give 4/3 mole of NH₃ = 22.67 g.
- b 18 grams: 18 g does not fit the working; the answer is 22.67 g.
- d 34 grams: 34 g would need 1 full mole of N₂ to react; here H₂ is limiting, giving 22.67 g.
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