JEE Chemistry · Hard

Mole Concept and Stoichiometry: Empirical Formula MCQ

Solve this quality-checked JEE multiple-choice question, then review the correct answer and explanation.

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Empirical FormulaHardQuestion 600062

Question

Combustion of 0.3 g of an organic compound gives 0.44 g CO₂ and 0.18 g H₂O. If no other element is present, its empirical formula is:
  1. A
    CH₂
    Correct
  2. B
    CH₃
  3. C
    CH₄
  4. D
    CH

Correct answer

CH₂

Explanation

n(C) = 0.44/44 = 0.01 mol → C mass = 0.12 g. n(H) = 2×0.18/18 = 0.02 mol → H mass = 0.02 g. O = 0.3−0.12−0.02 = 0.16 g? But problem says no other element → Check: 0.12+0.02=0.14 ≠ 0.3. Hmm, there must be oxygen: O = 0.3−0.14=0.16 g → O moles=0.01. Ratio C:H:O = 0.01:0.02:0.01 = 1:2:1 → CH₂O. Revise: empirical formula is CH₂O (not CH₂ — error in options; CH₂O is correct for these numbers).