WAEC Chemistry 2012 Objective — Question 44

Question 44 of 50 from the West African Examinations Council (WAEC) Chemistry 2012 Objective paper, with the correct answer and a full explanation.

A compound contains 40.0% C, 6.7% H and 53.3% O. If the molecular mass of the compound is 180, its molecular formula is [C=12, H=1, O=16]

A. CH2O
B. C3H6O3
C. C6H6O3
D. C6H12O6Correct

Explanation

Empirical formula from percentages (40.0/12 : 6.7/1 : 53.3/16 ≈ 1:2:1) gives CH2O (empirical mass 30). Since molecular mass is 180, n=180/30=6, so molecular formula = C6H12O6.

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