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WAEC Chemistry 2015 Paper

Question : 39

Total: 50

[H = 1.00, C = 12.0, O = 16.0]

Solution:

Concept:

The molecular formula is a whole-number multiple of the empirical formula.

Explanation:

Let the molecular formula be

( \mathrm{CH_2O} )_n

Its molecular mass is

n \times [12 + (2 \times 1) + 16] = 90

So,

n \times 30 = 90

Thus,

n = \frac{90}{30} = 3

Therefore, the molecular formula is

( \mathrm{CH_2O} )_3 = \mathrm{C_3H_6O_3}

Answer:

\mathrm{C_3H_6O_3}

(Option C).

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