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WAEC Chemistry 2017 Paper

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Question : 28

Total: 50

A hydrocarbon contained 14.3% hydrogen. The empirical formula for the hydrocarbon is [H= 1.0, C= 12.0]

$\mathrm{CH}$
$\mathrm{CH}_2$
$\mathrm{CH}_3$
$\mathrm{CH}_4$

Solution:

The percentage of Carbon in the compound is (100 - 14.3)% = 85.7%

C : H

$\frac{85.7}{12.0} : \frac{14.3}{1.0}$

$7.14 : 14.3$

$\frac{7.14}{7.14} : \frac{14.3}{7.14}$

$\approx\text{eq}\,1 : 2$

Therefore, the empirical formula is $\mathrm{CH}_2$ .

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