Q. Mass % of carbon in ethanol is

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A

52

B

13

C

34

D

90

Solution:

Ethanol is $C_{2}H_{5}OH$
Molecular mass $=12\times 2+6\times 1+16\times 1$
$=24+6+16=46$
Mass of carbon in ethanol $=12\times 2=24$
$\text{Mass} \, \text{\%} \, \text{of} \, \text{carbon} \, \text{=} \, \frac{\text{Mass} \, \text{of} \, \text{carbon}}{\text{Molar} \, \text{mass} \, \text{of} \, \text{compound}} \, \text{\times } \, \text{100}$
$=\frac{24}{46}\times 100=52\%$

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