Question

Complete combustion of $750\text{g}$ of an organic compound provides $420\text{g}$ of $C{O}_2$ and $210\text{g}$ of $H_{2}O$. The percentage (by mass) composition of carbon and hydrogen in organic compound is $15.3$ and ____ respectively. (Round off to the Nearest Integer).

• A. 3.0
• B. 3
• C. 3.00

Answer 1

Answer: (A), (B), (C)

$44\text{g}C{O}_2$ has $12\text{g}$ carbon
$\Rightarrow 420\text{g}C{O}_2\text{has}=\frac{12}{44}\times 420=114.545\text{g}\text{Carbon}$
$\%$ of carbon:
$\frac{114.545}{750}\times 100=15.3\%$

$18\text{g}{H}_{2}O$ has $2\text{g}{H}_2$
$\Rightarrow 210\text{g}{H}_{2}O\text{has}\frac{2}{18}\times 210=23.33\text{g}\text{Hydrogen}$
$\%$ of hydrogen:
$\frac{23.33}{750}\times 100=3.11\%\approx 3\%$