Answer to Question #95717 in General Chemistry for Sarah Alruwaili

Question

14.60g sample of an unknown compound, composed only of carbon, hydrogen, and oxygen, produced 28.6g of CO2 and 14.6g of H2O in a combustion analysis. What is the mass percent composition of oxygen of the unknown compound?

Answer 1

Mass of carbon +mass of hydrogen+mass of oxygen = 14.6$\ \ \ \ \ \ ........(1)$

$Mass\ of\ C\ in\ CO_2=\frac{12}{44}\times 28.6=7.8\ g$

$Mass\ of\ H\ in \ H_2O=\frac{2}{18}\times14.6=1.6222\ g$

these carbon and hydrogen came only from the unknown sample

So,

Mass of oxygen in unknown sample = $14.6-7.8-1.6222=5.1778\ g$

Percentage composition of oxygen in sample = $\frac{5.1778}{14.6}\times 100=35.464\%$