# An organic compound contains 69% carbon and 4.8% hydrogen, the remainder being oxygen.

Question:

An organic compound contains 69% carbon and 4.8% hydrogen, the remainder being oxygen. Calculate the masses of carbon dioxide and water produced when 0.20 g of this substance is subjected to complete combustion.

Solution:

Percentage of carbon in organic compound = 69 %

That is, 100 g of organic compound contains 69 g of carbon.

$\therefore 0.2 \mathrm{~g}$ of organic compound will contain $=\frac{69 \times 0.2}{100}=0.138 \mathrm{~g}$ of $\mathrm{C}$

Molecular mass of carbon dioxide, $\mathrm{CO}_{2}=44 \mathrm{~g}$

That is, $12 \mathrm{~g}$ of carbon is contained in $44 \mathrm{~g}$ of $\mathrm{CO}_{2}$.

Therefore, $0.138 \mathrm{~g}$ of carbon will be contained in $\frac{44 \times 0.138}{12}=0.506 \mathrm{~g}$ of $\mathrm{CO}_{2}$

Thus, $0.506 \mathrm{~g}$ of $\mathrm{CO}_{2}$ will be produced on complete combustion of $0.2 \mathrm{~g}$ of organic compound.

Percentage of hydrogen in organic compound is 4.8.

i.e., 100 g of organic compound contains 4.8 g of hydrogen.

Therefore, $0.2 \mathrm{~g}$ of organic compound will contain $\frac{4.8 \times 0.2}{100}=0.0096 \mathrm{~g}$ of $\mathrm{H}$

It is known that molecular mass of water $\left(\mathrm{H}_{2} \mathrm{O}\right)$ is $18 \mathrm{~g}$.

Thus, $2 \mathrm{~g}$ of hydrogen is contained in $18 \mathrm{~g}$ of water.

$\therefore 0.0096 \mathrm{~g}$ of hydrogen will be contained in $\frac{18 \times 0.0096}{2}=0.0864 \mathrm{~g}$ of water

Thus, $0.0864 \mathrm{~g}$ of water will be produced on complete combustion of $0.2 \mathrm{~g}$ of the organic compound.