Question

0.2 g of an organic compound containing C, H, and O on complete combustion gave 0.46 g of \(CO_2\) and 0.25 g of \(H_2O\). What is the percentage of oxygen in that compound? 

• A. 23.4
• B. 26.7
• C. 46.8
• D. 36.2

Hint:

When solving for the composition of compounds from combustion data, ensure to convert the mass of combustion products back to the mass of the original elements using their molar ratios.

Answer 1

The Correct Option is A

To find the percentage of oxygen in the compound, we first calculate the mass of carbon and hydrogen in the compound from the combustion products.
- From \(CO_2\): \(0.46 \, g\) of \(CO_2\) contains \(0.46 \times \frac{12}{44} = 0.125 \, g\) of carbon.
- From \(H_2O\): \(0.25 \, g\) of \(H_2O\) contains \(0.25 \times \frac{2}{18} = 0.0278 \, g\) of hydrogen.
The total mass of carbon and hydrogen is \(0.125 + 0.0278 = 0.1528 \, g\).
The mass of oxygen in the compound is the total mass minus the mass of carbon and hydrogen:
\[ 0.2 \, g - 0.1528 \, g = 0.0472 \, g \]
The percentage of oxygen in the compound is:
\[ \frac{0.0472}{0.2} \times 100 = 23.6\% \]
Thus, rounding to the nearest given option, the percentage of oxygen is approximately \(23.4\%\).