JEE Main · 2025 · 08 Apr 2025 · Shift 2 · Some Basic Concepts of Chemistry

In combustion analysis all the hydrogen of the compound ends up as water and all the carbon as carbon dioxide. The mass of hydrogen is $\frac{2}{18}\times 0.127=0.0141\text{g}$, so the hydrogen content is $\frac{0.0141}{0.210}\times 100=6.72\%$. The mass of carbon is $\frac{12}{44}\times 0.307=0.0837\text{g}$, and oxygen is found by difference, $0.210-0.0837-0.0141=0.1122\text{g}$, giving an oxygen content of $\frac{0.1122}{0.210}\times 100=53.41\%$. The compound contains 6.72 percent hydrogen and 53.41 percent oxygen.