Question

10 mL of gaseous hydrocarbon on combustion gives 40 mL of CO\(_2\)(g) and 50 mL of water vapour. The total number of carbon and hydrogen atoms in the hydrocarbon is ______ .

Answer 1

Correct Answer: 14

The formula of the hydrocarbon is \( \text{C}_x\text{H}_y \). The complete combustion reaction is: \[\text{C}_x\text{H}_y + \left(x + \frac{y}{4}\right) \text{O}_2 \rightarrow x \text{CO}_2 + \frac{y}{2} \text{H}_2\text{O}\] Given: 10 mL of hydrocarbon yields 40 mL of \(\text{CO}_2\) and 50 mL of water vapor (\(\text{H}_2\text{O}\)). From the stoichiometry: For \( \text{CO}_2 \): \(x \times 10 \, \text{mL} = 40 \, \text{mL} \implies x = 4\) For \(\text{H}_2\text{O}\): \(\frac{y}{2} \times 10 \, \text{mL} = 50 \, \text{mL} \implies y = 10\) The hydrocarbon is \( \text{C}_4\text{H}_{10} \). The total number of carbon and hydrogen atoms is \( x + y = 4 + 10 = 14 \). Conclusion: The hydrocarbon contains a total of 14 carbon and hydrogen atoms.