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Question

Chemistry Question on Hydrocarbons

10 mL of gaseous hydrocarbon on combustion gives 40 mL of CO2_2(g) and 50 mL of water vapour. The total number of carbon and hydrogen atoms in the hydrocarbon is ______ .

Answer

Let the formula of the hydrocarbon be CxHy\text{C}_x\text{H}_y. On complete combustion, the reaction can be represented as:
CxHy+(x+y4)O2xCO2+y2H2O\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}
Step-by-step Calculation:
According to the given data, 10 mL of hydrocarbon produces 40 mL of CO2\text{CO}_2 and 50 mL of water vapor (H2O\text{H}_2\text{O}).
From the stoichiometry of the reaction:
x×10mL=40mL    x=4x \times 10 \, \text{mL} = 40 \, \text{mL} \implies x = 4
Similarly, for water:
y2×10mL=50mL    y=10\frac{y}{2} \times 10 \, \text{mL} = 50 \, \text{mL} \implies y = 10
Therefore, the hydrocarbon is C4H10\text{C}_4\text{H}_{10}.
Total number of carbon and hydrogen atoms:
Total atoms=x+y=4+10=14\text{Total atoms} = x + y = 4 + 10 = 14
Conclusion: The total number of carbon and hydrogen atoms in the hydrocarbon is 14.