Question

One mole of a hydrocarbon, on combustion in air, produces two moles of \( \text{CO}_2 \), two moles of \( \text{H}_2\text{O} \), and a large amount of heat. This hydrocarbon is:

• A. ethyne
• B. ethene
• C. ethane
• D. methane

Answer 1

The Correct Option is C

Step 1: Understanding Combustion:
Hydrocarbon combustion reacts the hydrocarbon with atmospheric oxygen, yielding carbon dioxide (\( \text{CO}_2 \)) and water (\( \text{H}_2\text{O} \)), while releasing significant heat. The general reaction is:
\[ \text{Hydrocarbon} + O_2 \rightarrow CO_2 + H_2O + \text{heat} \]

Step 2: Data Analysis:
The problem states that one mole of hydrocarbon yields two moles of \( \text{CO}_2 \) and two moles of \( \text{H}_2\text{O} \). This implies a balanced equation with 2 moles of carbon and 4 moles of hydrogen, characteristic of a simple alkane.

Step 3: Hydrocarbon Identification:
The stoichiometry (2 moles \( \text{CO}_2 \) and 2 moles \( \text{H}_2\text{O} \)) indicates the hydrocarbon is \( \text{C}_2\text{H}_6 \), known as ethane.

Step 4: Ethane Combustion Equation:
The combustion of ethane is represented as:
\[ \text{C}_2\text{H}_6 + 3 \text{O}_2 \rightarrow 2 \text{CO}_2 + 3 \text{H}_2\text{O} + \text{heat} \] This equation shows one mole of ethane producing two moles of \( \text{CO}_2 \) and three moles of \( \text{H}_2\text{O} \), matching the provided stoichiometric information.

Conclusion:
The hydrocarbon is ethane (\( \text{C}_2\text{H}_6 \)), which produces two moles of \( \text{CO}_2 \) and two moles of \( \text{H}_2\text{O} \) upon combustion. This is a highly exothermic reaction.