Question

Gaseous benzene reacts with hydrogen gas in presence of a nickel catalyst to form gaseous cyclohexane according to the reaction, \[ C_6H_6(g) + 3H_2(g) \xrightarrow{Ni} C_6H_{12}(g) \] A mixture of \( C_6H_6 \) and excess \( H_2 \) has a pressure of 60 mm of Hg in an unknown volume. After the gas had been passed over a nickel catalyst and all the benzene converted to cyclohexane, the pressure of the gas was 30 mm of Hg in the same volume at the same temperature. The fraction of \( C_6H_6 \) (by volume) present in the original volume is

• A. \( \frac{1}{3} \)
• B. \( \frac{1}{5} \)
• C. \( \frac{1}{6} \)
• D. \( \frac{1}{4} \)

Hint:

The fraction of a gas present in a reaction can be determined using the change in pressure, since the volume of the gas is directly proportional to the pressure in a constant volume system.

Answer 1

The Correct Option is A

Using the ideal gas law and the mole ratios from the balanced equation, we calculate the volume fraction of \( C_6H_6 \) before the reaction as \( \frac{1}{3} \), based on the change in pressure before and after the reaction.