Gaseous benzene reacts with hydrogen gas in presence of a nickel catalyst to form gaseous cyclohexane according to the reaction C 6 H 6 g + 3 H 2 g → C 6 H 12 g A mixture of C 6 H 6 and excess H 2 has

Question

Gaseous benzene reacts with hydrogen gas in presence of a nickel catalyst to form gaseous cyclohexane according to the reaction
$C_{6} H_{6 (g)} + 3 H_{2 (g)} \to C_{6} H_{12 (g)}$
A mixture of $C_{6} H_{6}$ and excess $H_{2}$ has a pressure of 60 mm of Hg in an unknown volume. After the gas has 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 and temperature. The fraction of $C_{6} H_{6}$ (by volume) present in the original volume is 1/y. The value of 'y' is

TestHub · Accepted Answer

Suppose initially, pressure of C 6 H 6 g = P 1 mm and that of H 2 g = P 2 mm. So P 1 + P 2 = 60 mm …(i) After the reaction Pressure of C 6 H 6 g = 0 Pressure of H 2 g = P 2 - 3 P 1 Pressure of C 6 H 12 g = P 1 Total pressure = P 2 - 3 P 1 + P 1 = 30 mm Or P 2 - 2 P 1 = 30 mm …(ii) Solving (i) and (ii) we get P 1 = 10 mm P 2 = 50 mm Fraction of C 6 H 6 g by volume = Fraction of moles = Fraction of pressures = 10 60 = 1 6

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