Q. Gaseous benzene reacts with hydrogen gas in presence of a nickel catalyst to form gaseous cyclohexane according to the reaction,

A mixture of and excess has a pressure of of 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 of in the same volume at the same temperature. The fraction of (by volume) present in the original volume is

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Solution:

Suppose initially, pressure of mmand that of
mm ..... (i)
After the reaction,
Pressure of (as all has reacted)
Pressure of
Pressure of
Total pressure
or,
Solving (i) and (ii), we get

Fraction of by volume fraction of moles
fraction of pressure