Question

29. Gaseous benzene reacts with hydrogen gas in presence
of a nickel catalyst to form gaseous cyclohexane
according to the reaction, CH 3 CH2)
A mixture of CH, and excess H, 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 CH. (by volume) present
in the original volume is
(a) 1/3 (6) 1/4 (c) 115 (d) 1/6​

Answer 1

Answer:

1/6.

Explanation:

Before the reaction is taking place the initial pressure of the C6H6 be X1 mm and for the hydrogen H2 be X2 mm. So, from the question we get that X1+X2=60.

C6H6+3H2->C6H12

So, when the reaction takes place the pressure will change as C6H6 is 0 (Since complete combustion or reaction of C6H6 takes place) and the pressure of H2 will be X2−3X1 since 3 moles of H2 react to form 1 mole of the C6H12.

 

Therefore the total pressure will be 30=X2−3X1+X1 or X2−2X1=30 mm  and also we know X1+X2=60. So solving the two equations we will get that X1 will be 10 mm, and the X2=50 mm.  

So, the fraction of the C6H6 in the original volume will be 10/60 = 1/6.