When a mixture of benzene and excess H2 gas having pressure 60 mm of Hg was passed over nickel catalyst, cyclohexane was formed as follows:C6H6(g)+3H2(g)⟶NiC6H12(g) The pressure was now observed to be 30 mm of Hg in the same volume at the same temperature. How much fraction of benzene by volume was present in the original mixture

C6H6(g)+3H2(g)→Ni  C6H12(g)  I mole     3 mole   Initial state : PC6H6 + PH2 =60 mm P1+ P2 = 60 mm......(A)   After completion of reaction    Pressure due to C6H6(g)=0∴ Pressure due to H2(g)=P2−3P1 Pressure of due to C6H12(g)=P1Total pressure due to H2 and C6H12(g) =P2−3P1+P1=P2−2P1  P2−2P1= 30mm.....(B) Subtracting equation (B) from equation (A), we get:P1+P2−P2+2P1= 60−30=30mm;  3P1=30mm∴ P1=10mmHence fraction of C6H6 by volume means fraction of its moles or fraction of pressure =1060=0.167=0.17