Q.
Consider the reactions given below. On the basis of these reactions find out which of the algebric relations given in options (a) to (d) is correct?
(i) C(g)+4H(g)→CH4(g);ΔrH=xkJmol−1
(ii) C(graphite,s)+2H2(g)→CH4(g);ΔrH=ykJmol−1
In eqn (i), no bond is being broken while in eqn (ii), 2H−H bonds are broken. So, in eqn (ii) some of the energy is used up to break the bonds. Thus, x>y.