Question

Assertion : Enthalpy of graphite is lower than that of diamond.

Reason: Entropy of graphite is greater than that of diamond

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

Correct option  (b) Both A and R are true but R is not correct explanation of A

Explanation:

Greater entropy of graphite is related to its structure as graphite is less compact and rigid than diamond. ΔH^o_f for graphite is zero, but the ΔH^o_f  for diamond is 2 kJ/mol. That is because graphite is the standard state of carbon, not diamond.