Question

Which of the following statements is/are correct?

1. ∆H° for the reaction C(diamond) + O2(g) → CO2(g) is the enthalpy of combustion of diamond.

2. ∆H° for the reaction C(graphite) + 1/2 O2(g) → CO(g) is the standard enthalpy of formation (∆Hf) of CO(g).

3. ∆H° for the reaction C(graphite) → C(diamond) is the standard enthalpy of formation (∆Hf) of diamond.

A. all

B. 2 only

C. 1 and 2 only

D. 1 and 3 only

E. 2 and 3 only

Answer 1

Solution:

The correct statements are-

1. ∆H° for the reaction C(diamond) + O2(g) → CO2(g) is the enthalpy of combustion of diamond.

" The enthalpy of combustion  is the heat energy released when one mole of a substance burns completely in oxygen".

2. ∆H° for the reaction C(graphite) + 1/2 O2(g) → CO(g) is the standard enthalpy of formation (∆Hf) of CO(g).

" The standard enthalpy of formation is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements".

hence, option C is correct.