Question

At constant pressure, the heat of formation of a compound is not dependent on temperature, when:
(A) $\Delta {{C}_{P}} =0$
(B) $\Delta {{C}_{v}} =0$
(C) $\Delta {{C}_{p}}>0$
(D) $\Delta {{C}_{p}} <0$

Answer 1

The standard enthalpy of formation or standard heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states.

Complete step by step solution:
We have been asked that at constant pressure, the heat of formation of a compound is not dependent on temperature,
For which we need to tell the conditions,
So, firstly: Enthalpy is a property of a thermodynamic system, that is a convenient state function preferred in many measurements in chemical, biological, and physical systems at a constant pressure. It is defined as the sum of the system's internal energy and the product of its pressure and volume
As we know, the heat of formation of a compound is the change of enthalpy during the formation of 1 mole of the substance from its constituent elements, with all substances in their standard states.
So, using the formula of enthalpy:
$\Delta H=\Delta {{C}_{P}} T$
So, if $\Delta {{C}_{p}} =0$,
Then $\Delta H=0$,
This is how the heat of formation of a compound becomes independent of temperature.

Therefore, we can conclude that option (A) is correct.

Note: Standard Enthalpies of Formation. The magnitude of enthalpy for a reaction depends on the physical states of the reactants and the products (gas, liquid, solid, or solution), the pressure of any gases present, and the temperature at which the reaction is carried out.