Question

Please explain how to solve this: when cp=20J/kg k and 1mole of gas is present then cv is ? a:2.36J/kg k b:3.36J/kg k c:4.36J/kg k d:5.36J/kg k (please explain the solution)​

Answer 1

Answer:

You'd need the molar mass of the gas as the specific heat is defined in mass and not in moles

Check the attachment for reference

Answer 2

Given :

Heat capacity at constant pressure ($C_{p}$) = 20 J. mol⁻¹. K⁻¹

To Find :

Heat capacity at constant volume ($C_v$)

Solution :

We know, for an ideal gas, the difference between between the molar heat capacities at constant pressure and volume is equal to the universal gas constant (R).

Thus,  

         $C_{p}$  -  $C_v$ = R

⇒        20  -   C$_v$ = 8.314

⇒                   C$_v$ = 20 - 8.314

∴                    C$_v$ = 11.686 J. mol⁻¹. K⁻¹

Therefore, the value of C$_v$ is 11.686 J. mol⁻¹. K⁻¹

Note : The given options are incorrect and the unit of C$_p$ mentioned in the question was also incorrect.