The Constant Pressure Specific Heat

In case of an ideal gas which is found at constant pressure would surely take up more heat in order to gain same level of temperature change and that too at constant volume. When there is constant volume heats get added up and finally help to increase temperature. At constant pressure there is some heat that would perform work.

Q = nC_PΔT

For ideal gas, it is important to apply First Law of Thermodynamics which would say that the heat is equal to:

Q = ΔE_int + W

When there is constant pressure then, W = P∆V = nR∆T

But, in case of monatomic gas, it is said ΔE_int = (3/2)nRΔT, we get:

Q = (3/2)nRΔT + nRΔT = (5/2)nRΔT

So, for a monatomic ideal gas:

C_P = (5/2)R

For diatomic and polyatomic ideal gases we get:

Di-atomic: C_P = (7/2)R

Polyatomic: C_P = 4R

Links of Previous Main Topic:-

• Statically indeterminate system
• Introduction to thermodynamics
• Statement of zeroth law of thermodynamics with explanation
• Heat and work introduction
• First law of thermodynamics for a control mass closed system undergoing a cycle
• First law of thermodynamics for a change of state for a control mass closed system
• Different types of stored energy
• The constant volume specific heat

Links of Next Mechanical Engineering Topics:-

• Specific heats of solids and liquids
• Energy of isolated system
• Perpetual motion machine of the first kind pmm 1
• Open system and control volume
• Conversion of work into heat
• Introduction to carnot cycle
• Clausius inequality entropy and irreversibility introduction