Question

A quantity of heat ‘Q’ is supplied to a mono-atomic ideal gas which expands at constant pressure. The fraction of heat that goes into work done by the gas is:

• A. $\frac{2}{5}$
• B. $\frac{3}{5}$
• C. $\frac{2}{3}$
• D. 1

Answer 1

The correct option is A $\frac{2}{5}$

Quantity of heat supplied at constant pressure is given by $n{C}_{p}dT$.

Internal energy of the gas is given by $n{C}_{v}dT$.

The fraction of heat that goes into internal energy of the gas is $\frac{C_v}{C_p}$ ( and its value is $\frac{3}{5}$ for a monoatomic gas)

And the rest of energy is the work done by the gas $=1-\frac{3}{5}=\frac{2}{5}$