Question

If R is universal gas constant, the amount of heat needed to raise the temperature of 2 moles of an ideal monatomic gas from 273 K to 373 K when no work is done is:

• A. 100R
• B. 150R
• C. 300R
• D. 500R

Answer 1

Answer: (C)

300R

If a gas is heated at constant volume then no work is done. The heat supplies is given by,

$dQ=n{C}_{V}dT$

But $C_V=\frac{f}{2}R$

where $f$ is the degree of freedom of the gas.

For a monoatomic gas, the degree of freedom of the gas is $3$.

$\therefore dQ=\frac{nfRdT}{2}$

$=\frac{2\times 3\times R\times (373-273)}{2}=300R$