Q. Two moles of ideal helium gas are in a rubber balloon at $30℃$. The balloon is fully expandable and can be assumed to require no energy in its expansion. The temperature of the gas in the balloon is slowly changed to $35℃$. The amount of heat required in raising the temperature is nearly (take $R = 8.31\ J/mol.K)$
A) $62J$
B) $104J$
C) $124J$
D) $208J$
Explanation
(d) $\mathrm{\Delta}Q = nC_{P}\mathrm{\Delta}T$
$= 2\left( \frac{3}{2}R + R \right)\mathrm{\Delta}T$
$= 2\left\lbrack \frac{3}{2}R + R \right\rbrack \times 5$
$= 2 \times \frac{5}{2} \times 8.31 \times 5$
$= 208\ J$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.