1) Two moles of ideal helium gas are in a rubber balloon at $30^{0}C$. 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 $35^{0}C$. The amount of heat required in raising the temperature is nearly (take R=8.31 J/mol-K) A) 62 J B) 104J C) 124 J D) 208J Answer: Option DExplanation:The process may be assumed to be isobaric. $\therefore$ $Q=nC_{P} \triangle T=(2)\left(\frac{5}{2}R\right)(5)$ =$5 \times 8.31 \times 5$ =207.75 J=208J
