Question

The molar specific heat of oxygen at constant pressure $C_P=7.03cal/mo{l}^{\circ }C$ and $R=8.32J/mo{l}^{\circ }C$. The amount of heat taken by $5$ moles of oxygen when heated at constant volume from ${10}^{\circ }C$ to ${20}^{\circ }C$ will be approximately.

• A. $25cal$
• B. $50cal$
• C. $253cal$
• D. $500cal$

Answer 1

The correct option is C $253cal$

Given, $C_p=7.03cal/mo{l}^{\circ }C,$ $R=8.315J/mo{l}^{\circ }C=\frac{8.315}{4.2}cal/mo{l}^{o}C$,
$n=5moles,T_2={20}^{\circ }C,T_2={10}^{\circ }C$.
Heat taken at constant volume $△Q=n{C}_V△T$
$△Q=n(C_P-R)△T$ $[\because C_P-C_V=R]$
$△Q=5[7.03-\frac{8.31}{4.2}]\times (20-10)$ $=253cal$.