Question

The molar specific heat of oxygen at constant pressure $C_{p}=7.03\, cal / mol { }^{\circ} C$ and $R =8.31\, J / mol { }^{\circ} C$. 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. 25 cal
• B. 50 cal
• C. 253 cal
• D. 500 cal

Answer 1

Answer: (C)

Given, $C_{p}=7.03\, cal / mol ^{\circ} C , R =8.315 / mol ^{\circ} C$,
$n =5$ moles, $T_{2}=20^{\circ} C , T_{1}=10^{\circ} C$,
$\Delta Q =?$
$\therefore $ Heat, $\Delta Q =n C_{V} \Delta T=n\left(C_{p}-R\right) \Delta T$
$=5\left[7.03-\frac{831}{4.2}\right] \times(20-10) \simeq 253\, cal$