Question

70 cal of heat are required to raise the temperature of2 moles of an ideal diatomic gas at constant pressure from 30$^{\circ}$C to 35$^{\circ}$C. The amount of heat required (in calorie) to raise the temperature of the same gas through the same range (30$^{\circ}$C to 35$^{\circ}$C) at constant volume is

• A. 30
• B. 50
• C. 70
• D. 90

Answer 1

Answer: (B)

50

Answer 2

$Q_1 =nC_p \Delta T , Q_2 =nC_v \Delta T , \frac{Q_2}{Q_1}=\frac{C_v}{C_p} =\frac{1}{\gamma}$
$or \, \, \, \, \, \, \, \, \, \, \, \, \, \, \, Q_2 =\frac{Q_1}{\gamma} =\frac{70}{1.4}=50 cal$
$\therefore \, \, \,$ Correct option is (b)