Question

70 calories of heat are required to raise the temperature of 2 moles of an ideal gas at constant pressure from ${30}^{\circ }Cto{35}^{\circ }C$. The amount of heat required to raise the temperature of same gas through the same range (${30}^{\circ }Cto{35}^{\circ }C$) at constant volume (R = 2 cal/mol/K)

• A. 30 cal
• B. 50 cal
• C. 70cal
• D. 90 cal

Answer 1

The correct option is B

50 cal

$dQ=n{C}_{P}dT\Rightarrow =70=2C_P.5\Rightarrow C_P=7CGSunits$

Hence $C_V=5CGSunits$

$dU=n{C}_{V}dT\Rightarrow =2\times 5\times 5\Rightarrow dU=50Cal$