Question

How many calories are required to heat $40grams$ of argon from $40$ to $100^{\circ }C$ at constant volume ?($R=2cal/mol.K)$

• A. 120
• B. 2400
• C. 1200
• D. 180

Answer 1

Answer: (D)

For a monoatomic gas like argon, $C_v$ = 3 cal $mo{l}^{-1}$, Cp = 5 cal $mo{l}^{-1}$.
Molar heat capacity is the heat required to raise the temperature of 1 mole of the gas by 1${}^{\circ }$ 40 g of argon = 1 mole.
Hence, heat required to raise the temperature from 40${}^{\circ }$ to 100${}^{\circ }$C at constant volume = 3 $\times$ (100 - 40) = 180 cal