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

(a) 120
(b) 2400
(c) 1200
(d) 180

For a monoatomic gas like argon, $C_V$ = 3 cal/mol, $C_P$ = 5 cal/mol.
Molar heat capacity is the heat required to reaise the temperature of 1 mol 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