Question

If $70\,cal$ of heat is required to raise the temperature of $2$ mole of an ideal gas at constant pressure from $30^{\circ}C$ to $35^{\circ}C$ , then the amount of heat required to raise the temperature of same gas through same range at constant volume is

• A. 50 cal
• B. 70 cal
• C. 60 cal
• D. 65 cal

Answer 1

Answer: (A)

50 cal

Answer 2

Form $\Delta Q=2c_p(\Delta T)$ $70=2\times C_p\times(35 - 30)$ $C_p=\frac{70}{10}=7 \,cal / mo1^oC$ $C_v =C_p-R = 7-2 = 5\, cal/mol ^{\circ}C$ $\Delta Q' = mC_v (\Delta T) = 2\times5\times5 = 50\,cal$