Question

When $229J$ of energy is supplied as heat at constant pressure to $3$ mol $Ar\left(g\right)$, the temperature of the sample is increased by $2.55K$. Calculate the molar heat capacity at constant volume:

• A. $30KJ{K}^{-1}{mol}^{-1}$
• B. $30J{K}^{-1}{mol}^{-1}$
• C. $21.7J{K}^{-1}{mol}^{-1}$
• D. $21.7KJ{K}^{-1}{mol}^{-1}$

Answer 1

Answer: (C)

$21.7J{K}^{-1}{mol}^{-1}$

$Cp-Cv=nR$

$Cp=q/\Delta T$

$Cp=229J/2.55K$ $=89.80J{k}^{-1}$

$Cv=Cp-nR=89.80-(3\times 8.314)=64.86J{k}^{-1}$

$Cv$ per mol $=64.86/3=21.6J{k}^{-1}mo{l}^{-1}$

$21.6J{k}^{-1}mol{l}^{-1}$