Question

When $229J$ of energy is supplied as heat as 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. $40J$ $K^{-1}$ $mo{l}^{-1}$
• B. $30J$ $K^{-1}$ $mo{l}^{-1}$
• C. $21.7J$ $K^{-1}$ $mo{l}^{-1}$
• D. $81.7J$ $K^{-1}$ $mo{l}^{-1}$

Answer 1

The correct option is C $21.7J$ $K^{-1}$ $mo{l}^{-1}$

$\begin{array}{c}Q=n{C}_v\Delta T\\ n=3mole\\ \Delta T=2.55K\\ 229=3\times C_P\times 2.55\\ C_P=29.334\\ 29.334-C_v=8.314\\ C_v\approx 21.7J{K}^{-1}mo{l}^{-1}\end{array}$
Option C is correct.