Q136 / 160 · AP EAMCET 2015 · Physics

The specific heat of helium at constant volume is 12.6 $\mathrm{Jmol}^{-1} \mathrm{~K}^{-1}$. The specific heat of helium at constant pressure in $\mathrm{Jmol}^{-1} \mathrm{~K}^{-1}$ is about (Assume the temperature of the gas is moderate, universal gas constant, $R=8.314 \mathrm{Jmol}^{-1} \mathrm{~K}^{-1}$ )

  • A
    $12.6$
  • B
    $16.8$
  • C
    $18.9$
  • Correct answer
    D
    $21$

Solution

As $C_V=12.6 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}$ is given in SI unit So, $R=8314 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}$ Then, $C_p=C_V+R=12.6+8.314=21$

Hence, the correct answer is option: 'D'.

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