Q114 / 200 · NEET 2006 · Physics

The molar specific heat at constant pressure of an ideal gas is (7/2) $R$. The ratio of specific heat at constant pressure to that at constant volume is:

  • A
    $9 / 7$
  • Correct answer
    B
    $7 / 5$
  • C
    $8 / 7$
  • D
    $5 / 7$

Solution

Molar specific heat at constant pressure $$ C_P=\frac{7}{2} R $$ We know that $C_P-C_V=R$ $$ \Rightarrow \quad \begin{aligned} C_V & =C_P-R \\ & =\frac{7}{2} R-R=\frac{5}{2} R \end{aligned} $$ from (i) and (ii), $$ \therefore \quad \frac{C_P}{C_V}=\frac{7}{5} . $$

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

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