Question

For a monatomic gas, the molar specific heat at constant pressure divided by the molar gas constant $R$ is equal to

• A. 2.5
• B. 1.5
• C. 5
• D. 3.5

Answer 1

Answer: (A)

2.5

Answer 2

For a monoatomic gas,
$\frac{C_{p}}{C_{V}}=\gamma =1.67$
or $C_{p}-1.67 C_{V} =0$ ...(i)
$C_{p}-C_{V} =R$ ...(ii)
On multiplying E (ii) by $1.67$ and subtracting E (i) from it, we get
$0.67\, C_{p} =1.67 R$
$\frac{C_{p}}{R} =\frac{1.67}{0.67}$
$\frac{C_{p}}{R} =2.492 \approx 2.5$