Question

1 mole of NH3 gas at 27⁰C is expanded in reversible adiabatic condition to make volume 8 times ($\gamma$ = 1.33). Final temperature and work done respectively are :

• A. 150 K, 900 cal
• B. 150 K, 400 cal
• C. 250 K, 1000 cal
• D. 200 K, 800 cal

Answer 1

Answer: (A)

150 K, 900 cal

Answer 2

T1V1g–1 = T2V2g–1 $\Rightarrow$ 300 × V1/3 = T2(8V)1/3

$\Rightarrow$ T2 =150 K

W = nCv (T2 – T1) = 1 × 3 R (150 –300) = 3 × 2 (–150) = –900 cal