Question

A rigid tank contains 6 kg of an ideal gas at 3
atm and 40°C. Now a valve is opened, and
half of mass of the gas is allowed to escape. If
the final pressure in the tank is 2.2 atm, the final
temperature in the tank is
(a) 186°C
(b) 59°C
(C) - 43°C
(d) 20°C​

Answer 1

Initial mass - 6kg

Initial Temp. -  40°C

Initial pressure - 3atm

Final mass - 3kg

Final Temp. - ?

Final pressure - 2.2atm

$\frac{6}{40}$ $=\frac{3}{x}$

cross multiply

6x = 120

divide both sides by 6

$\frac{6x}{6} = \frac{120}{6}$

x = 20°C

Answer is (d)