# GATE2020: 32

A tank initially contains a gas mixture with $21\:mol\:\%$ oxygen and $79\:mol\:\%$ nitrogen. Pure nitrogen enters the tank, and a gas mixture of nitrogen and oxygen exits the tank. The molar flow rate of both the inlet and exit streams is $8\: mol\: s^{-1}$.

In addition, use the following data and assumptions

• Assume the tank contents to be well mixed
• Assume ideal gas behavior
• The temperature and pressure inside the tank are held constant
• Molar density of the gas mixture in the tank is constant at $40\:mol\:m^{-3}$

If the volume of the tank is $20\: m^3$, then the time (in seconds) required for oxygen content in the tank to decrease to $1\:mol\:\%$ is

1. $100.45$
2. $304.45$
3. $3.445$
4. $10$
in Others
edited