At constant temperature and pressure,what is the volume of $n$ moles of different gases?

At a temperature of $300 \ K$,if the pressure of $0.09 \ mol$ of a gas is halved,what will be its volume?

Air entering the lungs ends up in tiny sacs called alveoli. It is from the alveoli that oxygen diffuses into the blood. The average radius of the alveoli is $0.0050 \ cm$ and the air inside contains $14$ per cent oxygen. Assuming that the pressure in the alveoli is $1.0 \ atm$ and the temperature is $37 \ ^oC$,calculate the number of oxygen molecules in one of the alveoli.

For a fixed mass of an ideal gas,the following graph is given. Determine the correct relationship between $P_1, P_2$ and $P_3$.

Which graph is not a straight line for an ideal gas?

$A$ gas is present at a pressure of $2 \,atm$. What should be the increase in pressure, so that the volume of the gas can be decreased to $\frac{1}{4}$ of the initial volume at constant temperature (in $\,atm$)?