For an ideal gas,the $V$ vs $T$ plot at constant pressures $P_1$ and $P_2$ is shown in the figure. Which of the following is correct?

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.

$100 \, g$ of an ideal gas is kept in a cylinder of $416 \, L$ volume at $27^{\circ} C$ under $1.5 \, bar$ pressure. The molar mass of the gas is $.... \, g \, mol^{-1}$. (Nearest integer) (Given : $R = 0.083 \, L \, bar \, K^{-1} \, mol^{-1}$)

For a fixed amount of gas at a constant temperature,which of the following is true?

The density of $O_{2(g)}$ is maximum at?

The density of a gas is equal to ...... ($P =$ pressure,$V =$ volume,$T =$ temperature,$R =$ gas constant,$n =$ number of moles,and $M_w =$ molecular weight):