If $P$ is pressure and $\rho$ is density of a gas,then $P$ and $\rho$ are related as

Under what conditions does a gas behave ideally? Why?

$A$ 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 $\,atm$)?

The density of nitrogen monoxide $(NO)$ at $S.T.P.$ is ......... $g \ L^{-1}$.

At very low pressure,the compressibility factor $Z$ of a $CO_2$ gas with constant molar volume is:

$A$ balloon filled with an air sample occupies $3 \,L$ volume at $35^{\circ} C$. On lowering the temperature to $T$, the volume decreases to $2.5 \,L$. The temperature $T$ is (in $^{\circ} C$)? [Assume $p$-constant]