The density of air is higher at sea level. Which of the following laws explains this practical observation?

$A$ $5.75 \ g$ sample of a gas occupies $3.5 \ L$ at $55 \ ^oC$ and $0.940 \ atm$ pressure. What is the molecular weight of the gas?

Pressure of $1 \, g$ of an ideal gas $A$ at $27^{\circ} C$ is found to be $2 \, bar$. When $2 \, g$ of another ideal gas $B$ is introduced in the same flask at the same temperature,the pressure becomes $3 \, bar$. Find a relationship between their molecular masses.

At $400\, K$ temperature,the volume and pressure of a gas are $200\, mL$ and $1.5\, bar$ respectively. Calculate the volume,weight (assuming the gas is $N_2$),and the number of molecules at $STP$. $[R = 8.31 \times 10^{-2}\, L\, bar\, K^{-1}\, mol^{-1}]$.

If $20 \ cm^3$ of gas at $1 \ atm$ is expanded to $50 \ cm^3$ at constant $T$,what is the final pressure?

The value of the gas constant $R$ is $8.314 \ X$. Here,$X$ represents ......