Where will the boiling point be lower: at the seashore or on a mountain? Why?

The marsh gas detector used by miners works on the principle of

$A$ gaseous mixture was prepared by taking equal moles of $CO$ and $N_2$. If the total pressure of the mixture was found to be $1 \ atm$,the partial pressure of the nitrogen $(N_2)$ in the mixture is ............ $atm$.

$A$ sample of $O_2$ gas is collected over water at $23\,^oC$ at a barometric pressure of $751\, mm\, Hg$ (vapour pressure of water at $23\,^oC$ is $21\, mm\, Hg$). The partial pressure of $O_2$ gas in the sample collected is

The atomic masses of carbon,nitrogen,and oxygen are $12, 14$,and $16$ respectively. Which of the following pairs of gases will diffuse at the same rate?

Which gas volume is measured in a sample by using a solution of $CuCl$ in $NH_4OH$ through the measurement of volume change?