Deep sea divers use a mixture of which gases for respiration?

Between $NH_3$ and $CO_2$,which one will diffuse faster? What will be the ratio of their rates of diffusion?

Which one of the following statements is not correct about the three states of matter,i.e.,solid,liquid,and gaseous?

In a mixture of $CO_2$ and $CH_4$ in a closed vessel at a constant temperature,the total pressure is $8.3 \times 10^4 \, Pa$. If the partial pressure of $CO_2$ is $2.8 \times 10^4 \, Pa$,what will be the partial pressure of $CH_4$?

At a constant temperature and pressure,the ratio of the densities of two gases is $1 : 16$. The ratio of their rates of diffusion will be ........

State Dalton$'$s law of partial pressures.