Two vessels A and B are of the same size and are at same temperature. A contains 1 g of hydrogen and $B$ contains 1 g of oxygen. $\mathrm{P}_{\mathrm{A}}$ and $\mathrm{P}_{\mathrm{B}}$ are the pressures of the gases in A and B respectively, then $\frac{\mathrm{P}_{\mathrm{A}}}{\mathrm{P}_{\mathrm{B}}}$ is