A closed 2.0 L container initially holds 3.0 ~mol^ ^ ^ of O_2(~g)...

A closed 2.0 L container initially holds $3.0 \mathrm{~mol}^{{}^{{}^{\circ}}}$ of $\mathrm{O}_2(\mathrm{~g})$ and $2.0 \mathrm{~mol} \mathrm{of}_2(\mathrm{~g})$ at room temperature, T. If the pressure remains constant when 1.0 mol of $\mathrm{O}_2(\mathrm{~g})$ is added, the final temperature of the system is-(Assume ideal gas behaviour throughout)