Identify pair of orbitals having similar $(n + l)$ values from the following.

What is the proportionality between (I) Bond length and size of atom (II) Bond length and multiplicity of bond respectively?

A mixture of 0.5 mol $\text{N}_2$ gas, 1.0 mol $\text{O}_2$ gas and 1.5 mol $\text{H}_2$ gas exerts a total pressure of 18 bar. Find the partial pressure of $\text{O}_{2(g)}$.

The enthalpy of combustion of C, $\text{H}_2$, and $\text{CH}_4$ are $-390$, $-285$ and $-890$ kJ/mol. Find the enthalpy of formation of methane.