What is the number of molecules in 2.125 g of ammonia?

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 $\text{O}_{2(g)}$.