Answer
(a) equal to
(b) less than
Work Step by Step
(a) The number of molecules in one mole of any substance is known as Avogadro's number, which is a constant number that is $6.023 \times 10^{23}$. Thus, one mole of both $N_2$ and $O_2$ has an equal number of molecules.
(b) We know that molecular mass of every substance is different. The molecular mass of $N_2=14$ is less than that of $O_2=16$.