Question

Calculate the number of molecules and the number of atoms present in 11.2L of Oxygen at N.T.P.

• A. 2$N_A$ and $N_A$
• B. 0.5$N_A$ and $N_A$
• C. 0.5$N_A$ and $N_A$
• D. 0.25$N_A$ and 2$N_A$

Answer 1

The correct option is B

0.5$N_A$ and $N_A$

1 mole of any gas at N.T.P occupies 22.4L of volume at N.T.P

1 mole of $O_2$ occupies $\to$ 22.4L at N.T.P

0.5 mole of $O_2$ occupies $\to$ 11.2L at N.T.P

1 mole of $O_2$ have Avogadro number molecules [$N_A$].

0.5 mole of $O_2$ have 0.5$N_A$ = 0.5 $\times 6.022\times {10}^{23}$ = 3$\times {10}^{23}$

1 mole of $O_2$ have 2 atoms of Oxygen.

0.5 $\times 6.022\times {10}^{23}$ molecules have $2\times 0.5\times 6.022\times {10}^{23}$ atoms of Oxygen.