Calculate the number of atoms in 10 litres of ammonia [N = 14, H = 1]

1 mole of NH₃ = N + 3 H = 4 atoms = 4 x 6.023 x 10²³ atoms and occupies 22.4 lit at s.t.p.

If 22.4 lit of NH₃ has 4 x 6.023 x 10²³ atoms,

then, 10 lit will have

$= \dfrac{4 \times 6.023 \times 10^{23}}{22.4} \times 10 \\[0.5em] = \dfrac{40}{22.4} \times 6.023 \times 10^{23} \\[0.5em] = 1.786 \times 6.023 \times 10^{23} \text{ atoms}$

Hence, number of atoms in 10 litres of ammonia = 1.786 x 6.023 x 10²³ atoms