Question

Calculate number of atoms in each of following (1) 0.4 mole nitrogen (2) 1.6 gram of salter

Answer 1

1. Approximately $4.82 \times 10^{23}$ atoms of nitrogen.

2. Approximately $3.29 \times 10^{22}$ atoms in 1.6 g of salt (NaCl).

Answer 2

Solution:

1. 0.4 mole Nitrogen:
   Since nitrogen in its standard state is diatomic (N₂), 0.4 mole of N₂ molecules contains

$$\text{Number of } N_2 \text{ molecules} = 0.4 \times N_A,$$

where $N_A = 6.02 \times 10^{23}$.
Each molecule has 2 atoms so,

$$\text{Total atoms} = 0.4 \times 2 \times 6.02 \times 10^{23} \approx 4.82 \times 10^{23}\, \text{atoms}.$$

2. 1.6 gram of Salter (Assumed NaCl):
   For sodium chloride, the molar mass is approximately

$$M(\text{NaCl}) = 23 + 35.5 = 58.5 \, \text{g/mol}.$$

Number of moles in 1.6 grams:

$$n = \frac{1.6}{58.5} \approx 0.02735 \, \text{moles}.$$

Each formula unit of NaCl contains 2 atoms (Na and Cl), so the total number of atoms is:

$$\text{Total atoms} = 0.02735 \times 6.02 \times 10^{23} \times 2 \approx 3.29 \times 10^{22}\, \text{atoms}.$$