Ncert Exercises & Solutions

Which of the following pairs have the same number of atoms?

1. 16 g of O₂(g) and 4 g of H₂(g)

2. 16 g of O₂ and 44 g of CO₂

3. 28 g of N₂ and 32 g of O₂

4. 12 g of C(s) and 23 g of Na(s)

(c, d)

(c)

Number of atoms in 28 g of N_{2} = \frac{28}{28} \times N_{A} \times 2 = 2 N_{A} (where, N = Avogadro number)

Number of atoms in 32 g of O_{2} = \frac{32}{32} \times N_{A} \times 2 = 2 N_{A}

(d)

12 g of C (s) contains atoms = \frac{12}{12} \times N_{A} \times 1 = N

Number of atoms in 23 g of Na (s) = \frac{23}{23} \times N \times 1 = N_{A}