Question

Calculate the number of particles in:
15.9 g of ferrous sulphate
20.34 moles of oxygen gas
45.66 g of water
100.1 g of ammonia
45.82 g of potassium permanganate.​

Answer 1

we have to calculate the number of particles in,

1. 15.9 g of ferrous sulphate
2. 20.34 moles of oxygen gas
3. 45.66 g of water
4. 100.1 g of ammonia
5. 45.82g of potassium permanganate

solution : 1. molecular mass of ferrous sulphate = 151.9 g/mol

given mass = 15.9 g

so no moles of ferrous sulphate = 15.9/151.9 = 0.105

now no of particles (molecules) = no of moles × Avogadro's number

= 0.105 × 6.023 × 10²³

= 0.6324 × 10²³

2. no of oxygen molecules = no of moles × Avogadro's number

= 20.34 × 6.023 × 10²³

= 122.5 × 10²³

= 1.225 × 10²⁵

3. molecular mass of water = 18g/mol

given mass = 45.66g

so no of moles of water = 45.66/18 = 2.54

now no of particles (molecules) = 2.54 × 6.023 × 10²³ = 1.53 × 10²⁴

4. given mass of ammonia = 100.1 g

molecular mass of ammonia = 17g/mol

so no of moles of ammonia = 100.1/17 = 5.88

now no of particles = 5.88 × 6.023 × 10²³

= 3.54 × 10²⁴

5. given mass of potassium permanganate = 45.82g

molecular mass of potassium permanganate = 158 g/mol

so no of moles of potassium permanganate = 45.82/158 = 0.3

now no of particles = 0.3 × 6.023 × 10²³

= 1.8069 × 10²³