Question

Copper sulphate solution reacts with sodium hydroxide solution to form a precipitate of copper hydroxide according to the equation : 
2NaOH + CuSO₄ → Na₂SO₄ + Cu (OH)₂ ↓
(i) What mass of copper hydroxide is precipitated by using 200 gm of sodium hydroxide? 
[H = 1, O = 16, Na = 23, S = 32, Cu = 64]

(ii) What is the colour of the precipitate formed?

Answer 1

The Given equation is 

2NaOH + CuSO₄ → Na₂SO₄ + Cu(OH)₂ ↓

(i) Molecular weight of NaOH , Sodium hydroxide = 23 + 16 + 1 = 40

Molecular weight of Cu(OH)₂ ,

Copper hydroxide = 64 + 16 + 1 + 16 + 1 = 98

Now , 40g of NaOH is used to precipitate 98g of Cu(OH)₂

Hence , 200g of NaOH will be used to precipitate (98/40)200 g of Cu(OH)₂ = 490g of Cu(OH)₂ .

So , 490g of copper hydroxide would be prepared using 200g of sodium hydroxide .

(ii) A light blue precipitate of Cu(OH)₂ will be formed .