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 g of sodium hydroxide.
[H = 1, O = 16, Na = 23, S = 32, Cu = 64]
(ii) What is the colour of the precipitate formed.
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(i)
$$\begin{matrix} 2\text{NaOH} & + & \text{CuSO}_4 & \longrightarrow & \text{Na}_2\text{SO}_4 & + & \text{Cu(OH)}_2\downarrow \\ 2[23 + 16 & & & & & & 64 + 2[40] \\ + 1] & & & & & & = 98 \text{g} \\ = 80 \text{ g} & & & & & & \\ \end{matrix}$$
80 g of sodium hydroxide precipitates 98 g of copper hydroxide.
∴ 200 g of sodium hydroxide will precipitate $\frac{98}{80}$ x 200 = 245 g of copper hydroxide.
Hence, 245 g. of copper hydroxide is precipitated.
(ii) Pale blue precipitate is formed.