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ICSE Class 10 Chemistry Question 20 of 28

Stoichiometry — Percentage Composition — Empirical & Molecular Formula — Chemical Equations — Question 28

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Question

Question 1(2019)

Copper [II] sulphate soln. reacts with sodium hydroxide soln. to form copper hydroxide according to the equation :

2NaOH + CuSO4 ⟶ Na2SO4 + Cu(OH)2↓

What mass of copper hydroxide is precipitated by using 200 g of sodium hydroxide.

[H = 1, O = 16, Na = 23, S = 32, Cu = 64]

Answer

2NaOH+CuSO4⟶Na2SO4+Cu(OH)2↓2[23+1664+2[40]+1]=98g=80 g\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 9880\dfrac{98}{80} x 200 = 245 g of copper hydroxide.

Hence, 245 g. of copper hydroxide is precipitated.