(a) (i) In solution copper chloride, CuCl₂, reacts with potassium hydroxide, KOH, to form copper hydroxide, Cu(OH)₂, and potassium chloride - Edexcel - GCSE Chemistry - Question 4 - 2017 - Paper 1

The state symbol for a precipitate is (s), indicating that copper hydroxide is in solid form.

To calculate the relative formula mass of copper hydroxide, Cu(OH)₂:

$\text{Ram of Cu} + 2 \times \text{Ram of O} + 2 \times \text{Ram of H} = 63.5 + 2 \times 16 + 2 \times 1 = 63.5 + 32 + 2 = 97.5$

From the given options, the correct relative formula mass is C, 97.5.

First, calculate the number of moles of copper (Cu) and sulfur (S):

Moles of Cu:

$\text{Moles of Cu} = \frac{12.7 \, \text{g}}{63.5 \, \text{g/mol}} \approx 0.200 \text{ mol}$

Moles of S:

$\text{Moles of S} = \frac{3.2 \, \text{g}}{32 \, \text{g/mol}} \approx 0.100 \text{ mol}$

Next, simplify the ratio:

$\text{Ratio of Cu:S} = \frac{0.200}{0.100} = 2:1$

Thus, the empirical formula of copper sulfide is Cu₂S.

To find the maximum mass of copper oxide (CuO), first calculate the number of moles of copper:

$\text{Moles of Cu} = \frac{25.4 \, \text{g}}{63.5 \, \text{g/mol}} \approx 0.400 \text{ mol}$

Since the reaction is:

$2\text{Cu} + \text{O}_2 \rightarrow 2\text{CuO}$

The moles of CuO produced are equal to the moles of Cu:

Thus, moles of CuO produced = 0.400 mol.

Calculate the mass of CuO:

$\text{Mass of CuO} = \text{Moles} \times \text{Molar Mass} = 0.400 \, \text{mol} \times 79.5 \, \text{g/mol} = 31.8 \, \text{g}$

Therefore, the maximum mass of copper oxide formed is 31.8 g.