Copper hydroxide, copper oxide and copper sulfide are three compounds of copper - Edexcel - GCSE Chemistry - Question 4 - 2017 - Paper 1
Question 4
Copper hydroxide, copper oxide and copper sulfide are three compounds of copper.
(a) (i) In solution copper chloride, CuCl₂, reacts with potassium hydroxide, KOH, ... show full transcript
Worked Solution & Example Answer:Copper hydroxide, copper oxide and copper sulfide are three compounds of copper - Edexcel - GCSE Chemistry - Question 4 - 2017 - Paper 1
Step 1
Write the balanced equation for this reaction.
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Answer
The balanced equation for the reaction between copper chloride and potassium hydroxide is:
CuCl2+2KOH→Cu(OH)2+2KCl
In this equation, the left-hand side (LHS) and right-hand side (RHS) are balanced with respect to the number of each type of atom.
Step 2
Which state symbol would be used in the equation to show that copper hydroxide is a precipitate?
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Answer
The state symbol to indicate a precipitate is (s) for solid. Thus, you would put a cross (✗) next to option C.
Step 3
Which of the following is the relative formula mass for copper hydroxide?
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Answer
To calculate the relative formula mass of Cu(OH)₂, we sum the atomic masses:
Relative mass=63.5+2(16)+1=97.5g/mol
Thus, you would put a cross (✗) next to option C.
Step 4
Calculate the empirical formula of the copper sulfide.
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Answer
First, we need to determine the moles of copper and sulfur:
Moles of copper:
Moles of Cu=63.5g/mol12.7g=0.2mol
Moles of sulfur:
Moles of S=32g/mol3.2g=0.1mol
The ratio of moles of Cu to S is:
Ratio=0.10.2=2:1
Thus, the empirical formula of copper sulfide is Cu₂S.
Step 5
Calculate the maximum mass of copper oxide.
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Answer
To find the maximum mass of copper oxide (CuO) formed:
Find moles of copper used:
Moles of Cu=63.5g/mol25.4g≈0.4mol
From the equation 2Cu + O₂ → 2CuO, 2 moles of Cu produce 2 moles of CuO. Therefore:
Moles of CuO=0.4mol
Calculate the mass of CuO:
Mass of CuO=0.4mol×79.5g/mol=31.8g
Thus, the maximum mass of copper oxide that can be formed is approximately 31.8 g.
