A solution contains a mixture of ions with the formulae shown - Edexcel - GCSE Chemistry - Question 5 - 2013 - Paper 1
Question 5
A solution contains a mixture of ions with the formulae shown.
Na⁺ Cl⁻ Mg²⁺ SO₄²⁻
Give the formulae of all the ions that will be attracted to the negatively cha... show full transcript
Worked Solution & Example Answer:A solution contains a mixture of ions with the formulae shown - Edexcel - GCSE Chemistry - Question 5 - 2013 - Paper 1
Step 1
Give the formulae of all the ions that will be attracted to the negatively charged cathode during electrolysis.
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Answer
The ions attracted to the negatively charged cathode during electrolysis are Na⁺ and Mg²⁺. Cationic species migrate towards the cathode to gain electrons.
Step 2
Explain, in terms of electrons, what is meant by reduction.
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Answer
Reduction refers to the gain of electrons by a species. When a substance undergoes reduction, it either gains electrons or loses oxygen. At the cathode, where reduction occurs, the cations gain electrons from the cathode. This process can be summarized as:
Reduction: species + electrons→reduced species
Step 3
Explain how, when solid lead bromide is melted and electrolysed, bromine is formed at the anode.
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Answer
Solid lead bromide cannot conduct electricity due to immobile ions. However, upon melting, the ionic lattice structure is broken, allowing the lead (Pb²⁺) and bromide (Br⁻) ions to move freely. During electrolysis, bromide ions migrate to the anode, where they lose electrons:
2Br−→Br2+2e−
Thus, bromine molecules (Br₂) are formed at the anode.
