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a) A solution contains a mixture of ions with the formulae shown - Edexcel - GCSE Chemistry - Question 5 - 2013 - Paper 1
Question 5
a) A solution contains a mixture of ions with the formulae shown. Na^+, Cl^-, Mg^{2+}, SO_4^{2-} Give the formulae of all the ions that will be attracted to the neg... show full transcript
Worked Solution & Example Answer:a) A solution contains a mixture of ions with the formulae shown - Edexcel - GCSE Chemistry - Question 5 - 2013 - Paper 1
Step 1
a) Give the formulae of all the ions that will be attracted to the negatively charged cathode during electrolysis.
Answer
The ions that will be attracted to the negatively charged cathode are Na^+ and Mg^{2+}. Cations, which are positively charged, are attracted to the cathode where reduction occurs.
Step 2
b) Explain, in terms of electrons, what is meant by reduction.
Answer
Reduction refers to the gain of electrons. When a species is reduced, it receives electrons from the cathode. This results in a decrease in oxidation state. For example, if a cation gains electrons, it is reduced to a neutral atom.
Step 3
c) Explain how, when solid lead bromide is melted and electrolysed, bromine is formed at the anode.
Answer
Solid lead bromide (PbBr_2) consists of ions that cannot move due to its rigid lattice structure. When melted, the ions can move freely. During electrolysis, bromide ions (Br^-) are attracted to the anode, where they lose electrons. This process oxidizes the bromide ions, forming bromine molecules (Br_2) at the anode.