Define oxidation in terms of electron transfer. The electrolysis, using inert electrodes, of aqueous potassium iodide, KI, to which a few drops of phenolphthalein indicator have been added, is shown in the diagram. (i) Name a suitable material for the electrodes. (ii) Write balanced half equations for the reactions that take place at the electrodes. (iii) Explain the colour change observed at the positive electrode (anode).

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Define oxidation in terms of electron transfer - Leaving Cert Chemistry - Question b - 2009

Question b

Define oxidation in terms of electron transfer. The electrolysis, using inert electrodes, of aqueous potassium iodide, KI, to which a few drops of phenolphthalein i... show full transcript

Worked Solution & Example Answer:Define oxidation in terms of electron transfer - Leaving Cert Chemistry - Question b - 2009

Step 1

Define oxidation in terms of electron transfer

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Answer

Oxidation is defined as the process of loss of electrons from a substance. During this process, the oxidation state of the substance increases.

Step 2

Name a suitable material for the electrodes

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Answer

A suitable material for the electrodes is platinum or carbon (graphite).

Step 3

Write balanced half equations for the reactions that take place at the electrodes

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Answer

For the anode reaction:

$2I^- \rightarrow I_2 + 2e^-$

For the cathode reaction:

$2H_2O + 2e^- \rightarrow H_2 + 2OH^-$

Step 4

Explain the colour change observed at the positive electrode (anode)

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Answer

At the positive electrode (anode), iodine is produced. The phenolphthalein indicator changes colour due to the presence of iodine, which can be observed as a red, orange, yellow, brown, or a combination of these colours. This is because iodine has a distinct colour that indicates its formation during the electrolysis process.

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Define oxidation in terms of electron transfer - Leaving Cert Chemistry - Question b - 2009

Worked Solution & Example Answer:Define oxidation in terms of electron transfer - Leaving Cert Chemistry - Question b - 2009

Define oxidation in terms of electron transfer

Name a suitable material for the electrodes

Write balanced half equations for the reactions that take place at the electrodes

Explain the colour change observed at the positive electrode (anode)

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