11. Answer any two of the parts (a), (b) and (c) - Leaving Cert Chemistry - Question 11 - 2010
Question 11
11. Answer any two of the parts (a), (b) and (c).
(a) The apparatus shown on the right was used to investigate the electrolysis of aqueous sodium sulfate to which a... show full transcript
Worked Solution & Example Answer:11. Answer any two of the parts (a), (b) and (c) - Leaving Cert Chemistry - Question 11 - 2010
Step 1
Name a material suitable for use as the electrodes A and B.
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Answer
A suitable material for the electrodes A and B would be platinum, as it is chemically inert and conductive. Alternatives like carbon or graphite could also be acceptable.
Step 2
How was the current conducted through the electrolyte?
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Answer
The current was conducted through the electrolyte by the movement of ions. When the electric field is applied, cations move towards the negative electrode and anions move towards the positive electrode.
Step 3
At which electrode, A or B, did oxidation occur?
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Oxidation occurred at electrode B.
Step 4
Write the equation for the reaction that occurred at this electrode.
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Answer
The reaction at electrode B can be represented as:
ightarrow 2H^+ + rac{1}{2}O_2 + 2e^-$$
This reaction involves the decomposition of water into hydrogen ions, oxygen gas, and electrons.
Step 5
When a current passed through the electrolyte for 15 minutes, 8.5 cm³ of gas was collected above the positive electrode. What volume of gas was collected above the negative electrode in the same time?
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Answer
Since electrolysis generally produces gases at both electrodes, the volume of gas collected above the negative electrode is equal to that above the positive electrode. Therefore, 8.5 cm³ of gas would also have been collected above the negative electrode.
Step 6
At which electrode did a blue colour appear? Justify your answer.
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The blue color appeared at electrode A. This occurs because hydroxide ions (OH⁻) are generated at the negative electrode, potentially reacting with the universal indicator to produce a blue color in the solution.
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