The cell notation Zn(s)|Zn^{2+}(aq)|Cu^{2+}(aq)|Cu(s) represents a galvanic cell operating under standard conditions - NSC Technical Sciences - Question 6 - 2020 - Paper 2
Question 6
The cell notation Zn(s)|Zn^{2+}(aq)|Cu^{2+}(aq)|Cu(s) represents a galvanic cell operating under standard conditions.
6.1.1 Define the term galvanic cell.
6.1.2 Dr... show full transcript
Worked Solution & Example Answer:The cell notation Zn(s)|Zn^{2+}(aq)|Cu^{2+}(aq)|Cu(s) represents a galvanic cell operating under standard conditions - NSC Technical Sciences - Question 6 - 2020 - Paper 2
Step 1
Define the term galvanic cell.
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Answer
A galvanic cell is an electrochemical cell that converts chemical energy into electrical energy. This process occurs through spontaneous redox reactions, where oxidation and reduction take place at separate electrodes.
Step 2
Draw a labelled diagram to represent the Zn-Cu cell. Show the direction of electron flow in the external circuit.
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Answer
The diagram of the Zn-Cu galvanic cell includes:
Anode: Zn electrode in ZnSO₄ solution
Cathode: Cu electrode in CuSO₄ solution
Salt bridge: connects the two half-cells
Voltmeter: measures the voltage developed by the cell
The direction of electron flow is from the anode (Zn) to the cathode (Cu).
Step 3
Write down TWO standard conditions under which the Zn-Cu cell operates.
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The temperature should be 25°C.
The concentration of the electrolytes should be 1 mol/dm³.
Step 4
To which half-cell do the anions in the salt bridge migrate?
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The anions in the salt bridge migrate towards the anode half-cell.
Step 5
Explain the answer to QUESTION 6.1.4.
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Answer
Anions migrate towards the anode to maintain electrical neutrality in the cell. As oxidation occurs at the anode, positive charge builds up there, which needs to be balanced by the flow of anions from the salt bridge.
Step 6
Identify electrode X by means of a calculation.
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Answer
Given that the cell potential (E) is 2.00 V and that Cu²⁺/Cu is the cathode, we can use the Nernst equation to identify Electrode X. Assuming electrode X is aluminum (Al), and calculating its standard reduction potential gives:
E°{cell} = E°{cathode} - E°{anode}
2.00 V = E°{Cu²⁺/Cu} - E°_{Al³⁺/Al}
Thus, Electrode X is aluminum.
Step 7
Write down the half-reaction taking place at the anode.
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Answer
At the anode where zinc oxidation occurs:
Zn(s) → Zn²⁺(aq) + 2e⁻.
Step 8
Which electrode will experience a decrease in mass?
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The anode, where zinc is oxidized, will experience a decrease in mass as Zn atoms are converted to Zn²⁺ ions.
Step 9
Explain the answer to QUESTION 6.2.3.
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The anode will decrease in mass because the zinc solid is oxidized to zinc ions, which enter the solution. This oxidation results in the loss of material from the anode, causing its mass to decrease.
