The electrochemical cell illustrated below is set up under standard conditions - NSC Physical Sciences - Question 8 - 2020 - Paper 2
Question 8
The electrochemical cell illustrated below is set up under standard conditions.
Hydrogen gas
Component X completes the circuit in the cell. State ONE other functio... show full transcript
Worked Solution & Example Answer:The electrochemical cell illustrated below is set up under standard conditions - NSC Physical Sciences - Question 8 - 2020 - Paper 2
Step 1
Component X completes the circuit in the cell. State ONE other function of component X.
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Answer
Component X provides a path for the movement of ions, ensuring electrical neutrality in the cell.
Step 2
Define the term anode.
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Answer
The anode is the electrode where oxidation takes place. It is the site of electron loss.
Step 3
Identify the anode in the cell above.
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Answer
The anode in the cell above is the magnesium (Mg) electrode.
Step 4
Write down the following: 8.4.1 Reduction half-reaction that takes place in this cell.
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The reduction half-reaction that takes place in this cell is:
ightarrow H_2(g)$$
Step 5
Write down the following: 8.4.2 NAME or FORMULA of the reducing agent in this cell.
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Answer
The reducing agent in this cell is Magnesium (Mg).
Step 6
Calculate the initial voltmeter reading of this cell under standard conditions.
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Answer
The standard cell potential for the reaction can be calculated as follows:
Ecell=Ereduction−Eoxidation
For the half-reactions, we have:
Reduction: 2H++2e−ightarrowH2 (E = 0.00 V)
Oxidation: MgightarrowMg2++2e− (E = -2.36 V)
Substituting in gives:
Ecell=0.00V−(−2.36V)=2.36V
Step 7
Fully explain why there is a change in direction of electron flow by referring to the relative strengths of the reducing agents involved.
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Answer
In the original Mg|Mg2+ half-cell, magnesium is a stronger reducing agent compared to hydrogen, resulting in magnesium losing electrons and reducing hydrogen ions. When the half-cell is replaced by Cu|Cu2+, copper is a weaker reducing agent than magnesium, which alters the balance of the reactions in the cell. In this case, the electrons will flow from the copper electrode to the ion bridge, reversing the flow since copper can no longer reduce hydrogen ions effectively.
