Learners want to identify an unknown metal X using a standard half-cell, X | X²⁺. They set up an electrochemical cell under standard conditions using two half-cells, as shown in the diagram below. The initial emf of this cell is 1,20 V. 8.1 State the standard conditions under which this cell functions. 8.2 State ONE function of component Y. After the cell has operated for some time, it is found that the mass of electrode X has increased. 8.3 Identify X by means of a suitable calculation. 8.4 Write down the oxidation half-reaction that takes place in this cell. Half-cell X | X²⁺ is now replaced by an Au | Au³⁺ half-cell. The initial emf of the cell is now 1,50 V. As the cell operates, the Au electrode increases in mass. 8.5 Arrange the oxidising agents: X²⁺, Au³⁺ and H⁺, in order of increasing strength. Fully explain the answer.

NSC Physical Sciences Electrochemistry: Learners want to identify an unk

Learners want to identify an unknown metal X using a standard half-cell, X | X²⁺ - NSC Physical Sciences - Question 8 - 2023 - Paper 2

Question 8

Learners want to identify an unknown metal X using a standard half-cell, X | X²⁺. They set up an electrochemical cell under standard conditions using two half-cells,... show full transcript

Worked Solution & Example Answer:Learners want to identify an unknown metal X using a standard half-cell, X | X²⁺ - NSC Physical Sciences - Question 8 - 2023 - Paper 2

Step 1

8.1 State the standard conditions under which this cell functions.

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Answer

The standard conditions for the electrochemical cell to function include:

A temperature of 25°C (298 K).
A pressure of 1 atm for gaseous reactants and products.
Concentrations of 1 M for all aqueous solutions.

Step 2

8.2 State ONE function of component Y.

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Answer

Component Y acts as a salt bridge, which allows for the flow of ions between the two half-cells, maintaining electrical neutrality and preventing the solutions from mixing.

Step 3

8.3 Identify X by means of a suitable calculation.

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Answer

Given the initial emf of 1.20 V, we use the Nernst equation to identify X:

$E = E^0 - \frac{RT}{nF} \ln Q$

Since we know the standard potential for H⁺/H₂ is 0.00 V, and for the unknown metal half cell needs to be calculated:

Emf of the cell: 1.20 V = E^0(X) - 0.00 V.
Therefore, E^0(X) = 1.20 V.
By consulting the standard reduction potentials table, we can conclude that X is likely to be Pt (platinum) since it has a higher reduction potential compared to hydrogen.

Step 4

8.4 Write down the oxidation half-reaction that takes place in this cell.

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Answer

The oxidation half-reaction occurring at electrode X can be represented as:

$X^2+ + 2e^- \rightarrow X(s)$

Step 5

8.5 Arrange the oxidising agents: X²⁺, Au³⁺ and H⁺, in order of increasing strength.

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Answer

In order of increasing strength, the oxidising agents can be arranged as follows:

H⁺
X²⁺
Au³⁺

This is based on their standard reduction potentials, where Au³⁺ has the highest potential, making it the strongest oxidising agent.

Learners want to identify an unknown metal X using a standard half-cell, X | X²⁺ - NSC Physical Sciences - Question 8 - 2023 - Paper 2

Worked Solution & Example Answer:Learners want to identify an unknown metal X using a standard half-cell, X | X²⁺ - NSC Physical Sciences - Question 8 - 2023 - Paper 2

8.1 State the standard conditions under which this cell functions.

8.2 State ONE function of component Y.

8.3 Identify X by means of a suitable calculation.

8.4 Write down the oxidation half-reaction that takes place in this cell.

8.5 Arrange the oxidising agents: X²⁺, Au³⁺ and H⁺, in order of increasing strength.

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