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At the start of the day, a student set up a galvanic cell using two electrodes: nickel, Ni, and metal X - VCE - SSCE Chemistry - Question 5 - 2019 - Paper 1
Question 5
At the start of the day, a student set up a galvanic cell using two electrodes: nickel, Ni, and metal X. This set-up is shown in the diagram below. Consider the fol... show full transcript
Worked Solution & Example Answer:At the start of the day, a student set up a galvanic cell using two electrodes: nickel, Ni, and metal X - VCE - SSCE Chemistry - Question 5 - 2019 - Paper 1
Step 1
Consider the alternative metals
Answer
To determine which metals can replace metal X and produce a darker green solution in Half-cell 1, we need to consider their reduction potentials.
The metals listed are: zinc (Zn), lead (Pb), cadmium (Cd), and copper (Cu). In a galvanic cell, a reduction potential that is higher than that of nickel (Ni) will enhance the reaction and give a darker coloration to the solution.
Typical reactions involve the mixing of solutions and the displacement of ions, where the solution changes colour based on the metal's ability to react with the Ni²⁺ ions in the half-cell.
Step 2
Identify viable substitutes
Answer
Upon analysis, the following points can be made:
- Zinc (Zn): Has a lower reduction potential than Ni, hence cannot replace.
- Lead (Pb): Also has a lower reduction potential than Ni.
- Cadmium (Cd): While it has a reduction potential similar to Ni, it would not contribute significantly to darkening the solution.
- Copper (Cu): Has a higher reduction potential than Ni, allowing it to participate effectively in the electron transfer, thus darkening the solution.
Thus, metals that could cause the solution to become darker green are related to their oxidation and reduction behaviour.
Step 3
Select correct answer choice
Answer
Considering the reactions and potentials, the viable substitutions that could lead to a darker green solution in Half-cell 1 include metals 2 and 4 (lead and copper). However, copper's effective contribution to the cell reaction makes it a preferred choice.
Therefore, the correct answer is: B. metals 2 and 4.