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Electrochemical reactions are involved in the corrosion of metals, corrosion prevention and in the extraction of metals from their salts - Leaving Cert Chemistry - Question B - 2022
Question B
Electrochemical reactions are involved in the corrosion of metals, corrosion prevention and in the extraction of metals from their salts. Galvanising is a method of... show full transcript
Worked Solution & Example Answer:Electrochemical reactions are involved in the corrosion of metals, corrosion prevention and in the extraction of metals from their salts - Leaving Cert Chemistry - Question B - 2022
Step 1
Explain how galvanising protects an iron object from corrosion even when the zinc coat is scratched.
Answer
Galvanising protects iron objects through the principles of electrochemistry. Zinc, being higher up the electrochemical series than iron, is more easily oxidized. When the zinc coating is scratched and exposes the iron beneath, the zinc will corrode first before the iron does, thus providing sacrificial protection. As long as any zinc remains, it will protect the iron from oxidation, preventing rust formation.
Step 2
Step 3
How does a sacrificial anode help protect the steel hull of a ship from rusting?
Answer
A sacrificial anode is more electropositive than the steel it protects. When attached to the hull, it will corrode in place of the steel. This occurs because the sacrificial anode donates electrons to the steel, thereby reducing its oxidation potential. As a result, the steel hull of the ship remains protected from rusting.
Step 4
What is anodised aluminium?
Answer
Anodised aluminium is aluminum that has been treated electrochemically to form a thick layer of aluminum oxide (Al₂O₃) on its surface. This oxide layer enhances corrosion resistance and improves surface durability without the need for paints or other coatings.
Step 5
Write balanced half-equations for the reactions that occur at the two electrodes.
Answer
At the anode:
ightarrow ext{Br}_2 + e^- $$ At the cathode: $$ ext{Pb}^{2+} + 2e^- ightarrow ext{Pb} $$. These equations represent the oxidation of bromide ions and the reduction of lead ions, respectively.Step 6
How is charge transmitted through the molten PbBr2 electrolyte?
Answer
Charge is transmitted through molten PbBr₂ via the movement of ions. Specifically, the lead ions () move towards the cathode while bromide ions () move towards the anode, allowing for the conduction of electric current during electrolysis.