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Question
The chemical reaction between two substances is characterised by a change in colour from orange to green. These two substances are most likely to be ______.
Options
potassium dichromate solution and sulphur dioxide
potassium permanganate solution and sulphur dioxide
potassium permanganate solution and lemon juice
potassium dichromate solution and carbon dioxide
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Solution
The chemical reaction between two substances is characterised by a change in colour from orange to green. These two substances are most likely to be potassium dichromate solution and sulphur dioxide.
Explanation:
Potassium dichromate (K2Cr2O7) is an oxidising agent that naturally forms a bright orange solution due to its dichromate ions. When sulphur dioxide (SO2) gas is passed through it, a redox reaction occurs where the sulphur dioxide acts as a reducing agent. This reduces the chromium ions from an oxidation state of +6 (orange) to +3 (green), turning the entire solution green.
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