A test-tube contains a colourless solution of potassium iodide. The presence of iodine can be tested by:

adding a few drops of blue litmus solution

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adding a few drops of copper sulphate solution

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passing carbon dioxide gas through the solution

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passing chlorine gas through the solution

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Solution

The correct option is D passing chlorine gas through the solution
Chlorine will displace iodine from solution containing potassium iodide since it is more reactive than iodine. The liberated iodine will impart violet colour to the solution.
$2 K I (a q) + C l_{2} (g) \to 2 K C l (a q) + I_{2} (g)$
(violet)

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A test-tube contains a colourless solution of potassium iodide. The presence of iodine can be tested by:

The correct option is D passing chlorine gas through the solutionChlorine will displace iodine from solution containing potassium iodide since it is more reactive than iodine. The liberated iodine will impart violet colour to the solution.2KI(aq)+Cl2(g)→2KCl(aq)+I2(g) (violet)