22 Chlorine is bubbled through a cylinder containing aqueous sodium iodide and an immiscible layerof hexane.chlorine gasexcess gas outhexaneaqueoussodium iodideAs the bubbles pass through the cylinder, what is observed in the lower and upper layers?lower aqueous layer upper hexane layerA colourless solution becomes brown colourless liquid becomes colouredB colourless solution becomes brown colourless liquid is unchangedC brown solution becomes colourless colourless liquid becomes colouredD brown solution becomes colourless colourless liquid is unchanged
Question
22 Chlorine is bubbled through a cylinder containing aqueous sodium iodide and an immiscible layerof hexane.chlorine gasexcess gas outhexaneaqueoussodium iodideAs the bubbles pass through the cylinder, what is observed in the lower and upper layers?lower aqueous layer upper hexane layerA colourless solution becomes brown colourless liquid becomes colouredB colourless solution becomes brown colourless liquid is unchangedC brown solution becomes colourless colourless liquid becomes colouredD brown solution becomes colourless colourless liquid is unchanged
Solution
The reaction that takes place when chlorine is bubbled through a cylinder containing aqueous sodium iodide and an immiscible layer of hexane is a halogen displacement reaction. Chlorine, being a more reactive halogen, displaces iodine from sodium iodide. The equation for the reaction is:
Cl2 + 2NaI → 2NaCl + I2
The iodine that is displaced goes into the hexane layer, causing it to become coloured (usually purple). The aqueous layer, which initially contained the sodium iodide, becomes a solution of sodium chloride, which is colourless. Therefore, the correct answer is:
B: The lower aqueous layer (sodium iodide solution) becomes brown (due to the formation of sodium chloride), and the upper hexane layer (initially colourless) becomes coloured (due to the presence of iodine).
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