Four students A, B, C and D noted the initial colour of the solutions in beakers I, II, III and IV. After inserting zinc rods in each solution and leaving it undisturbed for two hours, noted the colour of each solution again.

They recorded their observations in the form of a table given below:

Student	Colour of the solution	I	II	III	IV
A	InitialFinal	ColourlessColourless	ColourlessColourless	Light greenColourless	BlueColourless
B	InitialFinal	ColourlessColourless	Light yellowColourless	Light greenLight green	BlueColourless
C	InitialFinal	ColourlessLight blue	ColourlessColourless	Light greenColourless	BlueLight blue
D	InitialFinal	Light greenColourless	ColourlessColourless	Light greenDark green	BlueColourless

Which student noted the colour change in all the four beakers correctly?"

Correct answer: The observation made by student A is correct.

Explanation:

1. For beaker I, the zinc rod is dipped in aluminium sulphate, as zinc is less reactive than aluminium so, no reaction will take place.
2. For beaker II, the zinc rod is dipped in zinc sulphate, no reaction takes place as the zinc rod is dipped in zinc solution.
3. For beaker III, zinc rod is dipped in ferrous sulphate, as zinc is more reactive than ferrous sulphate (light green), it reacts with zinc to produce zinc sulphate (colourless).
4. For beaker IV, the zinc rod is dipped in copper sulphate (light blue), as zinc is more reactive than copper sulphate it reacts with zinc to produce zinc sulphate (colourless).

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Updated on: 10-Oct-2022

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