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 thr form of a table given below:

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

Explanation

The student A had recorded the correct observations in all the four beakers.
• In beaker I, zinc is not in a position to displace aluminium metal, since it is placed below it. Therefore, the solution would remain colourless.
• In beaker II, zinc is in contact with `ZnSO_(4)`. Therefore, no chemical reaction is possible. The solution would remain colourless.
• In beaker III, zinc would displace iron present in ferrous sulphate solution (light green) to form zinc sulphate which is colourless.
• In beaker IV, zinc would displace copper from copper sulphate solution (blue) to form zinc sulphate which is colourless.
From the above discussion, it is quite clear that the student A had made correct observations initially and also after the experiment.