Question

Aluminium sulphate and copper sulphate solutions were taken in two test tubes I and II respectively. Iron filings were then added to both the solutions. The four students A, B, C and D recorded their observations in the form of a table as given below.

Student	Aluminium sulphate solution (I)	Copper sulphate solution (II)
A	Colourless changes to light green	Blue colour of the solution is retained
B	Colour of colourless solution does not change	Blue colour of the solution changes to light green
C	Colourless solution changes to light blue	Blue colour of the solution changes to colourless
D	Colour of colourless solution remains unchanged	Blue colour of the solution fades away

The correct set of observations have been recorded by the students :
(1) A
(2) B
(3) C
(4) D

Answer 1

In test tube I, an iron filling is added in a solution containing aluminium sulphate solution, no colour change will be observed as iron is not much reactive than aluminium, so it cannot displace aluminium from aluminium sulphate. So, no reaction takes place.
In test tube II, an iron filling is added in a solution containing copper sulphate solution, blue colour changes to light green. As iron is more reactive than copper, so it can displace aluminium from aluminium sulphate.

$3\mathrm{Fe}\left(\mathrm{s}\right)+{\mathrm{Al}}_2\left({\mathrm{SO}}_4{)}_3\right(\mathrm{aq})\to 3{\mathrm{FeSO}}_4(\mathrm{aq})+2\mathrm{Al}(\mathrm{s})$

Therefore, the observations made by student "B" are correct.

Hence, the correct answer is option 2.