Question

Four students A, B, C and D took aqueous solutions of zinc sulphate and iron sulphate in two test tubes I and II and dropped metal pieces of Iron and Zinc in the two solutions. After several hours, they made observations and recorded their findings in the form of a table given below:

Observation	Metal	Solution	Change in colour of the solution	Deposit/Residue obtained
By A	Fe	ZnSO${}_4$	turned green	Silver grey coating
	Zn	FeSO${}_4$	no change	no change
By B	Fe	ZnSO${}_4$	no change	black residue
	Zn	FeSO${}_4$	colour faded	grey coating
By C	Fe	ZnSO${}_4$	no change	no change
	Zn	FeSO${}_4$	turned colourless	black residue
By D	Fe	ZnSO${}_4$	no change	grey residue
	Zn	FeSO${}_4$	no change	black reside

Who reported the correct observation?

• A. A
• B. B
• C. C
• D. D

Answer 1

Answer: (C)

C

Observation of student C is correct as Fe cannot displace Zn from its $ZnS{O}_4$ solution. On the other hand, Zn can displace Fe from $FeS{O}_4$ solution to form $ZnS{O}_4$ which is colourless and black coloured residue of Fe is formed. The chemical equation for this reaction can be written as:

$Zn+FeS{O}_4\to ZnS{O}_4+Fe$

Option C is correct.