Question

What would you observe when Zinc is added to a solution of Iron (II) sulphate? Write a chemical reaction that takes place.

Answer 1

Hint: When zinc is added to Iron (II) sulphate solution there is some chemical reaction that takes place between zinc and iron. Reaction depends on the basis of their reactivity. Let us find it out by help of one chemical reaction.

Complete answer:
Consider a general reaction between two metals:
$A - B + C \to A - C + B$
This happens only when C is more reactive than B.
This is a type of Displacement reaction. Here zinc metal is more reactive than Fe. So zinc displaces other metals easily.
So a displacement reaction is a chemical reaction in which one element is replaced by another element in a chemical reaction.
$Zn + FeS{O_4} \to ZnS{O_4} + Fe$
Therefore, Zn displaces Fe from its solution.
When zinc is added to $FeS{O_4}$ solution, color changes from green to colorless.
$FeS{O_4}$ is green in color and $ZnS{O_4}$ solution is formed and greyish black iron metal is deposited.
This is a single displacement reaction. In this reaction color change takes place but no precipitate is formed.


Additional Information: Another type of reaction is double displacement reaction. In this reaction metal displaces each other from their solution.
Example: $NaCl + AgN{O_3} \to NaN{O_3} + AgCl \downarrow $

Here we see that sodium and silver displace each other and precipitate of AgCl is formed.

Note: Displacement reaction has many applications. Some of them are thermite welding, steel making, extraction of metal and relief from acid indigestion. Generally a single displacement reaction is exothermic. We use the ‘’activity series’’ table to know whether displacement occurs or not.