Question

(a) What is the displacement reaction?
(b) Identify A in the following reactions.
(i) \[Zn + CuS{O_4} \to A + Cu\]
(ii) \[N{a_2}S{O_4} + BaC{l_2} \to A + 2NaCl\]

Answer 1

Hint:
(i) Displacement reactions are redox reactions in which metal acts as a reducing agent.
(ii) Both the reactions are displacement reactions.


Complete step by step solution:
(a) Displacement reaction is a type of reaction in which one atom of reactant gets displaced by another atom of other reacting species.
e.g. A + B-C \[ \to \] B + A-C
- Generally the more reactive atom displaces relatively less reactive atoms.
- This reaction is a type of a redox reaction in which a metal is used as a reducing agent.

(b) (i) \[Zn + CuS{O_4} \to A + Cu\]
Now, we will need to find A in this reaction.
- This is a displacement reaction in which Zinc replaces Copper from copper sulfate.
- If we don’t know that it is a displacement reaction, we can simply compare the left and right hand side of the reactions and find the unknown compound by adding remaining atoms.
- We can see that one Zinc atom and sulfate ion is present in the left hand side but not present in the right hand side. So, Zinc sulfate will be the unknown compound.
So, A is \[ZnS{O_4}\].

(ii) \[N{a_2}S{O_4} + BaC{l_2} \to A + 2NaCl\]
- This is also a displacement reaction and Barium in Barium chloride replaces Sodium metal from Sodium sulfate.
- If you don’t know this, then we can simply observe that sulfate ions and barium ions are not present in the right hand side while they are present at the left hand side. So, unknown species will be Barium sulfate.
- So, B is \[BaS{O_4}\].


Note: (i) Remember that if less reactive metal will react with the solution of more reactive metal, then displacement reaction will not occur.
e.g.\[Cu + ZnS{O_4} \to \times \]
(ii) Take consideration of oxidation states of metals and write the resulting compounds corresponding to it.