Question
Question: Given; \[{E^ \circ }_{C{u^{2 + }}/Cu} = 0.34V\], \[{E^ \circ }_{Z{n^{2 + }}/Zn} = - 0.76V\] , \[{E...
Given;
E∘Cu2+/Cu=0.34V, E∘Zn2+/Zn=−0.76V , E∘Ag+/Ag=0.80V
Assertion : Copper sulphate solution can be stored in silver vessels.
Reason : E∘cell is positive.
(A) Both assertion and reason are true and reason is the correct explanation of assertion.
(B) Both assertion and reason are true but reason is not the correct explanation of assertion.
(C) Assertion is true but reason is false.
(D) Assertion if false but reason is true.
(E) Both assertion and reason are false.
Solution
Formula to find standard potential of cell is E∘cell=E∘cathode−E∘anode
In the reaction of metal and other metal’s solution, the metal that has higher reduction potential, gets reduced and gets deposited at cathode.
Complete answer:
The reduction potentials of relative metals show its ability to get reduced.
We can see that the reduction potential of Silver is higher than copper, so we can say that silver cannot reduce copper from its solution because silver itself has high reduction potential.
So, assertion is a true sentence.
Now, let’s find E∘cell of this reaction. Note that cell representation can be given by
Ag/Ag+∥Cu2+/Cu
We know that E∘cell=E∘cathode−E∘anode
E∘cell=0.34−0.80
E∘cell=−0.46V
So, E∘cell for this cell is not positive.
Hence, reason is not true.
So, the correct answer for this question is (C) Assertion is true but reason is false.
Additional Information:
Suppose if reverse scenario was there given in the question, that if Silver solution can be stored in copper vessel or not, then the answer would be ‘NO”. This is because silver has higher reduction potential out of them two and will have a tendency to get reduced and will oxidise the copper metal from the vessel.
Note:
Do not forget the minus sign in the formula of the standard potential of the cell. Do not assume standard potential values as their oxidation potentials because they are their respective values of reduction potentials.