Which of the following is an oxidation-reduction reaction? a. hcl(aq) + lioh(aq) → licl(aq) + h2o(l) b. pb(c2h3o2)2(aq) + 2 nacl(aq) → pbcl2(s) + 2 nac2h3o2(aq) c. nai(aq) + agno3(aq) → agi(s) + nano3(aq) d. mg(s) + 2 hcl(aq) → mgcl2(aq) + h2(g)

Option (d) is the correct answer.

Explanation:

A reaction in which there occurs change in oxidation state of reacting species is known as an oxidation-reduction reaction.

(a)    

Will be written as:

In this reaction, there occurs no change in oxidation state of reacting species. Hence, it is not an oxidation-reduction reaction.

(b)  

Will be written as:

Similarly here,  there occurs no change in oxidation state of reacting species. Hence, it is not an oxidation-reduction reaction.

(c)  

Will be written as:

Here, also there occurs no change in oxidation state of reacting species. Hence, it is not an oxidation-reduction reaction.

(d)    

So, here there occurs change in oxidation state of Mg from 0 to +2 and oxidation state of H changes from +1 to 0. Hence, it is an oxidation-reduction reaction.

Thus, we can conclude that is an oxidation-reduction reaction.