Question

Find the products: Zn + NaOH \to \\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_\\_

Answer 1

Hint: Zinc metal acts as a reducing agent. Reducing agents themselves get oxidized and reduce other species. Sodium hydroxide is a base. Zinc is less reactive metal than sodium.

Complete step by step solution:
Sodium hydroxide is a base and zinc metal is a reducing agent.

- Zinc metal is not just a reducing agent but is also a transition metal as well.

- Here, we can think that a displacement reaction may occur. But this reaction will not occur because zinc needs to have more oxidation potential than sodium in order to give a displacement reaction. In other words we may say that more reactive metal will replace the less reactive metal but here the more reactive metal is in the compound only. So, the displacement reaction will not take place.

- But only some metals have characteristics to react with base as well. Zinc and aluminum react with base to give similar products.

- In this reaction, actually as zinc is a reducing agent but it cannot reduce sodium metal, hence it reduces hydrogen atoms from the NaOH and produces hydrogen gas. Sodium Zincate ($N{a_2}Zn{O_{2(s)}}$) is the main product in this reaction. The overall reaction can be given as below.

$Zn + 2NaOH \to N{a_2}Zn{O_{2(s)}} + {H_{2(g)}}$

- So, as we can see that the oxidation number of hydrogen atoms in sodium hydroxide is +1 and it gets reduced to zero in hydrogen gas. Zinc metal acts as a reducing agent and gets oxidized from zero to +2 oxidation state. So, this is a redox reaction.

Note: Do not consider this reaction as a displacement reaction as zinc is less reactive metal than sodium metal. It is not necessary that when metal reacts with a compound, it can give only displacement reactions only. It can give different reactions also according to their reactivity.