Question

Give the name of the gas evolved when sodium hydroxide reacts with zinc metal. Write equations also.

Answer 1

Hint: When a base reacts with zinc metal, it forms a metal-zincate and a flammable gas is liberated during the reaction. Bubbles are formed during the reaction which indicates the formation of a gas.

Complete step by step answer:
We know that bases react with metals like zinc and aluminium which leads to the formation of zincate or aluminate along with the evolution of a gas.
When sodium hydroxide is reacted with zinc metal granules, it gives sodium zincate and hydrogen gas is liberated.
We can write the reaction as-
\[Zn(s)+2NaOH(s)+2{{H}_{2}}O\to N{{a}_{2}}Zn{{(OH)}_{4}}(aq)+{{H}_{2}}(g)\uparrow \]
As we can see in the above reaction, when solid zinc metal reacts with 2 moles of sodium hydroxide in presence of water, it gives aqueous sodium zincate and hydrogen gas is liberated.
We can also write the same reaction as-
\[2NaOH+Zn\to 2NaZn{{O}_{2}}+{{H}_{2}}(g)\uparrow \]
Here also the product is the same where sodium hydroxide reacts with zinc to give sodium zincate, which is a salt and hydrogen gas is liberated. This reaction is vigorous and bubbles are formed in the solution when zinc is added and it rises up and bubbles are formed which shows us that a gas is formed.
No heating is required during the reaction. Zinc granules are put directly into a strongly heated solution of sodium hydroxide and it reacts immediately.
As we can understand from the above discussion that hydrogen gas is evolved during the given reaction.

Therefore, the answer is hydrogen gas.

Note: Not all metals react with bases but zinc does due to its amphoteric nature. Zinc oxide is amphoteric i.e. it reacts with both acids and bases. ZnO formed during the reaction makes it possible for the formation of zincate salt when a base is added to it.