Question

A : NaOH cannot be stored in a vessel of Al or Zn.
R : A protective oxide layer is formed on surface

Answer 1

Hint: A redox reaction occurs when sodium hydroxide reacts with metals like aluminum or zinc. Hydrogen atoms undergo reduction in the reaction between sodium hydroxide and metals.

Complete Step-by-Step Solution:
We can see that assertion and its reason is given in the question. We need to find out whether the assertion is true or false and also find whether the reason is correct for assertion or not.
- We know that NaOH is known as sodium hydroxide. In this compound, sodium atom is positively charged and hydroxide ion is negatively charged.
- Aluminum and Zinc are metals. Metals are in zero oxidation state when they are in their metallic form. So, they have a tendency to get oxidized.
- Here, we need to find whether NaOH can react with Al or Zn metal or not. If NaOH does not react with Al or Zn, then we can keep NaOH in the vessel made up of Zn or Al.
- Actually, NaOH reacts with Al or Zn metal to form their corresponding sodium aluminate and sodium zincate respectively. The reaction can be given as below.
\[2Al + 6NaOH \to 2N{a_3}Al{O_3} + 3{H_2}\]
\[Zn + 2NaOH \to N{a_2}Zn{O_2} + {H_2}\]
- So, we can see that as the reaction occurs between NaOH and metal, we cannot keep it in its vessel.
- The reason is given that a protective oxide layer is formed on the surface of metal. This hasn’t occurred here as we can see in the reaction.

So, we can conclude that the assertion given is correct but reason is not correct.

Note: Note that metals have a tendency to lose electrons and become cations. When they are in metallic form, their oxidation number is zero. So, metals have a tendency to undergo oxidation. So, they can act as reducing agents.