Question

Zinc reacts with excess of caustic soda to form:
A. $Zn{(OH)_2}$
B. $ZnO$
C. $N{a_2}Zn{O_2}$
D. $Zn{(OH)_2}.ZnC{O_3}$

Answer 1

According to the question, first we should check the reaction between zinc and the excess of caustic soda. And then check the product given by them. The product is likely that aqueous zincate solutions consist of mixtures. The solution may be prepared by dissolving zinc, zinc hydroxide, or zinc oxide in an aqueous solution of sodium hydroxide.

Complete answer:
When zinc reacts with the excess of caustic soda or Sodium Hydroxide then it forms Sodium Zincate ($N{a_2}Zn{O_2}$) with hydrogen evolved .
$Zn(s) + NaOH(aq) \to Na{}_2Zn{O_2} + {H_2}$
In the above reaction, Zinc reacts with Sodium Hydroxide which is in aquos form gives Sodium Zincate with evolving of hydrogen. Here, zincate is a negatively charged anion because any element with the Sodium always negatively charged. In the naming of inorganic compounds zincate is a suffix that indicates that a polyatomic anion contains a central zinc atom.
For metals we just say that some of them (such as Zn) dissolve both in acids and in bases. The point is that Zn does not react as an acid in the reaction above since the reaction is not an acid-base one, but rather oxidation-reduction. So, the answer then is that Zn reacts with aqueous solution of sodium hydroxide because it can be oxidized in these conditions in accordance with the reaction mentioned.

So option C is the correct answer.

Note:
Sodium and Potassium always have negatively charged other elements with them. And here in the above reaction the valency of zinc is negative, anion.