Question

Reaction of Zn(OH)₂ with NaOH produces
(A) Na₂ZnO₂
(B) ZnO
(C) Na₂O
(D) None of these

Answer 1

Hint :Hydroxide of zinc Inorganic chemical compound Zn(OH)₂. Wülfingite (orthorhombic), ashoverite, and sweetite are three rare minerals that contain it (both tetragonal). Zinc hydroxide (and Zinc oxide) is amphoteric, like the hydroxides of other metals such as lead, aluminium, beryllium, tin, and chromium. As a result, it dissolves readily in a dilute solution of a strong acid, such as HCl, as well as an alkali solution, such as sodium hydroxide.

Complete Step By Step Answer:
Hydroxide of zinc Inorganic chemical compound Zn(OH)₂. Wülfingite (orthorhombic), ashoverite, and sweetite are three rare minerals that contain it (both tetragonal). Zinc hydroxide (and Zinc oxide) is amphoteric, like the hydroxides of other metals such as lead, aluminium, beryllium, tin, and chromium. As a result, it dissolves readily in a dilute solution of a strong acid, such as HCl, as well as an alkali solution, such as sodium hydroxide.
The inorganic compound sodium hydroxide, also known as lye or caustic soda, has the formula NaOH. It's a white ionic compound made up of sodium cations Na⁺ and hydroxide anions OH⁻.
 $ Zn{(OH)_2}\; + \;2\;NaOH\; \to \;N{a_2}[Zn{(OH)_4}] $
This is an acid-base (neutralisation) reaction: NaOH is a base, and Zn(OH)₂ is an acid.
This is a complexation reaction, and the generated complex is Na₂[Zn(OH)₄].
If too much sodium hydroxide is added, the zinc hydroxide precipitate dissolves, leaving a colourless zincate ion solution.
This property can be used to detect zinc ions in solution, but it isn't unique because aluminium and lead compounds have similar properties. Unlike aluminium and lead hydroxides, zinc hydroxide forms a colourless, water-soluble ammine complex when exposed to excess aqueous ammonia.
Option (A) is correct answer.

Note :
If too much sodium hydroxide is added, the zinc hydroxide precipitate dissolves, leaving a colourless zincate ion solution.
This property can be used to detect zinc ions in solution, but it isn't unique because aluminium and lead compounds have similar properties. Unlike aluminium and lead hydroxides, zinc hydroxide forms a colourless, water-soluble ammine complex when exposed to excess aqueous ammonia.