Here's the balanced chemical equation:
Zn(NO₃)₂(aq) + 2NaOH(aq) → Zn(OH)₂(s) + 2NaNO₃(aq)
Explanation:
* Formation of Zinc Hydroxide: When zinc nitrate reacts with sodium hydroxide, the hydroxide ions (OH⁻) from NaOH react with the zinc ions (Zn²⁺) from zinc nitrate to form insoluble zinc hydroxide (Zn(OH)₂). This precipitates out of solution as a white solid.
* Sodium Nitrate: The remaining ions, sodium (Na⁺) and nitrate (NO₃⁻), remain in solution as sodium nitrate (NaNO₃), which is soluble.
Excess Sodium Hydroxide:
If excess sodium hydroxide is added, the zinc hydroxide precipitate will further react with the excess hydroxide ions to form the tetrahydroxozincate(II) ion ([Zn(OH)₄]²⁻), which is soluble and remains in solution. This results in the disappearance of the white precipitate.
Overall reaction:
Zn(NO₃)₂(aq) + 4NaOH(aq) → [Zn(OH)₄]²⁻(aq) + 2Na⁺(aq) + 2NO₃⁻(aq)
In summary:
* The reaction of zinc nitrate with a limited amount of sodium hydroxide will produce a white precipitate of zinc hydroxide.
* Adding excess sodium hydroxide will dissolve the zinc hydroxide precipitate, forming a clear solution containing the tetrahydroxozincate(II) ion.
