Question

Question #60418

Answer 1

`Zn^@` + `2NaOH` + `2H_2O` `rarr` `Na_2Zn(OH)_4` + `H_2` (redox reaction)

Explanation:

Based on the metal activity series, zinc is not active enough to replace the `Na` atom in the solution. So there should be no visible reaction.

`Zn^@` + `2NaOH` `!=` `Zn(OH)_2` + `2Na`
http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/ions/electrolysisrev2.shtml

But laboratory results tells us otherwise because zinc (along with aluminum, copper, tin, lead, and beryllium) is considered as amphoteric, a molecule which reacts to bases and acids alike.

Also, the reaction is not an acid-base, as one might expect but more of an oxidation-reduction reaction with the following half-equations:

Oxidation: `Zn` (`s`) `rarr` `Zn^"2+"` (`aq`) + `2e^–`

Reduction: `Zn(OH)_4^"2-"` (`aq`) + `2e^-` `rarr` `Zn` (`s`) + `4OH^-`(`aq`)