Why does zinc increase in weight after being placed in NaOH?

1 Answer
anor277
Jun 11, 2017

Of course the mass of zinc does not increase........

Explanation:

However, zinc, as an active metal, can be OXIDIZED in basic solution as well as acidic solution........to give the "zincate salt", Na_2[Zn(OH)_4]

"Oxidation:"

Zn(s) +4HO^(-) rarr Zn(OH)_4^(2-)+2e^(-) (i)

"Reduction:"

H_2O(l) +e^(-) rarr 1/2H_2(g) + HO^- (ii)

And we take (i)+2xx(ii):

Zn(s)+2H_2O(l) +2HO^(-) rarr Zn(OH)_4^(2-)+ H_2(g)uarr

You could presumably isolate the zincate ion as its sodium salt, Na_2[Zn(OH)_4], which complex has clearly a greater mass than the metal equivalent.

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