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

1 Answer
Jun 11, 2017

Answer:

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.