Question #60418

1 Answer
Nov 3, 2015

Answer:

#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#)