Is the dissolution of a solid metal in an acidic solution an example of a #"redox reaction?"#

1 Answer
Jan 3, 2017

Answer:

#Zn(s) + 2HCl(aq) rarr ZnCl_2(aq) + H_2(g)uarr#

The metal is oxidized, and the hydrogen ion is reduced.

Explanation:

For the oxidation of #"Zn"#:

#Zn(s) rarr Zn^(2+) + 2e^-#; #"oxidation (i)"#

For the reduction of #"hydronium ion"#:

#H^(+) + e^(-) rarr 1/2H_2(g)#; #"reduction (ii)"#

We add these equations together such that electrons do not appear in the equation: #(i) +2xx(ii):#

#Zn(s) +2H^(+) rarr Zn^(2+) + H_2(g)uarr#

We would repeat this for iron metal and sulfuric acid, except that sulfuric acid is a non-oxidizing acid under normal circumstances, and the question SHOULD have been asked with respect to hydrochloric acid or nitric acid. Iron filings will react with #HCl# in precisely the same stoichiometry as zinc:

#Fe(s) + 2HCl(aq) rarr FeCl_2(aq) + H_2(g)uarr#