How do we use redox potentials to predict the reactivity of acids with metals?

1 Answer
May 8, 2016

Answer:

Hydrochloric acid will oxidize zinc metal. It will not oxidize copper metal.

Explanation:

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

So how do you know? Well you turn to a handy redox potential:

#Zn^(2+) + 2e^(-) rarr Zn(s)# #; E^@=-0.76V#

#Cu^(2+) + 2e^(-) rarr Cu(s)# #; E^@=+0.34V#

#H^+ + e^(-) rarr 1/2H_2(g)# #; E^@=+0.0V#

Because, the reduction potential of zinc ion is negative, the oxidation reaction, the reverse reaction, has a positive #E"^@# value., which is thermodynamically viable (i.e. #DeltaG^@=-nFE^@#).

According to this, hydrochloric acid should oxidize those metals whose redox potentials are negative.