Question

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

Answer 1

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.