Consider a voltaic cell based on the following cell reaction:
Ni(s) + At2(s) —> Ni2+(aq) + 2At– (aq)
Given that the standard cell emf is 0.55 V, what is the standard reduction potential for astatine? [Ecell(Ni2+/Ni) = –0.25 V]
To find the standard reduction potential for astatine (At), we can use the formula:
Ecell = Ereduction (cathode) - Eoxidation (anode)
where Ecell is the standard cell emf, Ereduction is the standard reduction potential for the cathode (Ni2+/Ni), and Eoxidation is the standard oxidation potential for the anode (At/At-).
We are given that Ecell = 0.55 V and Ereduction (Ni2+/Ni) = -0.25 V. We can rearrange the formula to solve for Eoxidation:
Eoxidation (At/At-) = Ereduction (cathode) - Ecell
Eoxidation (At/At-) = -0.25 V - 0.55 V
Eoxidation (At/At-) = -0.80 V
Therefore, the standard oxidation potential for astatine is -0.80 V, which is also the standard reduction potential for astatine since the reaction is reversible.