If iron (Fe(s)/Fe2+(aq)) is used as a reference electrode, what are the new standard reduction potentials for Al(s)/Al3+(aq), Zn(s)/Zn2+(aq), and Ni(s)/Ni2+(aq)?

When a new reference electrode is used, its standard potential is set to 0.00 V. The potentials of all other half-cells are then adjusted relative to this new reference. The formula for the new potential ($E'_{new}$) is:

In this case, iron ($Fe(s) / Fe^{2+}(aq)$) is the reference electrode, and its original standard potential is $E^\circ_{reference} = +0.44$ V (from the given table).

• For $Al(s) / Al^{3+}(aq)$:

  $$E'_{Al} = (-1.66 \text{ V}) - (+0.44 \text{ V}) = -2.10 \text{ V}$$

• For $Zn(s) / Zn^{2+}(aq)$:

  $$E'_{Zn} = (-0.76 \text{ V}) - (+0.44 \text{ V}) = -1.20 \text{ V}$$

• For $Fe(s) / Fe^{2+}(aq)$:

  $$E'_{Fe} = (+0.44 \text{ V}) - (+0.44 \text{ V}) = 0.00 \text{ V}$$

• For $Ni(s) / Ni^{2+}(aq)$:

  $$E'_{Ni} = (+0.25 \text{ V}) - (+0.44 \text{ V}) = -0.19 \text{ V}$$

The rewritten $E^\circ$ values using iron as a reference electrode are: