Question

Which ion is the strongest reducing agent under standard conditions? You should refer to the Eo data table.

Constants
Faraday constant: 9.6485 × 104 C/mol
Nernst factor at 25 oC: 0.0592 V

Standard Reduction Potentials (vs. SHE)
Eo(Ti3+, Ti2+) = -0.90 V
Eo(Zn2+, Zn) = -0.80 V (in Hg)
Eo(Cr3+, Cr(s)) = -0.744 V
Eo(Cr3+, Cr2+) = -0.42 V
Eo(Cu2+, Cu(s)) = +0.339 V
Eo(Fer3+, Fe2+) = +0.771 V
Eo(Hg2+, Hg22+) = +0.908 V

Cr2+

Hg22+

Ti2+

Fe2+

Answer 1

among the four options given Ti+2 is the strongest reducing agent.

A reducing agent is the one which reduces others by giving electrons and oxiidises self.

Let us take each one.

Cr+2 -----------> Cr+3 +e- E0 for this is +0.42V

Hg2+2 -------------> 2Hg+2 + 2e- E0 = -0.98V

Ti+2 -----------> Ti+3 + e- E0 = +0.90V

Fe+2 --------> Fe+3 + e- E0 = -0.771V

The negativ evalues indicate there is little tendency for that reaction to occur.

Thus Hg2+2 and Fe+2 are out.

Among Cr+2 and Ti+2 , Ti+2 has higher positive potential for oxidation of self, that is it has higher potential to give out electrons and thus a better reducing agent.

Thus the answer is Ti+2 is the strongest reducing agent among the given.