Relative half cell potentials

Question

Assuming standard conditions, answer the following questions.

If hydrogen is one of the reagents, assume acidic solution.

a. Is Fe2 (aq) capable of reducing Sn2 (aq) to Sn metal?

b. Is VO2 (aq) capable of oxidizing Fe2 (aq)?

c. Is Cr3 (aq) capable of oxidizing Fe2 (aq)?

d. Is H2(g) capable of reducing Ag (aq)?

e. Is Cr3 (aq) capable of oxidizing Fe2 (aq) to Fe3 (aq)?

f. Is Fe3 (aq) capable of oxidizing Sn metal to Sn2 (aq)?

Any help would be so helpful!

Answer 1

Look up the standard reduction potentials in a table.  The one in the source reference is a good one, but your book probably has one also.  Change sign of the species that is oxidized (in answser a for example, Fe2+ is oxidized to Fe3+, so reverse the sign of that reaction from the table value of +0.771 V to -0.771 V).  Then, if

E0 = E0red + E0ox >0,

the reaction will go.  Be sure to change the sign to get E0ox from the E0 value given in the table.

The reactions for which E0 > 0 are b, d, and f.

Make sure you gave the choices correctly.  Answers c and e are essentially the same.