Question

Assuming standard conditions, answer the following questions.
(If hydrogen is one of the reagents, assume acidic solution.)

a) Is Fe²⁺(aq) capable of oxidizing Cr metal?
b) Is H₂(g) capable of reducing Ni²⁺(aq)?
c) Is Cr³⁺(aq) capable of oxidizing Fe²⁺(aq) to Fe³⁺(aq)?
d) Is H₂(g) capable of reducing Ag⁺(aq)?
e) Is Fe²⁺(aq) capable of reducing VO₂⁺(aq)?
f) Is Sn²⁺(aq) capable of oxidizing Fe²⁺(aq)?

I got yes, no, no, yes, no, no but it's wrong.
Guidance & help for this question would be greatly appreciated.
Thanks!

Answer 1

Cr³⁺ + e^- Cr²⁺                          -0.42V

Cr Cr³⁺ + 3e^-                           +0.74V

Fe²⁺ Fe³⁺ + e^-                         +0.77V

VO²⁺ 2 H⁺ +  e⁻ V³⁺ + H₂O        +0.34V

H₂ 2H⁺ + 2e^-                            +0V

Ag⁺ + e^- Ag                         +0.7996V

Ni²⁺ + 2e^- Ni                        -0.25V

Sn²⁺ + 2e^- Sn                         -0.13V

a) This can happen, because Fe²⁺ has a higher potential than Cr, so Fe²⁺ can be reduced (this would need to happen for Fe²⁺ to oxidize Cr).

b) Ni²⁺ potential is lower than H₂ so Ni²⁺ cannot be reduced.

c) This cannot happen, because Cr³⁺ has a lower potential than Fe²⁺, so Cr³⁺ cannot be reduced (this would need to happen for Cr³⁺ to oxidize Fe²⁺).

d) Ag⁺ potential is higher than H₂ so Ag⁺ can be reduced.

e) This cannot happen, because the standard potential of VO²⁺ is lower than that of Fe²⁺, so VO²⁺ cannot be reduced.

f) This cannot happen, because Sn²⁺ has a lower potential than Fe²⁺, so Sn²⁺ cannot be reduced (this would need to happen for Sn²⁺ to oxidize Fe²⁺).