Question

Assuming standard conditions, answer the following questions. (Use the table of Standard Reduction Potentials for common Half-reactions from your text. If hydrogen is one of the reagents, assume acidic solution.)

1) Is Cr3+(aq) capable of oxidizing Fe2+(aq) to Fe3+(aq)?

2) Is Cr metal capable of reducing Fe2+(aq)?

3) Is Sn metal capable of reducing Fe3+(aq) to Fe2+(aq)?

4)Is H2(g) capable of reducing Ni2+(aq)?

5) Is Fe2+(aq) capable of reducing Cr3+(aq) to Cr metal?

6)Is VO2+(aq) capable of oxidizing Fe2+(aq)?

Answer 1

1) Is Cr3+(aq) capable of oxidizing Fe2+(aq) to Fe3+(aq)?

Fe3+ + e− <-> Fe2+ 0.77

Cr3+ + e−<-> Cr2+ −0.42

The reaction:

Fe3+ + e− <-> Fe2+ E = 0.77

Cr2+ <->Cr3+ + e- E = −0.42

From, here, Cr+3 will OXIDIZE and Fe will reduce: therefore the answer is NO

2) Is Cr metal capable of reducing Fe2+(aq)?

Cr3+ + 3 e− <--> Cr(s) −0.74

Fe2+ + 2 e− <-> Fe(s) −0.44

the reaction that occurs spontanously:

Cr(s) <-> Cr3+ + 3 e− E = 0.74

Fe2+ + 2 e− <-> Fe(s) E = −0.44

then, Chromium will reduce Fe+2; answer is YES

3) Is Sn metal capable of reducing Fe3+(aq) to Fe2+(aq)?

Fe3+ + e− <-> Fe2+ E = 0.77

Sn2+ + 2 e− <-> Sn(s) −0.13

this will occurs spontaneously:

Fe3+ + e− <-> Fe2+ E = 0.77

Sn(s) <-> Sn2+ + 2 e− E = 0.13

Sn is being oxidized and reduces Fe, therefore the statement is TRUE

4)Is H2(g) capable of reducing Ni2+(aq)?

Ni2+ + 2 e− <-> Ni(s) −0.25

2 H+ + 2 e− <-> H2(g) 0.0000

then this occurs spontaneously

Ni(s) <-> Ni2+ + 2 e− E = 0.25

2 H+ + 2 e− <-> H2(g) 0.0000

that is, Nickel is reducing, therefore the answer is NO

5) Is Fe2+(aq) capable of reducing Cr3+(aq) to Cr metal?

Cr3+ + 3 e− <--> Cr(s) −0.74

Fe2+ + 2 e− <-> Fe(s) −0.44

the reaction that occurs spontanously:

Cr(s) <-> Cr3+ + 3 e− E = 0.74

Fe2+ + 2 e− <-> Fe(s) E = −0.44

answer is NO, Fe+2 will oxidize Chromium

6)Is VO2+(aq) capable of oxidizing Fe2+(aq)?

VO2+ + 2 H+ + e−<-> V3+ + H2O +0.34

Fe2+ + 2 e− <-> Fe(s) E = −0.44

this will occur spontaneously

VO2+ + 2 H+ + e−<-> V3+ + H2O +0.34

Fe(s) <->Fe2+ + 2 e−    E = +0.44

then, the answer is YES; VO+2 will oxidize Fe