Transition metal oxidising/reducing agents

Question 1

Iron Oxidation

Answer 1

Fe2+ –> Fe3+

Reagent: Potassium manganate (VII) - MnO4-

Equation: MnO4- (purple) –> Mn2+ (colourless)

Question 2

Iron Reduction

Answer 2

Fe3+ –> Fe2+

Reagent: Potassium Iodide (KI)

Equation: Fe3+ + 2I- (colourless) –> I2 (brown) + 2Fe2+

Question 3

Reducing Chromium

Answer 3

Cr6+ (orange) –> Cr3+ (green)

Reagent: Iron ions (Fe2+) in acid.

Equation: Cr2O72- (orange) –> 2Cr3+ (green)

(REDUCING FURTHER)
Cr3+ (green) –> Cr2+ (blue)

Reagent: Zinc (s)

Question 4

Oxidising Chromium

Answer 4

Cr3+ (green) –> Cr6+ (yellow)

Reagent: Hydrogen peroxide (H2O2)

Equation: [Cr(OH)6]3- (green) –>CrO4 2-

Half equation for H2O2: H2O2 +2e- –> 2OH-

Question 5

Disproportion of Cu+ ions

Answer 5

Cu2O(s) + H2SO4(aq) –> Cu(s) + CuSO4(aq) + H2O(l)

Oxidation: Cu +1 –> +2 (in CuSO4)

Reduction: Cu +1 –> 0 (in Cu)

Cu(s) = brown solid
CuSO4(aq) = blue solution