Redox Reactions

Question 1

State the FULL equation when Fe2+ is oxidised to Fe3+ by ACIDIFIED POTASSIUM MANGANATE(VII) solution (KMnO4)

State the colour change.

Answer 1

MnO4- + 8H+ + 5Fe+ →Mn2+ + 4H2O + 5Fe3+

Colour change: Pale Green to Yellow

Question 2

State the FULL equation when Fe3+ is reduced to Fe2+ by Iodide ions, I- (aq).

State the colour change.

Answer 2

2I- + 2Fe3+ → 2Fe2+ + I2

Colour change: Yellow to Pale Green

Question 3

State the FULL equation when Cr3+ (in [Cr(H2O)6]3-) is oxidised to Chromate(VI) solution (CrO4-) by warming Hydrogen Peroxide solution (H2O2) in ALKALINE conditions.

Answer 3

3H2O2 + 2Cr(OH)6 3- → 2OH- + 2CrO4 2- + 8H2O

Question 4

State the FULL equation when you add sulfuric acid to the Chromate(VI) solution.

State the colour change.

Answer 4

2CrO4 2- + 2H+ → CrO72- + H2O

Colour change: Green (Cr3+) to Orange

Question 5

State the FULL equation when Cr2O7 2- is reduced to Cr3+ by Zinc in ACIDIC conditions.

State the colour change.

Answer 5

Cr2O7 2- + 14H+ + 3Zn → 2Cr3+ + 7H2O + 3Zn2+

Colour change: Orange to Green

Question 6

State the FULL equation when Cu2+ is reduced to the Copper(I) Iodide.

State the colour change.

Answer 6

2Cu2+ + 4I- → 2CuI (s) + I2 (aq)

Colour change: Blue solution to White Precipitate (CuI) and Brown/Yellow Solution (I2)

Question 7

State the FULL equation when Cu+ is both oxidised and reduced to form Cu and Cu2+.

State the colour change.

What type of reaction is this?

Answer 7

Cu+ → Cu + Cu2+

Colour change: Light brown/yellow solution to Red-Orange metal Cu) and Pale Blue solution (Cu2+)

Type of reaction: Disporportionation