Thiosulphate / Manganate titrations

Thiosulphate and iodide are usually used to find concs of what 2 ions?

Cu²⁺ or ClO^-

Reaction of Cu²⁺ with I^-

2Cu²⁺ + 4I^- → 2CuI + I₂

Reaction of ClO^- with I^-

ClO^- + 2H⁺ + 2I^- → Cl^- + I₂ + H₂O

Reaction of thiosulphate with Iodine

2S₂O₃^2- + I₂ → S₄O₆^2- + 2I^-

What indicator can be added to find end point and what is the colour change

Starch solution

Blue → Colourless

Manganate or Dichromate can oxidise what two ions?

Fe²⁺ and C₂O₄^2-

Fe²⁺ oxidation half eq

Fe²⁺ → Fe³⁺ + e^-

C₂O₄^2- oxidation half eq

C₂O₄^2- → 2CO₂ + 2e^-

MnO₄^- Reduction half eq

MnO₄^- + 8H⁺ + 5e^- → Mn²⁺ + 4H₂O

MnO₄^- to Mn²⁺ colour change

Purple → Pale pink

Dichromate reduction half eq

Cr₂O₇^2- + 14H⁺ + 6e^- → 2Cr³⁺ + 7H₂O

Cr₂O₇^2- to Cr³⁺ colour change

Orange → Green