5.2.3 - Redox & electrode potentials

Delocalised e- goes on the products side

Delocalised e- goes on the reactants side

Add H2Os to balance oxygens H+ to balance H’s

Add H2Os to balance oxygens OH- to balance H’s

Balance delocalised e- then combine the two Delocalised e- should cancel

Involves transfer of e- from one species to another Titrations of an oxidising agent against a reducing agent

Purple potassium manganate is in the burette Sample analysed is in the flask with an excess of dilute sulfuric acid As the MnO4- ions react, they form Mn 2+ ions which are colourless

MnO4- would oxidise Cl- to Cl2 and then affect the vol of KMnO4 required in the titration

They are oxidising agents themselves so affect the vol of KMnO4 required

It’s a weak acid and would not provide enough H+ ions

5:1

Oxidised w/ H2SO4 to Fe (2+) ready for analysis

Reacted w/ Zn to reduce it to Fe (2+)

2.5 : 1

Ethanedioate ion

Titration that does not need an indicator

A reaction where one of the products acts as a catalyst

As both ions are -ve they repel each other and the reaction is slow and needs warming at the start However Mn2+ acts as a catalyst and speeds up reaction

2 Cu2+ + 4I- —-> 2CuI + I2 CuI - white ppt

2 I- + ClO- + 2H+ —> Cl- + I2 + H2O

2 S2O3 + I2 —> 2 I- + S4O6 2-

2:1

1:1

2:1