chemistry - redox and electropotentials

Oxidising Agent

A substance that oxidises another species by causing it to lose electrons, being reduced itself as it gains electrons

Reducing Agent

A substance that reduces another species by causing it to gain electrons, being oxidised itself as it loses electrons

Manganate (VII) Titrations (5)

A type of redox titration
MnO4- Oxidising Agent which is Reduced to Mn2+
Fe2+ Reducing Agent which is oxidised to Fe3+
Soln acidified using H2SO4
KMnO4 is self indicating, going from purple to pale pink

Thiosulfate Titrations (4)

A type of redox titration
2S2O3 2- + I2 → 2I- + S4O6 2-
Light brown colour of iodine goes paler as it is converted to colourless iodide ions, starch added to confirm no presence of Iodine
This titration is used to determine concentration of an oxidising agent which oxidises iodide to form iodine, the amount of iodine is determined from a titration against a known quantity of Na2S2O3 soln

Factors affecting electrode potential

Temperature
Pressure of Gases
Concentration of Reagents

Standard Electrode Potential

Potential difference produced when a standard half cell is connected to a standard hydrogen cell under standard conditions

More positive E value

More likely to be reduced

Cathode

Place where reduction occurs

Anode

Place where oxidation occurs

Use of Salt Bridge

Commonly KNO3, used to allow ions to move between half cells to prevent charge build up

Fuel Cells

Use the energy of a reaction between a fuel and oxygen to create a potential difference
Consists of a reaction chamber, outlet for products, electrolyte and semi permeable membrane

Benefits of HFCs (3)

Water is the only product
All bond energy is converted into electrical, no waste in heat or light
No harmful oxides of nitrogen produced

Drawbacks of HFCs (3)

Hydrogen is highly flammable
Production & Storage of H2 is risky
Low Energy Density and Expensive to Produce