Thursday, February 18, 2010

Balancing REDOX in acids and alkali

OCl- in acid conditions goes to Cl2

2OCl- + 4H+ + 2e- --> Cl2 + 2H2O



OCl- in alkali conditions Cl-

OCl- + 2H+ + 2e- + 2OH- --> Cl- + H2O

OCl- + H2O + 2e- --> Cl- + 2OH-

Wednesday, February 17, 2010

Sunday, February 14, 2010

Standard electrode (reduction) potentials

These are a measure of how easy a REDOX half reaction undergoes reduction and can be used to predict if voltage will be generated for a given combination and can be looked up in a data booklet.
The more positive the Eo value the easier the half reaction will undergo reduction.




Electrochemical cell diagrams


Electrolysis vs Electrochemical cells.

Electrolysis

Copper + Chlorine gas --> copper chloride (spontaneous reaction)

Copper + Chlorine gas <-- Copper chloride (non-spontaneous reaction)
electrolysis


Electrochemical cells

This works by combining two REDOX half cells containing metals of different reactivity.

example: Zn/Zn2+ half cell connected to a Cu/Cu2+ half cell.

When these two half cells are connected, the Zn half cell undergoes oxidation because Zn is more reactive that Cu.

Zinc half cell:

Zn --> Zn2+ + 2e- -this is oxidation, LEOA, anode, and will be negative as electrons are being released.

Copper half cell:

Cu2+ + 2e- --> Cu -this is reduction, GREC, cathode, and will be positive.

Thursday, February 4, 2010

Potassium Permanganate in acid, alkali and neutral conditions

Welcome to Year 13 Chemistry 2010


This blog is set up as a place where we can put tip-bits of information, webcasts and other exciting class experiences that will hopefully be useful when you come to revise.