Redox Reactions Flashcards
Rules for assigning oxidation states
On simple ions it is just their charge. In elements it’s 0. The total of oxidation states must equal the overall charge of the species. In molecules the more electronegative element is assumed to the the negative ion. H is nearly always +1 and O -2.
What is a redox reaction.
A reaction where one species is oxidised and one is reduced.
What is a disproportionation reaction?
A redox reaction where one species is simultaneously oxidised and reduced.
How to balance half equations
To balance oxygens you add water molecules on one side. To balance the hydrogens from this you can only add H+ ions to one side. Check the charge of each side and add electrons to one side if the charge needs balancing.
How to add half equations
To add half equations the number of electrons transferred in each must be equal. Multiply the whole half equations by appropriate numbers to get the coefficient of the electrons equal. Then add these half equations together. The same species on opposite sides (eg H+) can cancel down.
How to derive the half equations from the full equation
Assign oxidation states to see what has been oxidised and reduced. Balance the two half equations of the species oxidised and reduced normally.
