Topic 3 Redox reactions Flashcards
Oxidation number
The charge that an ion has or the charge that it would have if the species were fully ionic.
Oxidation (in terms of oxidation number)
Oxidation results in an increase in oxidation number.
Reduction (in terms of oxidation number)
Reduction results in a decrease in oxidation number.
Oxidation number rules: element
An element in its elemental form is always zero (O2, N2, Fe, Na).
Oxidation number rules: compound
The sum of the oxidation numbers is a neutral compound must equal zero (NH3).
Oxidation number rules: ion
The sum of the oxidation numbers in an ion must equal the charge on the ion.
Oxidation number rules: electronegativity
The more electronegative element is given the negative oxidation number (NH3, CH4).
Oxidation number rules: hydrogen
The oxidation number of hydrogen is nearly always +1 except in hydrides when it -1
Oxidation number rules: oxygen
The oxidation number of oxygen is nearly always -2 except in peroxides when its -1 and when in a compound with fluorine its positive.
Oxidation number rules: fluorine
The oxidation number of fluorine is always -1
Oxidation equation example
Mg —> Mg2+ + 2e
Reduction equation example
Cl2 + 2e —> 2Cl-
Disproportiation
A simultaneous occurrence of oxidation and reduction of the same element in a single reaction.
Oxidising agent
A species that oxidises another species by removing one or more (of their) electrons. When an oxidising agent reacts it gains electrons and is therefore reduced.
Reducing agent
A species that reduces another species by adding one or more electrons. When a reducing agent reacts it loses electrons and is therefore oxidised.
