7.5 Redox

Define redox

oxidation & reduction always occur together

Oxidation
> (gain/loss) oxygen
> (gain/loss) electrons
> (gain/loss) hydrogen
> (up/down) ON

gain, loss, loss, up

Reduction
> (gain/loss) oxygen
> (gain/loss) electrons
> (gain/loss) hydrogen
> (up/down) ON

loss, gain, gain, down

Define oxidation number (ON)

no of e an atom lost/gained

ON of elements e.g. Fe

0

ON of H₂ atoms (in compound) e.g. HCl

+1

Exceptions to H₂: hydrides ON =

hydride -1

ON of O₂ atoms (in compound) e.g. CO₂

-2

Exceptions to O₂: peroxides ON =

peroxide -1

ON of monoatomic ions e.g. Fe²⁺

charge

ON of polyatomic ions e.g. MnO₄^-

sum = charge

ON of molecules e.g. CO₂

sum = 0

Oxidation
Fe²⁺ → Fe^__+ + __

3, e

Reduction
MnO₄^- + 5__ → Mn^__+
(MnO₄^- ON = +7)

e, 2

Oxidising Agent
> subst. __ another (by accepting ē) and is itself __

oxidises, reduced

Reducing Agent
> subst. __ another (by donating ē) and is itself __

reduces, oxidised