redox reactions, oxi num, activity series

in some reactions, electrons are transferred, like in precipitation reactions

oxidation half equation

• electrons being donated (electrons removed from the LHS atom)

• phase of electrons doesn’t matter

• reductant is on the LHS

• keep the stoichiometric ratios of the net ionic equation

reduction half equation

• electrons being given/accepted (electrons added to the LHS atom)

• phase of electrons doesn’t matter

• oxidant is on the LHS

• keep the stoichiometric ratios of the net ionic equation

oxidation

• increase in the oxidation number

• less e increases the oxidation number

• atom thus loses e

reduction

• reduction in the oxidation number

• more e reduces the oxidation number

• atom thus gains e

redox reaction is composed of:

an oxidation half equation, a reduction half equation

oxidation or reduction nmeonic + meaning

OIL RIG

oxidation is loss of e

reduction is increase of e

oxidation is increase in oxidation state
reduction is reduction in oxidation state

reductant/reducing agent

• facilitates reduction by donating e/losing e and giving it to other

• undergoing oxidation/ is in oxidation half equation

oxidant/oxidising agent

• facilitates oxidation by being available to accept e/being an ion

• undergoing reduction/ is in reduction half equation

H₂O_(l) can be split into:

H⁺_(aq) + OH^-_(aq)

• dont try find out why

finding half equations (2 methods)

• ‘reduction in o.s. = reduction reaction’, no change in o.s. = spectator ion

  • draw oxidation states below, and arrows to non-spectator before and after.

  • if increase in oxidation state, oxidation

• oxidise means gain oxygen, or lose hydrogen

oxidation state (9). 3 general, 3 for groups, 3 element specific

General Rule

1. elements: (Na, O2): O.N. = 0

2. for ion, O.N. = ion charge

3. sum of O.N.

   1. neutral compound, = 0

   2. polyatomic ion, = charge

Rules for Specific Groups

1. group 1, +1 in ALL COMPOUND

2. group 2, +2 in ALL COMPOUNDS

3. group 17, -1 unless with oxygen which is -2 or more electronegative elements who take the -1

Element Specific

1. fluorine is always -1

2. hydrogen, +1 with non-metals

   • -1 with metals (?)

3. oxygen: usually -2, but -1 in peroxide

displacement reaction:
- who displaces who?

• the more reactive element displaces the less reactive element

• less reactive must be dissolved

‘mnemonic’ to remember who displaces who

more reactive stays dissolved in solution

• if the more reactive metal is the one in the acid, no reaction occurs

• if it isn’t, the metal is displaced and forms around the sample of the more reactive metal (reaction has to happen somewhere)

reactivity series reaction order (most to least reactive)

• metal and water & metal w O₂ to form peroxide

  • Kangaroos Bake Cakes N_eatly

• metal and water

  • Mg, Al, Zn, Cr, Fe

• metal and acid

  • Co, Ni, Sn, Pb

all above react with O₂. Cu will too.

• no reaction (no matter what help u try do)

  • Platinum Sells at Auctions (Pt, Ag, Au)

metal and O₂ metals

K, Ba, Ca, Na

kangaroos bake cakes neatly

metal and water

metal and hot water

metals

Mg, Al, Zn, Cr, Fe

Magnesium Allows Zinc to Cover Rusty Iron

metal and acid

metal and hot acid

metals

Ni, Sn, Pb

Nickel Shields Tin-Plated Batteries

no reaction metals

Cu, Hg, Ag, Pt, Au

copper’s heavy,

auctions sell platinum or A Giant Protects Australia

mnemonic for all elements in activity series from most to least reactive (18)

"King BaCa Naively Made(Mg) All Zebras(Zn) Cry(Cr), Feisty Nickel Snakes Pounced(Pb). Curious Hounds(Hg) Aggressively Pursued(Pt) Antelopes(Au)."

js look at activity series and pray it’s on there