GCSE Chemistry Revision Notes (all the hard stuff)

Chemistry

Electrolysis

-Anode - + - non-metal (anions)

-Cathode - - - metal (cations)

-In an aqueous solution with a reactive metal (Al or G1, G2 element) hydrogen is given at the cathode instead of the metal --> in order to extract the metal solution must be molten, not dissolved

-Less reactive metals can be extracted with Carbon

-In an aqueous solution with a complex non-metal ion (eg SO4, NO3), O2 is given at the anode

4OH- + 4e- -->2H2O + 2O2

-Active electrodes (made of metal) - the anode's loss is the cathode's gain

Salts equations

Note: An alkali is a base that will dissolve in water

All metal oxides are bases. Some are alkalines.

A Salt is any metal compound that can be made from acids

Usually takes the form metal+halogen

H+ (aq) Ions make a solution acidic.

Acid + Base --> Salt + water

HCl + KOH --> KCl + H2O

Acid + Carbonate --> Salt + water + Carbon dioxide

2HCl + MgCO3 --> MgCl2 + H2O + CO2

Acid + Metal --> Salt + Hydrogen

HCl + Li --> LiCl + H

Precipitation

Salt Solubility

-Cl Soluble (except with Pb, Ag)

-SO4 Soluble (except with Ba, Ca, Pb)

-NO3 Soluble

Li-, Na-, K- -All soluble

A precipitation reaction takes the form AB (aq) + CD (aq) --> AD (s) + CB (aq)

Ions C and B do not change state.

ION Ochard

Brass knuckles with wing

English: aqueous solution of chromium(II) acetate

These are the spectator ions.

Testing salts

Type of salt (ion) Test Precipitate colour

Cl AgNO3 White (AgCl)

Br AgNO3 Cream (AgBr)

I AgNO3 Pale yellow (AgI)

SO4 BaNO3 White (BaSO4)

Flame Tests

Li - Red

Na - Yellow

K - Purple

Ca - Brown

Ba - Green

Cu - Turquoise

R

Y

PB T

G

RYP BG T

Other test...