Acids, Bases and salts

Acids Bases and Salts

Acids

identified by the presence H+ ions

Metal carbonates

Bases

Identified by presence of OH- ions

Making salts

Metal oxides are bases

soluble hydroxides are alkalies

Acid + Base --> salt

Neutralisation reaction

H+ + OH- -> H2O

Hydrochloic acid -> chloride

Sulphuric Acid -> sulphate

Nitric acid -> nitrate

Titration

The volumes of acid and alkali solutions that react with each other can be measure by titration using a suitable indicator

If the concentration of one of the reactants is known, the results of the titration can be used to find the concentration of the other reactant.

calculating chemical quantities in titrations involving concentrations

step 1 - convert to dm3

e.g. 25cm3 of HCL = 25/1000 = 0.025 dm3

step 2 - Determine the number of moles.

Moles = conc. x volume

step 3 - work out the number of moles of acid using the balanced equation.

step 4 - conc = number of moles / volume

answer = mol/dm3

Soluble salts can be made from acids reacting with them:

metals - not all metals are suitable; some are too reactive and some not enough.

Insoluble bases - the base is added to the acid until no more will react and the excess solid is filtered off.

Alkalis - an indicator can be used to show when the acid and alkali have completely reacted to produce a salt solution.

salt solutions can be crystallised to produce solid salts.

preparing a insoluble salt. Two soluble metal salts react with each other to form one soluble salt and one insoluble salt.

displacement.

precipitate recovered by filtration

The carbonates of magnesium, copper, zinc, calcium and lithium decompose on heating (thermal decomposition) in a similar way.

Metal carbonates react with acids to produce carbon dioxide, a salt and water.

Limestone, calcium carbonate CaCO3, can be used as a building material. or powered to use to control the acidity of the soil.

Acid + metal oxide --> salt + water

acid + metal hydroxide -> salt + water

Acid + metal carbonate -> salt + water + CO2

Acid + Metal --> salt +hydrogen