Acids, Bases and salts

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• Acids Bases and Salts

• Acids identified by the presence H+ ions

• Metal carbonates

• BasesIdentified 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 -> chlorideSulphuric 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 dm3e.g.  25cm3 of HCL = 25/1000 = 0.025 dm3step 2 - Determine the number of moles.Moles = conc. x volumestep 3 - work out the number of moles of acid using the balanced equation.step 4 - conc = number of moles / volumeanswer = 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 + wateracid + metal hydroxide -> salt + waterAcid + metal carbonate -> salt + water + CO2Acid + Metal --> salt +hydrogen