Intro, Neutralization, Salts


IGCSE Chemistry (C4 Acids and Bases) Note on Intro, Neutralization, Salts, created by ShreyaDas on 27/03/2014.
Note by ShreyaDas, updated more than 1 year ago
Created by ShreyaDas almost 10 years ago

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Properties of Acids:- turns litmus paper red- destroys the chemical properties of bases = neutralizes bases- conducts electricity

Properties of Bases- turns litmus paper blue- destroys the chemical properties of acids = neutralizes acids- conducts electricity

Bases neutralize acids- usually metal oxides, hydroxides, or carbonates- not all are soluble in water- soluble base = alkali

hydroxide = OHcarbonate = CO3nitrate = NO3oxide = O

IndicatorsIndicators are used to find out if a liquid is acidic they change colour when added to acids or alkalis Litmus is a dye that turns red when added to acid and blue when added to alkali Universal indicator (mix of several indicators) pH scale - devised to let chemists measure the strength of an acidic or alkaline solution - measures on a 14 point scale- can change into several colours depending on the pH of the solution - each units represents 10x in acidity- can also be found using a pH meter

Salts can be formed when a base neutralises an acid when sodium hydroxide neutralizes hydrochloric acid = solution of the salt sodium chloride is formed (and water) Acid + reactive metal --> Salt + Hydrogen Acid + Metal Oxide --> Salt + water Acid + metal hydroxide --> salt + water acid + metal carbonate --> salt + water + carbon dioxide acid + excess metal --> salt + water + unreactive metal Acid + Ammonia --> Ammonium salt zinc did not react with any of the acid solutions magnesium reacted most strongly product of: salt + water salt + hydrogen salt + water + carbon dioxide  means that it was acidic

Normal Salts:compound that has been formed when all the hydrogen ions have been replaced by metal ions or by the ammonium ion (NH4)

Soluble Salts:- all nitrates- all common sodium, potassium and ammonium salts- all chlorides except lead, silver and mercury- all sulphates but lead, barium and calcium 

Excess metal or base is added to an acid until all of the acid has reacted -- no more solid will dissolveexcess solid is removed by filtration^suitable for making soluble salts when the solid reactants are insolublefiltering is only suitable for making soluble salts -- if it was insoluble it would get stuck in the filter paper  

1. Metal with a dilute acidMETAL + ACID --> SALT + HYDROGEN GASdo not use this is the metal is very reactive eg sodium or very unreactive eg copper2. Insoluble base (metal oxide) with an acidDo not use this if the base is soluble (an alkali) -- when filtering the excess base it will not get stuck in the filter paper and will not separate from the saltACID + METAL OXIDE --> SALT + WATER3. Insoluble base (metal carbonate) with an acidDo not use if the carbonate is soluble CARBONATE + ACID --> SALT + CARBON DIOXIDE + WATER

Soluble Salts:React an excess of the solid with an acid to make sure that all the acid has been neutralized.Acid + MetalMethod: Measure out some acid into a beaker Add the solid metal in excess into the beaker Filter the mixture to remove the excess metal Heat the filtrate to evaporate some water Leave to cool and crystallize Wash with a little distilled water & pat dry with filter paper

Only suitable for making soluble salts because if insoluble it wouldn't separate from the excess metal and would get stuck in the filter paper

Titrationin other method soluble bases cannot be filtered out Sodium, potassium, calcium react with cold water = alkalisALKALI + ACID --> SALT + WATER

Use: To find the amount of acid needed to neutralize a certain amount of alkali or vice versa.Equipment: Set limit of acid/alkali in a CONICAL FLASK Burette to find the amount to neutralize the acid/alkali Indicator Pipette Method: Fill the burette with acid/alkali and take note of the reading. Read it to the nearest 0.05 cm3 Pipette 25cm3 of the alkali/acid into a conical flask Add a few drops of indicator Add the acid to the alkali swirling the mixture constantly The end point is determined by the colour the indicator reaches. If phenolphthalein than the end point colour will be a light pink. If univeral indicator than the solution colour will be green. If methyl-orange is used than the colour will be salmon pink. Record the reading of the end point on the burette. Repeat without adding the indicator

Pour the neutral solution into an evaporating basin and evaporate about half the waterPour the concentrated solution into a petri dish set aside to cool and crystallize

crystals form because salts are less soluble in colder liquids

Precipitationprecipitate = insoluble solid that forms out of a mixture of solutions

when solutions of two soluble salts are mixed -- two new combinations of ions are possibleif either of these new combinations produce an insoluble salt then a precipitate will formspectator ions are left

Method: Prepared by using a precipitation reaction Two soluble solutions of the insoluble salt are mixed together. One with the cation, one with the anion Stir the mixture until a precipitate forms Filter the mixture to obtain the insoluble salt Rinse with a little bit of distilled water and pat dry with filter paper

Precipitate: insoluble product in a reactionSpectator Ion: ions that don't change their state in a reaction ie. ions that don't reactIonic Equation: equation without spectator ions ie. showing the real reaction

Neutralisationacids and bases = chemical opposites when they react together they destroy each other’s characteristics = neutralisation heat is produced (Exothermic reaction) HCl + NaOH --> NaCl + H2O remove spectator ions = H+OH --> H2O

Phenolphthalein Indicatoracid: colorlessbase: pink

sodium c

All soluble:sodium compoundsnitratesammonium saltspotassium compounds

Properties and Indicators

Salts and Neutralisation

Making a Soluble Salt

Making a Soluble Salt II (soluble reactants)

Making Insoluble Salts

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