Acids, Alkalis, And Salts (Y11)

Red in acid Blue in alkali

Clear in acid Pink in alkali

Pink/red in acid Yellow in alkali

• acids neutralises bases • they dissolve in water • they release H+ ions

• strong acids disassociate their H+ ions fully • weak acids disassociate their H+ ions partially • pH measures the number of H+ ions lost

• dissolve in water * release hydroxide(OH-) ions

• don’t dissolve in water • neutralise acids E.g. Copper or iron oxide, zinc carbonate

Add excess base: (e.g. Making copper sulphate) • Add excess base to the acid until no more dissolves (warm acid if necessary) • Filter off excess base • Obtain dry salt from the solution

Titration: (e.g. Hydrochloride acid and sodium hydroxide) • Measure out the alkali using a pipette, and pour into conical flask • Add acid via a Burnett to alkali, slowly, occasionally mixing, until indicator is neutral • Add the same volume of acid to the same amount of alkali WITHOUT indicator • Obtain dry salt from solution

Precipitation: (e.g. Making lead iodide) 1. Make two solutions each containing an ion of the salt you want to make (these must be soluble) 2. Mix the solutions 3. Filter off the precipitate- the insoluble salt 4. Wash the precipitate with distilled water to remove any other salt solutions 5. Dry on filter paper or warm gauze Example: sodium iodide + lead nitrate ➯ lead iodide + sodium nitrate Colourless solution + colourless solution ➯ yellow precipitate + colourless solution

All nitrates All chlorides except silver and lead All sulfates except barium lead and calcium Potassium, sodium and ammonium carbonates

Silver chloride, lead chloride Barium sulphate, lead sulphate, calcium sulphate All carbonates except potassium, sodium, and ammonium

1. Is the salt soluble? No: precipitation Yes: 2:Is the base soluble? (I.e. Is it a hydroxide) No: add excess base Yes: titration

• mix acid and base • add excess base until it no more dissolves • filter • heat to get rid of some water • leave to crystallise • wash w distilled water to get rid of any remaining acid/alkali

• measure out alkali using pipette and pour into conical flask • add acid via a burette slowly, mixing occasionally, until indicator turns neutral • repeat but w/o indicator • heat solution to get rid of most of water • filter to remove water • allow to crystallise

• make two soluble solutions each containing an ion of the salt you want • mix • filter off the precipitate- the insoluble salt • wash w distilled water to get rid of any other salt solutions • dry on filter paper/warm gauze

Concentration (moldm-3) = moles / volume

• balance eq • write in what we know and what we must find out • work out mols of known • use ole ratios to find mols of unknown • using vol of unknown find conc of unknown