2.1.4 acids

Releases H+ ions in aqueous solutions Proton donor Most common: HCl, H2SO4, HNO3

Neutralise acids Proton acceptor Most common: metal oxides, metal hydroxides, ammonia

Soluble base that releases OH- ions in aqueous solution Most common: NaOH, KOH, NH3

Completely dissociate when dissolved in water

Slightly dissociate when dissolved in water, giving an equilibrium mixture

Formed from neutralisation reactions Formed when H+ ion of an acid is replaced by a metal ion or an ammonium ion

Acid + base > salt + water Acid + carbonate > salt + water + CO2

Salt + water

Salt + water + CO2 • effervescence due to CO2 gas evolved and solid carbonate dissolves

Pipette 25cm3 of alkali into conical flask Add acid solution from burette Add a few drops of indicator and refer to colour change White tile underneath to help observe colour change Add acid to alkali whilst swirling mixture and add acid dropwise at end point Note burette reading before and after Repeat until at least 2 concordat titres

Pink (alkali) to colourless (acid) Use if NaOH is used

Yellow (alkali) to red (acid), end point orange Use if HCl is used

Acids and alkalis are corrosive Wear eye protection and gloves if spilled immediately wash affected parts

Should be clearly recorded in a table Result should be recorded in full Record titre volumes to 2dp

sodium hydrogen carbonate (NaHCO3) and CaCO3 good for neutralising excess acid in the stomach or acid spills as not corrosive

% uncertainty = (uncertainty / measurement made on apparatus) x 100

% uncertainty = (uncertainty / measurement made on apparatus) x 100

Replacing measuring cylinders with burettes or pipettes which have lower apparatus uncertainty Titrate a larger volume - increase volume and concentration of substance in conical flask

Decrease sensitivity uncertainty by using apparatus with greater resolution (finer scale divisions) or increase size of measurement made

Difference between values / original x 100