Acids and Alkalis Flashcards
Define acid
A substance that produces H+ ions in an aqueous solution
A proton donor
Define base
A substance that neutralises acids
A proton acceptor
Define alkali
A water soluble base that produces OH- ions in an aqueous solution
Acid + metal =
Salt + hydrogen
Acid + metal (hydr)oxide=
Salt + water
Acid + metal carbonate =
Salt + water + carbon dioxide
Describe how to do a titration (8 steps)
1) use pipette to measure alkali into a conical flask
2) add phenolphthalein (will go pink)
3) fill burette with acid
4) add acid to conical flask until one drop turns the solution colourless
5) record burette volume (titre) and repeat until you get concordant results (within 0.1cm^3)
6) repeat without indicator
7) heat to crystallisation point then filter and wash with distilled water
8) leave in drying oven/ between filter paper for the water to evaporate leaving pure salt
Describe how to make salt using the excess solid method
1) Add insoluble solid to hot acid and stir
2) add the solid to excess
3) filter
4) heat gently to evaporate some of the water
5) leave solution to cool and salt to crystallise
6) filter off salt, wash with distilled water and leave to dry
Describe how to make salts using the precipitation method
1) mix 2 solutions in a beaker
2) filter out the insoluble salt
3) wash with distilled water and dry in a drying oven
What is the ionic equation for neutralisation ?
H^+ (aq) + OH^- => H2O (l)
Define strength of an acid
To do with how many H+s there are.
Not all acids completely dissociate: the more dissociation the stronger the acid because there is more spare H+
Define concentration
Amount of acid/alkali in a set volume of water
More acid/alkali = more concentrated
Units = mol/dm^3
What salts are always soluble?
Nitrates
Sodium, potassium & ammonium
Which halides aren’t soluble?
Silver or lead halides
Which sulphates aren’t soluble?
Lead, barium and calcium sulphates
