Acids And Alkalis Flashcards
phenolphthalein colour changes
Turns alkaline pink
Colourless in acidic or neutral
Dissociation of an acid of alkali is…
Percentage of molecules that have become ions in the solution
e.g OH-, H+
Concentration of an acid or alkali is…
How many molecules of the acid or alkali are in the solution
Rules of solubility
ALL Sodium, ammonium, potassium salts = soluble
All nitrates = soluble
Common chlorides = soluble (except lead & silver)
Common sulfate= soluble (except lead, barium & calcium)
Carbonate and hydroxides= insoluble (except sodium, ammonium & potassium)
How to make an insoluble salt
-Precipitation reaction
-Between two soluble salts
Method
• add each salt to water in different test tubes and dissolve them by shaking the tubes
•add to same beaker
•Shake thoroughly and salt will fully precipitate
•Filter out any soluble salt and scrap precipitate onto a surface to dry
How to make soluble salts
Using an acid and insoluble base
- add acid to insoluble base forming a soluble salt and water
- Filter out all the excess insoluble base so just soluble salt and water left
- Heat gently to evaporate most of the water
- Leave to cool and crystallise
- filter off salt and let it dry
(heat acid at beginning to speed up reaction)
How to make soluble salt
Using acid and alkali neutralisation reaction
Titration
•Measure certain amount of acid into a conical flask using a pipette
•Add 2 drops of indicator (methyl orange or phenolphthalein)
•Using a biurette, slowly add alkali into flask until indicator changes colour
•Carry out experiment again with exact same volume of acid and alkali but no indicator
•Solution remains only salt and water
•Evaporate off water and leave the solution to cool and crystallise
•filter off salt and let it dry
methyl orange colour change
acid turns red
Neutral and alkali turns yellow
To make a Soluble Salt =
ACID + insoluble base
ACID + alkali
To make an insoluble salt
SOLUBLE SALT + SOLUBLE SALT
