-
Aqueous Solutions (aq)
-
substance disolved in water
- alkaline
- acid
- neutral
-
indicators
- test for acidity / alkalinity
- liquid
- paper
- different colours / different solutions
-
litmus
-
acid
- red
-
neutral
- purple
-
alkaline
- blue
-
universal indicator
- shows strength of acid / alkalis
- more colours
-
pH scale
- 1 to 6
- acid
- 7
- neutral
- 8 to 14
- alkaline
-
Phenolphthalein indicator
- colourless in acid
- pink in alkaline
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Methyl Orange Indicator
- pink in acid
- yellow in alkaline
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Acids
-
contain replaceable hydrogen atoms
- chemcial reactions
- metal atom replacement
-
salt compound formed
- (see mind map on salts)
-
only in aqueous solution
- form H+ ions
- HCl (aq) ---> H+ (aq) + Cl- (aq)
-
basicity
-
number of H+ that can be replaced
-
hydrochloric acid : HCl
- monobasic (one H+)
-
nitric acid : HNO3
- monobasic (one H+)
-
sulphuric acid : H2SO4
- dibasic (two H+)
-
phosphoric acid : H3PO4
- tribasic (three H+)
-
Types
-
strong acid
- produce all hydrogen ions available
- HCl, HNO3, H2SO4, H3PO4
- use one way arrow symbol --->
-
weak acid
- partially dissociate
- not release all hydrogen ions
- molecules in equillibrium with ions
-
use double arrow symbol
-
ethanoic acid
- vinegar
- CH3COOH (aq) <--> CH3COO- (aq) + H+ (aq)
-
Bases / Alkalis
-
Base
-
hydroxides of metals
-
formed when oxide dissolves in water
- alkali
-
oxides of metals
- 4Na (s) + O2 (g) ---> 2Na2O (s)
- sodium + oxygen ---> sodium oxide
-
dissolve a base into water
-
alkali
- Arrhenius : substances that dissolve
in water to form hydroxide ions OH-
- NaOH(aq) ---> Na+ (aq) + OH- (aq)
- pH 8 - 14
-
strong alkalis
-
fully dissociate
- release all hydroxide ions
-
sodium hydroxide
- sodium oxide + water ---> sodium hydroxide
- Na2O (s) + H2O (l) ---> 2NaOH (aq)
-
potassium hydroxide
- KOH (aq) ---> K+ (aq) + OH- (aq)
- use one way arrow symbol --->
-
weak base (weak alkali)
-
ammonia solution
- ammonium hydroxide solution
- NH4OH (aq)
- NH3 (g) + H2) (l) <---> NH4+ (aq) + OH- (aq)
- NH4OH(aq) <---> NH4+ (aq) + OH - (aq)
- partial dissociation