Acids, Alkalis, Salts Flashcards
Colours of litmus
Red in acid
Blue in alkali
Colours of phenolphthalein
Colourless in acid
Pink/purple in alkali
Colours of methyl orange
Red in acid
Yellow in alkali
What is universal indicatior
• mixture of indicators • shows pH • 0-14 • 1- many H+ ions • 14- very few H+ Green in neutral Red in acid Blue in alkali
What are acids
Substances which dissociate in water and release hydrogen ions, H+ e.g HCl
Define dissociation
When substance ‘split up’ in water and form ions
What are alkalis
Substances which dissolve in water to release hydroxide irons, OH- e.g NaOH
What is neutralisation
A reaction between an acid and an alkali, it involves hydrogen ions being changed into water molecules by reacting with hydroxide ions of the alkali (H + OH -> H2O
Reactions to make salts:
Acid + metal
Salt + hydrogen
E.g 2HCl + Mg -> MgCl2 + H2
Reactions to make salts:
Acid + metal oxide
Salt + water
E.g 2HCl + MgO -> MgCl2 + H2O
Reactions to make salts:
Acid + metal hydroxide (alkali)
Salt + water
E.g HCl + NaOH -> NaCl + H2O
Reactions to make salts:
Acid + metal carbonate
Salt + water + carbon dioxide
E.g 2HCl + CaCO3 -> CaCl2 + H2O + CO2
Dissociation of hydrogen chloride
HCl (g) + H2O (L) -> H3O (aq) + Cl (aq)
Simply : HCl (aq) -> H (aq) + Cl (aq)
Why is there no dissociation when hydrogen chloride is added to methylbenzene
Because hydrogen chloride doesn’t behave like an acid, it doesn’t conduct electricity nor change colour of indicators
Titration
- uses neutralisation
- phenolphthalein indicator is added to the beaker
- you record how much acid is used to make the alkali go purple (Neutralisation, when the indicator changes colour)
- acid is added to the titration funnel
- The alkali is in the beaker
