Acids, Bases and Salts Flashcards
Definition of an acid
An acid releases H+ ions in aqueous solution. An acid is a proton donor.
Show dissociation of HCl and H2CO3
HCl (aq) –> H+ (aq) + Cl- (aq)
H2CO3 (aq) –> 2H+ (aq) + CO3 2- (aq)
Define a stong acid
A strong acid is fully dissociated in solution
It is not a reversible reaction
Define a weak acid
A weak acid is partially dissociated in solution.
Many are carboxylic or organic acid.
It is a reversible reaction
Show dissociation of CH3COOH
CH3COOH (aq) –> CH3COO- (aq) + H+ (aq)
reversible reaction
Define a base
Bases are proton acceptors
What are the different types of bases
Metal hydroxides
Metal oxides
Ammonia and organic amino compounds
Example of reaction of bases with acids:
NaOH +HCl
MgO + HCl
NH3 + H+
NaOH +HCl –> NaCl + H2O
MgO +2HCl –> MgCl2 + H2O
NH3 (aq) + H+ (aq)–> NH4+ (aq)
Neutralisation reaction
H+ + OH- –> H2O
Define an alkali
An alkali is a water soluble base that releases OH- ions in water e.g. NaOH, KOH, NH3
What happens when acid dissolves in water
The acid dissociates and the hydrogen ion is accepted by a water molecule so the water molecule is acting as a base.
H+ + H2O –> H3O+
(hydronium ion)
Water soluble metal oxide with water
water soluble metal oxide react with water to form aqueous hydroxides
If added to aqueous acid the hydroxide forms can react further to form water.
Water soluble metal hydroxide with water
Water soluble metal hydroxides dissolve and release hydrated OH- ions in water
NaOH (s) + aqua–> Na+ (aq) + OH- (aq)
Water is aqua because it is acting as a solvent and is not reacting chemically.
Define a salt
Salts are ionic compounds formed when H+ ions are replaced by metal ions or ammonium ions
Reactions of acids
Acid + Metal hydroxide –> Salt + Water
Acid + Metal oxide –> Salt + Water
Acid + Metal carbonate –> salt + CO2 + Water
Acid + Reactive metal –> salt + hydrogen
What happens when ionic compounds are added to water e.g NaCl
The ions leave the solid lattice and become separate hydrated ions . The polar water molecules surround the ions in the lattice and separate them form their compound. the separate ions are completely independent of each other so can react without affecting the other.
Ions that form soluble compounds
- Group 1 ions
- Ammonium
- Nitrate
- Hydrogen carbonate
- Halides- except when with Ag+, Pb2 + or Hg2+
- Sulfate- except when with Ag+, Pb2 +, Ca2+, Sr2+, or Ba2+
Ions that form insoluble compounds
- Oxide- except with group 1 melals , Ca2+, Ba2+
- Carbonate- except with group 1 ions or ammonium
- Phosphate- except with group 1 ions or ammonium
- Hydroxide- except with group 1 ions or ammonium, Ca2+, Mg 2+, Sr 2+, Ba2+
- Sulfide- except with group 1 ions or ammonium
- Chromate- except with group 1 ions or ammonium, Ca2 +, Mg 2+
Test for Halide ions
- Add Ag+ ions
- Then dilute ammonia solution
- Then concentrated ammonia
Results
Chlorine- White precipitate forms, dissolves in dilute and concentrated ammonia
Bromine- Cream precipitate forms, only dissolves in concentrated ammonia.
Iodine- Yellow precipitate forms, doesn’t dissolve in either ammonia solutions.
Test for carbonate ion
Add nitric acid
Results
Should see effervescence and gas produced should turn lime water cloudy.- CO2
Test for sulfate ions
Add Ba 2+ ions as barium chloride or nitrate
Results
A white precipitate should form
Test for ammonium
Add NaOH and warm it up
Results
Turn damp red litmus paper blue
What are spectator ions
Ions that don’t undergo changes in a reaction and stay in solutions. Remove these in ionic equations
Rules for ionic equations
- Remove spectator ions
- Don’t separate solids into ions
- Don’t separate covalent compounds into ions
- The atoms and the charge must be balanced
