CHEMISTRY UNIT 7 - ACIDS 
Practicals
Preparation of crystals of a soluble salt from an insoluble base or carbonate
Titration of a strong acid against a strong base using an indicator
Basics of pH
Acids
Reactions of Acids
Neutral is pH 7 = water
Indicator is a dye that changes colour due to pH
Higher pH more alkaline (8 -14)
Universal indicator is a wide range indicator using mixture of dyes gradually changing colour over board range of pH
Lower pH more acidic (0-6)
pH scale measures how acidic/alkaline solution is
pH probe attached to pH meter can be used to measure pH electronically 
Bases
Insoluble Bases (Neutralisation)
Alkalis (Neutralisation)
Metals
Carbonates
Acid + metal --> salt + hydrogen
Acids will only react with metals if metal is more reactive than hydrogen
If metal too reactive the reaction becomes too dangerous (potassium)
Acid + base --> salt + water
Insoluble base (copper oxide or magnesium oxide) reacts with an acid
Strong/weak acids
Strong acids
Acid = a substance that donates protons in a solution to form hydrogen ions (H+ ions )
Base = any substance that will react with an acid to neutralise acid & form a salt
Alkali
Alkali = a base that dissolves in water to form solution with pH greater that 7, alkalis form hydroxide ions(OH- ions) in water
Acid + alkali --> salt + water
Acid + metal carbonate --> salt + water + carbon dioxide
Weak acids do not fully ionise and are reversible
Concentration = total number of dissolved acid molecules not ionised molecules (how watered down acid is, not how strong)
Strength = what proportion of acid's molecules ionise in water
Ionise completely in water e.g.. sulphuric & nitric
Test to identify CO2 gas
Bubble the test gas through limewater - calcium hydroxide solution. Carbon dioxide turns limewater cloudy white.
Test to identify Carbonate ions using dilute acid
Acid is added to the test compound. If carbonate ions are present then CO2 gas bubbles off. If this is passed through limewater it turns the limewater from clear to cloudy.
Aqueous Neutralisation reactions can be generalised to hydrogen ions reacting with hydroxide ions to form water
H+ + OH- ---> H2O
Hydrogen ion concentration
Concentration = amount of substance (g) ÷ volume of solution (dm3)
Metal oxides & Metal Hydroxides
As hydrogen ion concentration increases by factor of 10, the pH value decreases by 1