Acids and Bases

• indicators


  Chemicals that change colour in the presence of an acid or alkali
• Acids


  • pH below 7 and turn universal indicator yellow, orange or red
  • Turn litmus red
  • Solutions contain hydrogen ions (H+)
• Acids


  • Hydrochloric acid (HCl) - strong acid
  • Ethanoic acid (vinegar) - weak acid
  • Sulfuric acid (H2SO4)
  • Nitric acid (HNO3)
• Alkalis


  • pH above 7 and turn universal indicator blue or purple
  • Turn litmus blue
  • Neutralise acids
  • Solutions contain hydroxide ions (OH-)
• Alkalis


  • Sodium hydroxide (NaOH) - strong alkali
  • Potassium hydroxide (KOH)
  • Calcium hydroxide (Ca(OH)2)
  • Ammonia (NH3) - weak alkali
• Bases


  Substances that react with acids by absorbing hydroxide ions
• Bases


  • Oxides
  • Hydroxides
  • Carbonates of metals
  • Ammonia (which doesn't contain a metal)
• Soluble


  Substances that dissolve in a solvent
• Soluble substances

  • Ammonium salts
  • Potassium salts
  • Sodium salts
  • Nitrates
  • Chlorides (except lead and silver)
  • Sulfates (except barium, calcium and lead)
• Insoluble substances


  • Carbonates (except potassium, sodium and ammonium)
• Relative formula mass

  The mass of one mole of a substance
• Acid-alkali titration


  Accurately adding an acid to an alkali to produce a salt and water
• Universal Indicator

  • Changes alkalis to blue/purple

  • Changes acids to red/orange

  • Neutral would be green (water)
• Methyl orange

  • Shows red to yellow (pH 4.4 to 6.2)
• Phenolphthalein

  • Shows colourless to pink (pH 8-10)
• Litmus paper

  • Acid: Blue litmus turns red (pH 5)
  • Base; Red litmus turns blue (pH 8)
• Acids chemical formula:

  Acid + water = X + Hydrogen+
• Bases chemical formula:

  Base + water = X + Hydroxide-
• Acids and metals

  Metal + Acid = Salt + Hydrogen

  Mg + 2HCl = MgCl2 +H2
• Acids and Bases

  Acids react with bases:

  • Metal oxides
  • Metal hydroxides

  Forming Water and Salt
• Neutralisation reaction

  Base + acid = Water + Salt

  CaO + H2SO4 = H2O + CaSO4
• Neutralisation reaction

  Carbonate + acid = Water + Carbon dioxide + Salt

  ZnCO3 + HNO3 = H2O + CO2 + Zn(NO3)2
• Acids and carbonates

  Metal carbonate + acid = Water + Carbon dioxide + Salt

  NaCO3 + H2SO4 = H2O + CO2 + NaSO4
• Hydrochloric acid = HCl (aq)

  Salt: NaCl - Chlorides
• Nitric acid = HNO3 (aq)

  Salt: KNO3 - Nitrates
• Sulfuric acid = H2SO4 (aq)

  Salt: CuSO4 - Sulfates
• Ethanoic acid = CH3COOH

  Salt: CH3COONa - Ethanoates
• Phosphoric acid = H3PO4

  Salt: K3PO4 - Phosphates
• Sodium hydroxide + hydrochloride acid practical

  • Mixing them produces a colourless solution
  • When using the thermometer, the temperature rises several degrees, showing there was been a chemical change
  • NaOH(aq) + HCl(aq) = NaCl(aq) + H2O
• Neutralisation reactions for an acid reacing with an alkali involve hydroxide ions from the alkali reacting with H+ ions from the acid to form water

  OH-(aq) + H+(aq) = H2O(l)
• Reactions with zinc and acids

  Slower reactions as zinc is lower down in the reactivity series

  • Zn(s) + H2SO4(aq) = ZnSO4(aq) + H2(g)
  • Zn(s)+2HCl(aq) = ZnCl2(aq) + H2(g)
• mols = mass(g) : molar mass(g/mol)
• mass = molar mass x mols