Acids, alkalis and salts

• An aqueous solution is formed when a substance dissolves in water. They can be acidic, alkaline or neutral
• Acid + carbonate → salt + water + carbon dioxide
• When a non metal reacts with oxygen it forms an oxide. When these gases dissolve in water they make acids
• When metals burn in air they react with oxygen to make solid oxides, when these dissolve in water they make alkalis
• In HCl blue litmus goes red, red litmus has no change
• In NaCl and H2O blue litmus stays unchanged
• In H2O red litmus is unchanged and in NaCl red litmus goes purple
• In HCl universal indicator and methyl orange go pinkish red
• In NaCl and H2O universal indicator goes light green
• In NaOH universal indicator goes blue/purple
• In NaOH methyl orange goes orange/yellow
• In NaCl and H2O methyl orange is unchanged
• In HCl, NaCl and H2O phenolphthalein is unchanged
• In NaOH phenolphthalein is pinkish purple
• Acids are substances that form hydrogen ions when added to water
• Bases are metal oxides and metal hydroxides
• all alkalis are bases but not all bases are alkalis
• Alkalis are substances that form hydroxide ions when added to water
• When an acid is added to an alkali they react together, this reaction is called neutralisation
• When acids react with metals, bases, metal carbonates, metal hydro carbonates or ammonia, salts are formed
• Indicators are chemicals that change colour in the presence of an acid or an alkali
• An aqueous solution is formed when a substance dissolves in water. They can be acidic, alkaline or neutral
• Bases are substances that react with acids by absorbing hydrogen ions
• Acid + base ➡️ salt + water
• For every increase of 1 on the pH scale, the concentration of H+ ions in an acid decreases by a factor of 10
• To check how much something neutralises an acid measure how much carbon dioxide is given off
• A substance’s solubility is a measure of the maximum mass of a substance can dissolve in a given volume of solvent at a particular temperature
• Substances that are very highly soluble have high solubilitites whilst substances that are insoluble have low solubilities
• What colour is the precipitate lead nitrate?

  white
• Acid + alkali ➡️ salt + water
• Acid + metal ➡️ salt + hydrogen
• The more reactive the metal the faster the reaction will go, the speed of the reaction is indicated by the rate at which the bubbles of hydrogen are given off
• Metal + water ➡️ metal hydroxide + hydrogen
• The amount of energy given out by the reaction increases with the reactivity of the metal
• The reactivity series:

  1. potassium
  2. sodium
  3. lithium
  4. calcium
  5. magnesium
  6. aluminium
  7. zinc
  8. iron
  9. copper
  10. silver
  11. gold
• More reactive metals react more strongly than less reactive metals. This means that a more reactive metal will displace a less reactive metal from its oxide because it will bond more strongly to the oxygen
• If you put a reactive metal into a solution of a less reactive metal salt the reactive metal will replace the less reactive metal in the salt
• Titrations allow you to find out exactly how much acid is needed to neutralise a quantity of alkali
• Soluble:

  • common salts of sodium, potassium and ammonium
  • nitrates
  • common chlorides
  • common Sulfates
  • sodium, potassium and ammonium carbonates and hydroxides
• Insoluble:

  • silver chloride
  • lead chloride
  • lead, barium and calcium Sulfate
  • common carbonates
  • common hydroxides