C4 - Acids and Alkalis

• What are Ores?

  Ores are naturally occurring rocks which contain metals - These are oxidised metals
• What is the equation of metal and oxygen reacting?

  Metal + Oxygen -> Metal Oxide
• How do we extract metals from their ores?

  Via reduction reaction
• What is the Mnemonic for the reactivity series?

  Please - Potassium

  Send - Sodium

  Lions - Lithium

  Cats - Calcium

  Monkeys - Magnesium

  And - Aluminium

  Cute - Carbon

  Zebras - Zinc

  Into - Iron

  Hot - Hydrogen

  Countries - Copper

  Signed - Silver

  Gordan - Gold
• What is the equation for a Metal and Water reacting?

  Metal + Water -> Metal Hydroxide + Hydrogen
• What is the equation for Metal and an Acid reacting?

  Metal + Acid -> Salt + Hydrogen
• What is a displacement reaction?

  A chemical reaction when a more reactive metal displaces a less reactive metal from a compound
• What is the equation for neutralisation?

  Acid + Base -> Salt + Water
• What is the equation for an Acid reacting Metal Oxide?

  Acid + Metal Oxide -> Salt + Water
• What is the equation for an Acid reacting with Metal Hydroxide?

  Acid + Metal Hydroxide -> Salt + Water
• What is the equation for an Acid reacting with Metal Carbonate?

  Acid + Metal Carbonate -> Salt + Water + Carbon Dioxide
• What do Metal Oxides, Metal Hydroxides and Metal Carbonates have in common?

  They're BASES
• For Metals, what is their reactivity determined by?

  How easily they lose electrons - forming positive ions.
• The higher a metal is up the reactivity series...

  The more easily they form positive ions
• How can we tell how reactive a metal is?

  • The rate at which the bubbles of hydrogen gas are given off
  • The rate of the reaction
• What is the mnemonic for oxidation and reduction?

  O - Oxidation

  I - Is

  L - Loss of electrons

  R - Reduction

  I - Is

  G - Gain of electrons
• Metals higher than carbon in the reactivity series have to extracted by..

  Electrolysis
• Metals below carbon in the reactivity series can be extracted by..

  Reduction using carbon
• What is a redox reaction?

  When a reduction and oxidation reaction occurs at the same time
• When is Electrolysis used?

  Metals that are more reactive than carbon
• Can Ionic solids be electrolysed?

  No they can't, this is because ions are in a fixed position and can't move - instead molten ionic compounds can be electrolysed OR ionic solids dissolved in water because the ions can move freely and conduct electricity
• What is aluminium oxide mixed with, and why?

  Cryolite, to lower the melting point
• Electrolysis of Aluminium Oxide Explained:

  1. The Al3+ ions are attracted to the cathode, they GAIN 3 electrons. HALF EQUATION: Al3+ + 3e- -> Al
  2. The O2- ions are attracted to the anode, they LOSE 2 electrons. HALF EQUATION: O2- -> O + 2e- OR O2- - 2e- -> O
• Why does O2- LOSE electrons, rather than gain?

  O2- Is a negatively charged ion, therefore it gained electrons. To return back to an atom it must LOSE them 2 electrons.
• Why does Al+3 GAIN electrons, rather than lose?

  Al+3 is a positively charged ion, therefore it lost 3 electrons. To return back to an atom it must GAIN them 3 electrons.
• Strong acids completely ionise in water, weak acids partially ionise in water
• In aqueous solutions, acids produce...

  • Hydrogen Ions (H+)
• What is a base?

  • Bases are chemicals which can NEUTRALISE acids, producing a salt and water
• In aqueous solutions, alkali's produce...

  • Hydroxide Ions (OH-)
• What are alkali's?

  • Bases which are soluble in water are known as alkali's
  • They have a pH between 8-14
  • In aqueous solutions they produce Hydroxide Ions
• pH Scale

  • 0-6 = Acid
  • 7 = Neutral
  • 8-14 = Alkali
• What can be used to identify whether a solution is either an acid, alkali or neutral?

  • pH probe
  • Universal Indicator
• State the colours of acids, alkali's and neutral substances (UNIVERSAL INDICATOR)

  • Acid = Red
  • Alkali = Purple
  • Neutral = Green
• What is a strong acid?

  • Strong acids FULLY IONISE in aqueous solutions (every molecule splits)
  • E.g. Hydrochloric acid, Nitric acid
• What is a weak acid?

  • Weak acids PARTIALLY IONISE in aqueous solutions
  • E.g. Carbonic acid, Ethanoic acid, Citric acid
• What is the link between the pH scale and how strong an acid is?

  • Strong acids will have a LOWER pH -> This is because strong acids FULLY IONISE producing a greater concentration of Hydrogen Ions (H+)
• As the pH decreases by one unit...


  • The concentration of Hydrogen Ions (H+) increases by 10 times
• How can we predict what is produced at the CATHODE in AQUEOUS SOLUTIONS?

  • The ion of the least reactive element is discharged
• How can we predict what is produced at the ANODE in AQUEOUS SOLUTIONS?

  • If a HALIDE ION is present, the HALOGEN is produced
  • If a HALIDE ION isn't present, ALWAYS OXYGEN is produced (from the OH- ions)
• What is meant by concentration?

  • The amount of acid molecules in a given volume of solution