Topic 4 - Extracting Metals and Equilibria

• pH scale


  • Shows how acidic or alkaline a substance is
  • 0-6 is acidic
  • 7 is neutral
  • 8-14 is alkaline
• Alkalis


  • Soluble bases
  • Bases are chemicals that can neutralize acids
• Dissociation


  1. Acids split up into hydrogen ions (H+)

  2. Alkalis split up into hydroxide ions (OH-)
• Strong vs Weak acids/alkalis

  • Strong completely dissociate into ions
  • Weak only partially dissociate
• Concentrated vs Dilute


  • Concentrated has a lot of the substance
  • Dilute has only a small amount of the substance
• Common acids


  • Hydrochloric acid (HCl)
  • Nitric acid (HNO3)
  • Sulfuric acid (H2SO4)
• Common bases/alkalis


  • Sodium hydroxide (NaOH)
  • Potassium hydroxide (KOH)
  • Calcium hydroxide (Ca(OH)2)
• Indicators


  • Used to test if a substance is an acid or alkali
  • Methyl orange, phenolphthalein, red/blue litmus paper, universal indicator
• Testing for gases


  1. Hydrogen - squeaky pop with lit splint

  2. Carbon dioxide - turns limewater cloudy

  3. Oxygen - relights glowing splint
• Neutralization


  1. Acid and base react to form a salt and water

  2. Resulting solution has pH 7 (neutral)
• Acid reactions


  • Acid + metal oxide/hydroxide = salt + water
  • Acid + metal = salt + hydrogen
  • Acid + metal carbonate = salt + water + carbon dioxide
• Salts


  • Products formed when acids and bases react
  • Can be soluble or insoluble
• Making copper sulfate


  1. React copper oxide with sulfuric acid

  2. Add excess copper oxide

  3. Filter off unreacted copper oxide

  4. Crystallize to get pure copper sulfate
• Titration


  • Used to control the exact amount of reactants added
  • Uses a burette to gradually add drops of one reactant to the other
• Electrolysis


  • Using electricity to split up ionic compounds
  • Positive ions move to cathode, negative ions move to anode
• Oxidation and Reduction in electrolysis

  1. Oxidation is loss of electrons at anode

  2. Reduction is gain of electrons at cathode
• Electrolysis of dissolved ionic compounds

  1. Less reactive ion is given off at electrodes

  2. Hydrogen given off at cathode, chlorine given off at anode
• Half equations can be used to describe the reactions at each electrode during electrolysis
• Reactivity series of metals

  Orders metals from the most reactive to the least reactive
• Metals in reactivity series

  • Potassium
  • Sodium
  • Lithium
  • Calcium
  • Iron
  • Silver
  • Gold
• Oxidation


  Gain of electrons or gain of oxygen
• Reduction

  Loss of electrons or loss of oxygen
• Metals above hydrogen in reactivity series

  React with dilute acids
• Top 4 metals in reactivity series

  React with cold water
• Reaction of metal with water

  Metal hydroxide + hydrogen
• Displacement reaction

  Reaction where a more reactive metal replaces a less reactive metal in a compound
• Displacement reactions are redox reactions with oxidation and reduction happening
• Extraction methods for metals

  • Electrolysis for metals above carbon
  • Carbon reduction for metals above silver
  • Natural state for silver and gold
• Extraction of iron using carbon

  Iron oxide + carbon -> carbon dioxide + iron
• Low grade ores

  Ores with a lot of rock and not much metal to make a profit
• Methods for extracting metals from low grade ores

  • Bio leaching using bacteria
  • Phytoextraction using plants
• Reversible reaction


  Reaction that can go forwards and backwards
• Dynamic equilibrium

  Forward and backward reactions happening at the same rate
• Dynamic equilibrium can only occur in a closed system
• Position of equilibrium

  The side of the reaction with more material
• Factors that affect position of equilibrium

  • Temperature
  • Pressure
  • Concentration
• Exothermic reaction

  Reaction that releases heat
• Endothermic reaction


  Reaction that absorbs heat
• The Haber process for producing ammonia uses an iron catalyst
• Decreasing temperature in Haber process

  Increases amount of ammonia produced but slows the reaction