C5 - Separate Chemistry 1

• TITRATION (NaOH and HCl)

  finding exact volumes of acid/alkali used to neutralise

  1. Add HCl to burette to 0ml line
  2. Add 25cm3 NaOH to conical flask (using pipette)
  3. Add in phenolphthalein
  4. Slowly add HCl until colourless (neutral)
  5. Repeat for concordant titres
• Percentage yield

  compares actual yield with theoretical yield

  • (actual yield ÷ theoretical yield) x 100
• Actual yield

  • actual amount of product formed in a chemical reaction
• Theoretical yield

  • maximum calculated mass that is formed from a given amount of reactions
• Reasons yield is less that expected:

  • reaction is incomplete
  • product is lost
  • unwanted side reactions take place
• Atom economy

  
  

  showing how efficiently a particular reaction makes use of the atoms in the reaction

  • (relative formula mass of useful product ÷ sum of RAM's of all reactants) x 100
• Fertilisers (N, P and K)


  Replace the mineral ions needed by plants and promote plant growth

  • Nitrogen, phosphorous and potassium
• Ammonium nitrate

  Made in a neutralisation reaction

  • ammonia solution with dilute nitric acid
• Nitric acid

  Made in an oxidation reaction

  • from ammonia with oxygen and water in several reactions
• Properties of transition metals

  
  

  • form coloured compounds
  • metals are strong and hard
  • useful as catalysts (iron in Haber process)
  • high density
  • not very reactive
  • form different ions (Fe2+, Fe3+)
• Properties of transition metals

  Good conductors of electricity

  • delocalised electrons that can move and carry charge

  Good conductors of heat

  • closely packed inside structure

  Ductile and malleable

  • layers can slide over each other

  High melting point

  • strong metallic bonds
• Metallic bonding

  A strong electrostatic force of attraction between a lattice of positive metal ions in a sea of delocalised electrons.
• Structure of metals

  Lattice of metal atoms in a cloud of delocalised outer shell electrons
• Alloy


  A mixture of a metal element with one or more other elements
• Alloys are harder/stronger than pure metals 


  Different sized atoms (disrupts the lattice)

  • harder for layers to slide
• Oxidation


  Gain of oxygen/loss of electrons
• Corrosion

  the destructive of materials (metals) by reaction with water and/or oxygen
• Corrosion


  1. Metal starts to oxidise on surface
  2. As the metal continues to oxidise, it will weaken over time
• Corrosion forms metal oxides
• Rusting


  Corrosion of iron and steel
• Rusting forms iron oxide
• Using physical barriers to prevent corrosion/rusting


  Paint, oil and plastic/metal coating

  • prevents water and oxygen getting to metal
• Using electroplating to prevent corrosion/rusting


  Cathode = metal that will be protected

  Anode = unreactive metal

  Electrolyte = ionic substance of unreactive metal

  • Ions move from anode to cathode to coat other metal
• Sacrificial protection


  Wrap metal you want to protect in a more reactive metal

  That will oxidise instead of main metal

  • magnesium on railway lines
  • zinc/magnesium on ships
• Uses of electroplating


  Coating cutlery, cooking utensils and jewellery to make them shiny and attractive
• Electroplating

  Redox reaction

  • both oxidation and reduction happen

  oxidation = anode

  reduction = cathode
• Alloys help to...

  • prevent rusting, make the metal stronger
• Properties of gold


  • Good conductors (not as good as copper)
  • Doesn't corrode
  • Expensive
• Properties of jewellery gold (gold and copper alloy)


  • Copper is added ---> jewellery gold
  • Shinier, attractive, stronger
• Properties of copper


  Good conductor

  Cheaper

  Ductile

  • used in electrical circuits

  Malleable

  • pipes
• Properties of brass


  • Copper and zinc alloy
  • Makes it stronger
• Properties of aluminium


  Layer of aluminium oxide on top

  • stops rest of metal corroding
  • used for foil

  Good conductor

  • not as good as copper
  • used for overhead cables

  Less dense than other metals

  Cheaper
• Properties of magnalium alloy


  Magnesium and aluminium metal

  Stronger but still low density

  • used for aircraft parts

  Good resistance to corrosion
• Conditions of the Haber process are called compromise conditions
• Haber Process = N2 + 3H2 ⇌ 2NH3
• Fuel cell


  Device that produces a voltage continuously when supplied with a fuel and oxygen
• Fuel cells


  • Have different strengths and weaknesses, depending on the intended use
  • Used in spacecraft and vehicles
• Fuel cells in spacecraft

  • Have no moving parts to maintain
  • Small for the amount of electricity they produce
  • Produce useful water
• Hydrogen-oxygen fuel cells in spacecraft

  Must be supplied with hydrogen and oxygen
• Spacecraft in orbit


  Have solar cells that convert light into electricity, allowing the hydrogen and oxygen to be replaced by electrolysis of water