Chem Paper 1

• Metal Carbonate + acid → metal salt + carbon dioxide + water
• metal + water → metal hydroxide + hydrogen
• acid + metal hydroxide → salt + water
• Structure of the atom

  Radius of an atom = 1x10^-10 metres = 0.1nm

  Nucleus = 1/10000 size of atom
• History of the Atom

  • Plum Pudding model - JJ Thompson - ball of positive charge with electrons stuck in
  • Nuclear - Ernest Rutherford - Gold leaf experiment, some alpha particles deflected backwards - added nucleus, rest of atom mostly empty space
  • Bohr's Nuclear - Niels Bohr - shells of electrons, not a cloud

  Order:

  • electron
  • proton
  • neutron
• Alkali Metals - Group 1


  Going down the group:

  • reactivity increases
  • Melting/boiling point decreases

  Bond ionically creating a soluble white solid

  alkali metal + water -> metal hydroxide + hydrogen

  alkali metal + chlorine -> metal chloride
• Halogens - Group 7


  Going down the group:

  • reactivity decreases
  • Melting/boiling point increases
  • Fluorine - poisonous, yellow gas
  • Chlorine - poisonous, dense, green gas
  • Bromine - dense, poisonous, red-brown volatile liquid OR orange vapour
  • Iodine - poisonous, dark grey, crystalline solid OR purple vapour
• Noble Gases - group 0


  Going down the group:

  • boiling point increases
• Transition elements


  Vs Alkali metals (group 1):

  • higher melting point
  • less reactive
  • harder
  • denser

  Good catalysts
• Ionic bonds are held together by electrostatic attraction
• Simple molecular substances have low melting and boiling points due to weak Inter-molecular forces but they increase with size of the molecule
• Metallic bonding


  Electrostatic attraction between positive ions and negative delocalised electrons
• Sizes of particles

  • nano particles - 1nm - 100nm -> between 10 and 1000 atoms across
  • fine particles - 100nm - 2500nm
  • coarse/dust - 2500nm - 10000nm
• Things to consider when choosing a process:


  1. Atom economy
  2. Percentage yield
  3. Rate of reaction
  4. Equilibrium position
  5. Usefulness of by-products
• acid + alkali -> salt + water

  Ionic equation:

  H+ + OH- -> H2O
• Strength of acids


  Strong acids are more reactive. A strong acid dissociates fully in water / fully ionises.

  H+ ions are released

  Weak acids only slightly ionise

  Lower pH = a higher concentration of H+ ions in solution
• Electrolysis

  Reduction occurs at negative cathode with oxidation occurring at positive anode

  In solution:

  • Least reactive positive ion is electrolysed at the cathode. As it is more reactive it is more likely to stay as an ion
  • At the positive anode - the halide ion is electrolysed if present, if not, OH- is electrolysed

  4OH- -> O2 + 2H2O + 4e-

  When electrolysing aluminium ore (bauxite), molten cryolite is added to reduce melting point to 900°C
• Energy change in a reaction

  Total energy change = energy of bond breaking - energy of bond making

  If the change is negative - exothermic

  If the change is positive - endothermic
• Cells and batteries

  • Bigger the difference between the reactivity of the electrodes, the bigger the voltage
  • voltage also depends upon concentration of ions in the electrolyte solution
• Fuel cells

  A fuel and oxygen react. Fuel enters and is oxidised creating a potential difference

  (in hydrogen-oxygen fuel cells) - H+ ions move through electrolyte to the positive cathode.

  At the cathode, oxygen gains electrons and reacts with H+ ions producing water

  2H2 + O2 -> 2H2O