Chemistry 2

Chemistry 2

2A - Bonding and Calculations
1. Bonding
  1. Ionic
    1. Transferring electrons
    2. Ionic compounds have...
      1. High melting point
        When molten, there are FREE ELECTRONS
        Conducts electricity when in solution, but not when solid
      2. Regular lattice structure
      3. Strong attraction between ions
  2. Covalent
    1. Share electrons
      1. Each covalent bond provides each atom with one extra electron
    2. EXAMPLES
      1. Water (H20)
      2. HYDROGEN (H2)
      3. AMMONIA (NH3)
    3. TWO TYPES
      1. Molecular substances
        STRONG bonds to form SMALL molecules
        WEAK attraction between molecules
        LOW melting point
        EXAMPLE: Oxygen
      2. Giant structures
        ALL atoms bonded together by STRONG bonds
        HIGH Melting points
        DON'T conduct electicity
        EXAMPLE: Diamond
2. Materials
  1. ALLOYS - Different sized atoms displace layers of metal atoms, meaning they cant slide over eachother, making allows harder than normal metals.
  2. METALLIC STRUCTURES
    1. Free electrons
    2. Regular structure
  3. Nanoparticles
    1. Fullerens (Bucky Balls)
      1. Made of carbon atoms
    2. Nanotubes
  4. Polymers
    1. Strong covalent bonds hold the atoms together in chains
    2. Thermosoftening - No cross linking chains, weak attraction between chain, easy to melt and can be remoulded as many times as you like
    3. Thermosetting - Crosslinks between the chains, holding them together in solid structure. Tough, hard and rigid
3. Atoms!
  1. TOP number is Atomic Mass
  2. BOTTOM number is number of protons
  3. ISOTOPES are atoms with THE SAME amount on protons, and DIFFERENT amounts of neutrons
  4. RELATIVE FORMULA MASS is all the relative atomic masses of all the atoms in that compound added together
2B - Reaction Rates, Salts and Electrolysis
1. Measuring ROR
  1. Amount of reactant used or amount of product formed DIVIDED BY time
  2. Precipitation - When a solution becomes cloudy - the faster it becomes cloudy, that faster the ROR
  3. Change in mass (usually gas given off) - Do your gassy reaction on some scales, the faster the mass drops, the faster the reaction, this is very accurate and easy to measure
  4. Volume of gas given off - Measured by a gas syringe, the more gas given off in a given amount of time, the faster the reaction.
2. Collision Theory
  1. Higher temperature, concentration and surface area increase the number of collisions between particles, speeding up the rate of reaction
3. Catalysts
  1. A catalyst is a substance which speeds up a reaction without being changed or used up in the reaction.
  2. These can reduce costs in industry!
4. Energy Transfer in Reactions
  1. Exothermic releases heat
    1. Combustion
    2. Neutralisation reactions (acid and alkali)
  2. Endothermic takes in heat
    1. Much less common
    2. Thermal decomposition, eg heat must be added to make calcium carbonate decompose to make quicklime CaCO3 --> CaO + CO2
5. Acids and Alkalis
  1. Acids and Bases neutralise eachother
    1. Metal Oxides and Hydroxides are bases
  2. Alkali is a base that dissolves in water
  3. Acid + Base = Salt + Water
  4. Acid + Metal = Salt + Hydrogen
6. Electrolysis
  1. "Splitting up with electricity"
  2. Passing current through ionic solution splits up the ions, positive ions going to the Cathode, and negative ions going to the Anode.
  3. PANIC - Positive Anode, Negative Is Cathode
  4. REDUCTION is the GAIN of electrons
    1. OXIDATION is the LOSS of electrons
      1. OIL RIG - Oxidation Is Loss, Reduction Is Gain
        Reduction happens on the Cathode
        Oxidation happens on the Anode
  5. Used to extract Aluminium from its ore
  6. Cryolite is used to lower the temperature (and the costs)
  7. Electroplating
    1. Replace the cathode with something to be electroplated, and is will be coated in a layer of the metal ions in the electrolyte
    2. Used with Silver (jewellery)
    3. Used with Copper (Electronics)
7. ROR depends on 4 Things
  1. Temperature
  2. Concentration
  3. Catalyst
  4. Surface area
KEY
1. ROR - Rate of Reaction
2. EXAMPLE
3. Ar - Atomic Mass
4. Mr - Formula mass
5. IMPORTANT
Calculations
1. % mass of an element in a compound
  1. Ar MULTIPLIED BY No. of atoms (of the element) THEN DIVIDE BY Mr (Of whole compound ) THEN MULTIPLY BY 100
2. Empirical Formula
  1. Look it up, it wont fit into this mind map...
3. Percentage yield = Actual yield DIVIDED BY predicted yield

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