Chemistry C2

Chemistry C2

Relative Atomic Mass (AR)
1. The weight of isotope 1 * the amount we have + The weight of isotope 2 * the amount we have.
2. DIVIDED BY
3. How much in total we actually have
Molecular Mass (Mr)
1. All you do is add up the mass!!!
2. C = 12 , H = 1
  1. C2 H4
    1. 12 + 12 + 1 + 1 + 1 + 1 = 28.
Percentage Composition (Yeild)
1. ---------------------------------------------------------------------
2. PY= Total Ar of the element you are finding
3. Mr of the compound
4. * 100
Empirical Formula
1. 1. Divide each mass % by the Ar of itself.
2. 2. Times these decimals to get whole numbers.
3. 3. Place in eg. CuFeS2
Quantities Of Elements
1. 1. First Balance the equation given.
  1. 2. Now work out the Mr of the equation incorporating the balances (ignoring the big numbers)
    1. 3. Now times them by BIG numbers
      1. 4. Now Divide opposite of what question is asking (in question) by what you got in the calculation.
        5. Now times this by the number after the -> to get the answer.
Ionic Bonding.
1. When a metal reacts with a non metal.
  1. Metal atom looses electrons and becomes POSITIVE
    1. Non-metal gains electrons and becomes NEGATIVE
      1. The oppositely charged electrons attract.
Covalent Bonding
1. When two non-metals combine they share electrons
  1. They do this to obtain a full outer shell.
  2. Oxygen atoms share two electrons with another oxygen to make a double bond.
2. Very Strong
3. Cannot dissolve in water
4. Weak intermolecular forces = easily broken down
Giant Covalent Lattices
1. Diamond
  1. Tetraheidroid
  2. Hardest natural substance
  3. Non conductive
  4. 4 Covalent bonds = very durable
2. Graphite
  1. Soft, used as a lubricant
  2. Conductive
  3. No covalent bonds, they can slide over each other
3. Silicone dioxide
  1. Very Hard
  2. Used as sandpaper
  3. Non Conductive
Metallic Properties
1. Alloys = STRONGER
2. Alloys are the mixture of two or more meals.
  1. In pure metal, all atop are the same size and therefore are very soft meaning the atoms can slide.
    1. Alloys disrupt the regular lattice due to the range of sizes.
3. Imagine the inside of an atom as circles, there will be bigger and smaller circles.
  1. If you push this it will be harder than all the same size.
Gas Chromatography
1. Allows a mixture of compounds to be separated, by their weight
  1. 1. Sample dissolved in solvent an then injected into an end of the column
    1. 2. Unreactive gas (nitrogen) carries same through column
      1. 3. Diff. substances travel through column at different speeds, and thus become separated
        4. Separeted substances leave the column, one after another. as they leave , they are detected by a detector
2. Long glass tube, packed with solid powered material, fitted into an oven
Rates of Reaction
1. ROR = Amount of product formed
2. DIVIDED BY
3. Time taken
4. Can be increased by:
  1. Increasing the temp.
    1. Concentration
    2. Preassure
  2. Catylist
  3. Smaller particles
Endothermic
1. Heat enters and gets cooler.
  1. The energy is usually transferred as heat energy, causing the reaction mixture and its surroundings to get colder.
    1. Examples
      1. The thermal decomposition of calcium carbonate in a flash furnace
      2. The reaction between ethnic acid and sodium carbonate
      3. Electrolysis
Exothermic
1. Heat leaves and gets hotter
  1. The energy is usually transferred as heat energy, causing the reaction mixture and its surroundings to become hotter.
    1. Examples
      1. Burning
      2. Neutralisation Reactions between acids and alkalis
      3. The reaction between water and calcium odide
Electrolysis
1. When an ionic substance is melted or dissolved in water, the ions are free to move around within the liquid or solution
2. The positively charged ions move towards the negative electrode and are reduced.
3. The negatively charged ions move toward the positive electrode and are oxidised
4. The electrolysis of sodium chloride solution produces hydrogen, sodium hydroxide and chlorine
Thermosoftening
1. Soften when heated and can be shaped when hot. The shape will then harden when it is cooled, but can be reshaped when heated again. poly(ethene) is thermosoftening polymer, tangled polymer chains can uncoil and slide past each other, making it a flexible material
2. Thermosetting
  1. Once moulded, they do not soften when heated and they cannot be reshaped. Vulcanised rubber is a thermoset used to make tyres. Its polymer chains are joined together by cross-links, so they cannot slide past each other easily
Collision Theory
1. The reactants must collide to form a chemical reaction.Increasing the temperature provides particles with more energy so they vibrate more resulting in more collisions
  1. To cause a reaction, the particles must collide with sufficient energy to break bonds. This minimum energy is called activation energy
Catylists
1. Chemicals that are used to speed up relations in a reaction but do not get used up in the process.
  1. They lower the activation energy, so that more collisions occur at a faster rate, without having to build up a higher minimum energy.

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