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Unit 3 Higher

Unit 3 Higher. Chemical Industry. Raw materials – straight from the earth e.g. air, sea water, rocks, crude oil, metal ores Feedstocks – prepared from raw materials e.g. naphtha, nitrogen, oxygen Costs – capital – plant set up - fixed – don’t fluctuate e.g. wage

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Unit 3 Higher

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  1. Unit 3 Higher

  2. Chemical Industry • Raw materials – straight from the earth e.g. air, sea water, rocks, crude oil, metal ores • Feedstocks – prepared from raw materials e.g. naphtha, nitrogen, oxygen • Costs – capital – plant set up - fixed – don’t fluctuate e.g. wage - variable e.g. transport, fuel, electricity • Profit – increased by recycling, selling excess energy • Position – good access to raw materials, transport links, work force

  3. Hess’s Law “the enthalpy change is independent of the route taken” e.g.

  4. Equilibrium forward and backward reaction rates become equal, concentrations of reactants and products constant but not equal!

  5. Shifting the Equilibrium concentration - increase [A], equilibrium moves to decrease [A], moves right, more C and D. Watch for neutralisers and precipitators (eg Ag, Pb, Ba)!! temperature - increase , equilibrium moves towards the endothermic side (H +), to the left, less C and D pressure - increase, equilibrium moves towards the side with less moles of gas, to the right, more C and D catalyst - no effect on the position of the equilibrium

  6. Acids and bases The pH Scale 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 acid neutral alkali in pure water H2O (l) H+(aq) + OH-(aq) [H+(aq)] = [OH-(aq)] = 10-7 mol l-1 pH = 7 [H+(aq)] = 10-x mol l-1 pH = x Ionic product of water, [H+(aq)] x [OH-(aq)] = 10-14mol2 l-2

  7. Strong and weak acids Strong – completely ionise/dissociate in water e.g. HCl (aq) H+ (aq) + Cl- (aq) Weak – only partially ionises in water e.g. CH3COOH (aq) CH3COO-(aq) + H+(aq) Strong – more H+ ions, more acidic, lower pH, better conductor, react quicker BUT same volume of alkali needed to neutralise each; same final volume of hydrogen produced on reaction with reactive metal.

  8. Strong and weak alkalis Strong – completely ionise/dissociate in water e.g. NaOH (aq) Na+ (aq) + OH- (aq) Weak – only partially ionises in water e.g. NH4OH (aq) NH4+(aq) + OH-(aq) Strong – more OH- ions, more alkaline, higher pH, better conductor BUT same volume of acid needed to neutralise each p12 data book shows weak acids and alkalis

  9. pH of salts H2O (l) H+(aq) + OH-(aq) Weak acid removes H+, excess OH- so pH>7 Weak alkali removes OH-, excess H+ so pH<7

  10. Redox Chemistry OILRIG Oxidation is loss of electrons Reduction is gain of electrons p11 data book Redox – reduction and oxidation occurring together Oxidising agent lets something else be oxidised, is itself reduced Reducing agent lets something else be reduced, is itself oxidised

  11. Redox Chemistry Titrations Balance reduction/oxidation equations – get same number of electrons by multiplying Look at mole ratio of each reactant in balanced redox equation Use n = cV to work out concentrations (V in litres) Use m = n x gfm to work out mass

  12. Redox Chemistry Electrolysis Q (C) = I (A) x t (s) 1 F = 96,500C = quantity of electricity associated with 1 mole of electrons Reduction or oxidation equation (p11) relates moles of element to moles of electrons and hence charge 1 mole of an element = gfm; 1 mole = 24 litres gas e.g. 2H+ + 2e- H2 2 x 96,500C 2 g or 24 litres

  13. Radioactivity

  14. Radioactivity Half-life The half-life for a radioisotope is the time it takes for the radioactivity to decrease by half.

  15. Radioactivity Uses of radioisotopes Medical - cobalt-60 (g) deep seated tumours; - iodine-131 (b)thyroid function - phosphorous-32 (b)skin cancer Industry - cobalt-60 (g)check welds in steel and food irradiation - americium-241 (a) smoke detectors

  16. Radioactivity Uses of radioactivity Production of energy – nuclear fission sets off a chain reaction - nuclear fusion – in stars

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