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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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Chemical industry
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


Unit 3 higher

Hess’s Law

“the enthalpy change is independent of the route taken”

e.g.


Equilibrium
Equilibrium

forward and backward reaction rates become equal,

concentrations of reactants and products

constant but not equal!


Unit 3 higher

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


Acids and bases
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


Strong and weak acids
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.


Strong and weak alkalis
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


Ph of salts
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


Redox chemistry
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


Redox chemistry1
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


Redox chemistry2
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



Radioactivity1
Radioactivity

Half-life

The half-life for a radioisotope is the time it takes for

the radioactivity to decrease by half.


Radioactivity2
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


Radioactivity3
Radioactivity

Uses of radioactivity

Production of energy – nuclear fission

sets off a chain reaction

- nuclear fusion – in stars