OCR Chemistry Module C4 CHEMICAL ECONOMICS
C4 – Fundamental chemical concepts
Word equations
Symbol equations
Formula with brackets
Formulas – recall
Molecular formula
Displayed formula
in terms of reactant and products
balanced symbol equations using formulae (some or all with brackets) of the reactants and products
state number/type of atoms in the formula
HCl; HNO3; H2SO4; NH4OH; CaCO3; CuO; KOH; Na2CO3; NaOH; KCl; NaCl; NH4Cl; Na2SO4; K2SO4; (NH4)2SO4;
AgNO3; AgCl; BaCl2; BaSO4
involving a shared pair of electrons
shows both the atoms and the covalent bonds in a molecule
C4a Acids and Bases
pH scale
Universal indicator
Neutralisation
Neutralisation – ionic equation
Alkali
Acid
Alkali
Base
Carbonates – neutralisation
Salts from acids
0-6 (acid); 7 (neutral); 8-14 (alkali)
use of colours to indicate pH
acid + base  salt + water
H+ + OH-  H2O
soluble base
in solution contains hydrogen ions (H+)
in solution contains hydroxide ions (OH-)
metal oxides; metal hydroxides
acid + carbonate  a salt + carbon dioxide + water
sulphuric (sulphates); nitric (nitrate); hydrochloric (chloride)
C4b Reacting Masses
Relative atomic mass
Relative formula mass
Conservation of mass
% yield
% yield – calculation
Loss of yield
look up data from Periodic Table
calculate from a formula using relative atomic masses
the total mass of reactants at the start of a reaction is equal to the total mass of products made
a way of comparing amount of product made (actual yield) to amount expected (predicted yield)
% yield = actual yield X 100 ÷ predicted yield
loss in filtration; loss in evaporation; loss in transferring liquids; loss in heating
C4c Fertilisers and crop yield
Fertilisers
Eutrophication
Percentage by mass
Acid/alkali combinations
Preparation of fertiliser
soluble; increase crop yield; replaces essential elements used by previous crop or provides extra essential
elements; more nitrogen gets incorporated into plant protein so increased growth
run-off of fertiliser; increase of nitrate or phosphate in river water; algal bloom; blocks off sunlight to other plants
which die; aerobic bacteria use up oxygen; most living organisms die
calculate percentage by mass of each essential element in a fertiliser given its formula and the appropriate
relative atomic masses
needed to make: ammonium nitrate; ammonium phosphate; ammonium sulphate; potassium nitrate.
names of reactants; experimental method; how a neutral solution is obtained; how solid fertiliser is obtained
C4d Making ammonia – Haber Process and Costs
Ammonia
importance in relation to world food production.
Haber process
nitrogen + hydrogen
Symbol equation
Conditions
High pressure
High temperature
N2 + 3H2
2NH3
iron catalyst; high pressure; temperature (450°C); unreacted N2 and H2 are recycled
increases the percentage yield of ammonia
decreases the percentage yield; gives a high rate of reaction; 450°C is optimum temperature to give a fast
reaction with a sufficiently high percentage yield
increases the rate of reaction but does not change the percentage yield
higher pressure higher plant cost; higher temperature higher energy cost; catalysts reduce costs by increasing the
rate of reaction; recycling unreacted starting materials reduces costs; automation reduces wages bill
rate high enough to give a sufficient daily yield; percentage yield high enough to give a sufficient daily yield;
low percentage yield can be accepted if reaction can be repeated many times with recycled started materials;
optimum conditions give the lowest cost rather than the fastest reaction or highest percentage yield
Catalyst
Cost of new substance
Manufacture – economics
C4e Detergents
Detergent ingredients
Low temp. wash
Detergent molecule
Dry cleaning
Stain removal
Detergents – salts
C4f Batch or Continuous?
Continuous process
Batch process
Drug development
Development/manufacture
Development – decision
Plant extraction
ammonia
active detergent (cleaning); water softener (soften hard water); bleaches (remove coloured stains): optical
brighteners (give the whiter than white appearance); enzymes (low temperature washes remove food stains)
energy saving and the type of clothes that can be washed
hydrophilic head attracts water); hydrophobic tail (attracts fat/grease)
cleaning clothes without involving water; solvent that is not water; stain will not dissolve in water
solvent overcomes intermolecular forces
many detergents are made by the neutralisation of acids with alkalis
e.g. production of ammonia; continuous production; runs automatically; consistent quality; high start-up cost
e.g. use of fermenter; usually smaller quantities; time delay between batches; labour intensive; low start-up cost
research and testing; labour costs; energy costs; raw materials; time taken for development; marketing
often more labour intensive; less automation possible; research and testing may take many years; raw materials
likely to be rare and/or involve expensive extraction from plants; legislative demands
research/development time; labour costs; time for legal requirements; time for testing/human trials;
anticipated demand for new product; length of pay back time for initial investment
chemicals extracted; crushing; dissolving in suitable solvent; chromatography
C4g Nanochemistry
Allotropes
Diamond – uses
Diamond – structure
Graphite – uses
Graphite – structure
Buckminster fullerene
Nanotubes – uses
Nanotubes – as catalysts
Nanoparticles
Molecular manufacture
C4h How pure is our water?
Drinking water
Pollution sources
Water conservation
Water purification
Filtration
Sedimentation
Chlorination
Sea water
Precipitate (ppt)
Silver nitrate
Barium chloride
Developing nations
different structural forms of the same chemical element; carbon allotropes: diamond/graphite/buckminster
fullerene
cutting tools (very hard and high melting point); jewellery (lustrous and colourless)
not conduct electricity (no free electrons); hard/high melting point (presence of many strong covalent bonds)
pencil leads (slippery/black); lubricant (slippery); electrode in electrolysis (conducts electricity high melting point)
conducts electricity (delocalised electrons that can move); slippery (layers of carbon atoms weakly held together
can slide easily over each other); high melting point (many strong covalent bonds to break)
C60; can ‘cage’ other molecules; deliver drugs
semiconductors in electrical circuits; industrial catalysts; reinforce graphite in tennis rackets; catalysts
catalyst attached to nanotubes; large surface area available
different properties from the ‘bulk’ chemical
molecule-by-molecule building of a product; uses positional chemistry or by starting with a bigger structure and
then removing matter to produce nanoscale features
pollutants that may be found in domestic water supplies: nitrate residues; lead compounds; pesticide residues
nitrate from fertiliser run off; lead compounds from lead pipes; pesticide from spraying near to water resources
water as a limited resource
filtration, sedimentation and chlorination
screen out leaves/twigs/fish; gravel/sand beds filter out smaller particles
finer particles settled out using aluminium sulphate
kills bacteria
distillation of sea water to make large quantities of fresh water; high energy cost
cloudy insoluble solid
test for halide ions: chloride ion (Cl-) white ppt; bromide ion (Br-) cream ppt; iodide ion (I-) pale yellow ppt
test for sulphate ions (SO42-: gives a white ppt
many people have poor drinking water/limited access to clean drinking water; disease problems