OCR ChemistryModuleC4CHEMICAL ECONOMICS
C4–Fundamental chemical concepts
Word equationsin terms of reactant and products
Symbol equationsbalanced symbol equations using formulae (some or all with brackets) of thereactants and products
Formula with bracketsstate number/type of atoms in the formula
Formulas – recallHCl; HNO3; H2SO4; NH4OH; CaCO3; CuO; KOH; Na2CO3; NaOH; KCl; NaCl; NH4Cl; Na2SO4; K2SO4; (NH4)2SO4;
AgNO3; AgCl; BaCl2; BaSO4
Molecular formulainvolving a shared pair ofelectrons
Displayed formulashows both theatoms and the covalent bonds in a molecule
C4a Acids and Bases
pH scale0-6 (acid); 7 (neutral); 8-14 (alkali)
Universal indicatoruse of colours to indicate pH
Neutralisationacid + base salt + water
Neutralisation – ionic equationH+ + OH- H2O
Alkalisoluble base
Acidin solution contains hydrogen ions (H+)
Alkaliin solution contains hydroxide ions (OH-)
Basemetal oxides; metal hydroxides
Carbonates – neutralisationacid + carbonate a salt + carbon dioxide + water
Salts from acidssulphuric (sulphates); nitric (nitrate); hydrochloric (chloride)
C4b Reacting Masses
Relative atomic masslook up data from Periodic Table
Relative formula masscalculate from a formula using relative atomic masses
Conservation of massthe total mass of reactants at the start ofa reaction is equal to the total mass of productsmade
% yielda way of comparingamount of product made (actual yield) to amountexpected (predicted yield)
% yield – calculation% yield = actual yield X 100 ÷ predicted yield
Loss of yieldloss in filtration; loss in evaporation; loss in transferring liquids; loss in heating
C4c Fertilisers and crop yield
Fertiliserssoluble; 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
Eutrophicationrun-off of fertiliser; increase of nitrate or phosphate in riverwater;algal bloom; blocks off sunlight to other plants
which die; aerobic bacteria use up oxygen; most living organisms die
Percentage by masscalculate percentage by mass of each essentialelement in a fertiliser given its formula and theappropriate
relative atomic masses
Acid/alkali combinationsneeded to make: ammonium nitrate; ammonium phosphate; ammonium sulphate; potassium nitrate.
Preparation of fertilisernames of reactants; experimental method; how a neutral solution is obtained; how solid fertiliser is obtained
C4d Making ammonia – Haber Process and Costs
Ammoniaimportance in relation toworld food production.
Haber processnitrogen + hydrogen ammonia
Symbol equationN2 + 3H2 2NH3
Conditionsiron catalyst; high pressure; temperature (450°C); unreacted N2 and H2 are recycled
High pressureincreases the percentage yield of ammonia
High temperaturedecreases the percentage yield; gives a high rate of reaction;450°C is optimum temperature to give afast
reaction with a sufficiently high percentage yield
Catalystincreases the rate of reaction butdoes not change the percentage yield
Cost of new substancehigher pressure higher plantcost;higher temperature higher energy cost;catalysts reduce costs by increasing the
rate of reaction; recycling unreacted starting materials reduces costs;automation reduces wages bill
Manufacture – economicsrate high enough to give asufficient daily yield; percentage yield high enough togive a sufficient daily yield;
low percentage yield can be accepted ifreaction can be repeated many timeswith recycled started materials;
optimum conditions give thelowest cost rather than the fastest reaction or highest percentage yield
C4e Detergents
Detergent ingredientsactive detergent (cleaning); water softener (soften hard water); bleaches (remove coloured stains): optical
brighteners (give the whiter than white appearance);enzymes (low temperature washesremove food stains)
Low temp. washenergy saving and the type ofclothes that can be washed
Detergent moleculehydrophilic head attracts water); hydrophobic tail (attracts fat/grease)
Dry cleaningcleaning clothes without involving water; solvent that is not water; stain will not dissolve in water
Stain removalsolvent overcomes intermolecular forces
Detergents – saltsmany detergents are made by theneutralisation of acids with alkalis
C4f Batch or Continuous?
Continuous processe.g. production of ammonia; continuous production; runs automatically; consistent quality; high start-up cost
Batch processe.g. use of fermenter; usually smaller quantities; time delay between batches; labour intensive; low start-up cost
Drug developmentresearch and testing; labour costs; energy costs; raw materials; time taken for development; marketing
Development/manufactureoften more labour intensive; less automation possible; research and testing may take many years; raw materials
likely to be rare and/or involveexpensive extraction from plants;legislative demands
Development – decisionresearch/development time; labour costs;time for legal requirements; time for testing/human trials;
anticipated demand for new product;length of pay back time for initialinvestment
Plant extractionchemicals extracted; crushing; dissolving in suitable solvent; chromatography
C4g Nanochemistry
Allotropesdifferent structural forms of the same chemical element; carbon allotropes: diamond/graphite/buckminster
fullerene
Diamond – usescutting tools (very hard and high melting point); jewellery (lustrous and colourless)
Diamond – structurenot conduct electricity (nofree electrons); hard/high melting point (presence of many strong covalentbonds)
Graphite – usespencil leads (slippery/black); lubricant (slippery); electrode in electrolysis (conducts electricity high melting point)
Graphite – structureconducts electricity (delocalised electrons that can move); slippery (layers of carbon atomsweakly held together
can slide easily over each other); high melting point (manystrong covalent bonds to break)
Buckminster fullereneC60; can ‘cage’ other molecules; deliver drugs
Nanotubes – usessemiconductors in electrical circuits;industrial catalysts; reinforce graphite in tennis rackets; catalysts
Nanotubes – as catalystscatalyst attached to nanotubes; large surface area available
Nanoparticlesdifferent properties from the ‘bulk’ chemical
Molecular manufacturemolecule-by-molecule building of a product; uses positional chemistry or by starting with a biggerstructure and
then removing matter to producenanoscale features
C4h How pure is our water?
Drinking waterpollutants that may be found indomestic water supplies:nitrate residues; lead compounds; pesticide residues
Pollution sourcesnitrate from fertiliser run off;lead compounds from lead pipes;pesticide from spraying near to water resources
Water conservationwater as a limited resource
Water purificationfiltration, sedimentation and chlorination
Filtrationscreen out leaves/twigs/fish; gravel/sand beds filter out smaller particles
Sedimentationfiner particles settled out using aluminium sulphate
Chlorinationkills bacteria
Sea waterdistillation ofsea water to make large quantities of fresh water; high energy cost
Precipitate (ppt)cloudy insoluble solid
Silver nitratetest forhalide ions: chloride ion(Cl-) white ppt; bromide ion (Br-) cream ppt; iodide ion (I-) pale yellow ppt
Barium chloridetestfor sulphate ions (SO42-: gives a white ppt
Developing nationsmany people have poor drinking water/limited access to clean drinking water; disease problems