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C4 Revision. Best used in conjunction with program C4Helpers. Acids and bases - basics. pH below 7 7 above 7 acid neutral alkali Only solutions can have a pH Use words “increase” and “decrease” Acids HCl, HNO 3 , H 2 SO 4 Bases: metal oxides, hydroxides, carbonates

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C4 revision l.jpg

C4 Revision

Best used in conjunction with program C4Helpers

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Acids and bases - basics

  • pH below 7 7 above 7

  • acid neutral alkali

  • Only solutions can have a pH

  • Use words “increase” and “decrease”

  • Acids HCl, HNO3, H2SO4

  • Bases: metal oxides, hydroxides, carbonates

  • Alkalis are bases that dissolve

  • Salts are made in neutralisations of acid by alkali (or vice-versa)

  • Indicators change colour with pH.

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  • Acid + base  salt + water

  • Salt is named from metal in the base + ending from the acid:

  • Chlorides from hydrochloric

  • Sulphates from sulphuric

  • Nitrates from nitric

  • Produce word equations for making salts

  • Carbonates give CO2 too.

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Higher tier

  • Acids release H+(aq) ions

  • Alkalis release OH-(aq) ions

  • Neutralisation: H+ + OH- H2O

  • Produce symbol equations for making salts by neutralisation

  • E.g.

  • 2NaOH + H2SO4 Na2SO4 + H2O

  • 2HCl + MgO  MgCl2 + H2O

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Reacting quantities - basics

  • Read atomic mass from periodic table

  • Read formulas to see how many of which atoms

  • Add atomic masses to get formula mass (simple)

  • More reactants make more product

  • Mass after reaction must equal mass at start

  • Percentage yield is what’s actually made, could be reasons for this to be less than predicted

    • Losses in evaporation, filtration, transfers.

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Reacting quantities - more

  • Formula mass – more difficult with brackets

  • Scale-up quantities, e.g. double reactants gives double products

  • Percentage yield = actual yield x 100 predicted yield

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  • Calculate product amounts given reactant amounts

  • Think percentages or proportions

  • The sums will be simple. Honest.

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  • Crops grow better – faster, better quality

  • Minerals absorbed through roots

  • Spot N, P, K in formulas (e.g. KNO3, (NH4)3PO4)

  • State names of nitrogenous fertilisers from nitric acid, e.g. ammonium nitrate (NH4NO3)

  • Fertilisers made by neutralisation

  • Recognise burette in diagrams

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  • Must dissolve

  • Increase yield

  • Given formula, calculate relative formula mass Mr

  • Which acid and alkali make which fertilisers, see acids above.

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  • Fertilisers add minerals to depleted soils

  • More N incorporated into plants so more growth

  • Eutrophication sequence:

    • 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.

  • Be able to calculate the percentage mass of a particular element in a fertiliser

  • Describe a way to make the fertiliser

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  • Ammonia is made from nitrogen and hydrogen.

  • Nitrogen for the manufacture of ammonia by the Haber process is obtained from air.

  • Hydrogen for it often comes from the cracking of oil fractions or from natural gas.

  • Recognise thatÝ is used to represent a reversible reaction. One which can proceed in both directions.

  • Describe some uses of ammonia:

    • manufacture of fertilisers;

    • manufacture of nitric acid;

    • in cleaning fluids.

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  • Describe how ammonia is made in the Haber process:

    • nitrogen + hydrogen ammonia;

    • iron catalyst;

    • high pressure;

    • temperature in the region of 450oC;

    • unreacted nitrogen and hydrogen are recycled.

  • Recognise the importance of ammonia in relation to world food production.

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Higher tier

  • Explain the use of the conditions used in the Haber process:

    • high pressure increases the percentage yield of ammonia;

    • high temperature decreases the percentage yield of ammonia;

    • high temperature gives a high rate of reaction;

    • 450°C is an optimum (compromise) temperature to give a fast reaction with a sufficiently high percentage yield;

  • Catalyst increases rate of reaction but does not change the percentage yield.

  • Balanced equation for the manufacture of ammonia in the Haber process:

  • N2 + 3H2Ý 2NH3

  • FOR ALL INDUSTRIAL PROCESSES: Economic considerations determine the conditions used :

    • rate must be high enough to give a sufficient daily yield of product;

    • percentage yield must be high enough to give a sufficient daily yield of product;

    • a low percentage yield can be accepted if the reaction can be repeated many times with recycled starter materials;

  • Optimum conditions used that give the lowest cost rather than the fastest reaction or highest percentage yield.

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Industrial chemistry

  • Describe that the cost of making a new substance

  • depends on:

    • price of energy (gas and electricity);

    • cost of starting material;

    • wages (labour costs);

    • equipment (plant);

    • how quickly the new substance can be made (cost of catalyst).

  • (Higher)

  • Interpret tables and graphs relating to percentage yield in reversible reactions and changed conditions. (No recall required).

  • Interpret data about rate, percentage yield and costs for alternative industrial processes (No recall required).

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  • Describe the function of each ingredient in a washing powder:

    • active detergent does cleaning;

    • water softener to soften hard water;

    • bleaches to remove coloured stains;

    • optical brighteners to give the “whiter than white” appearance;

    • enzymes used in low temperature washes to remove food stains.

  • Predict the correct washing conditions using the wash label.

  • Terms solvent, solute, solution, soluble and insoluble.

  • Recognise that different solvents will dissolve different substances.

  • Correct solvent to remove a stain given appropriate information.

  • Many detergents are salts.

  • Describe the function of each ingredient in a washing-up liquid:

    • active detergent does the cleaning;

    • water to thin out detergent so it can be dispensed easily;

    • colouring agent and fragrance to improve attractiveness of product;

    • rinse agent to help water to drain off crockery;

    • water softener to soften hard water.

  • Interpret data from experiments on the effectiveness of washing up liquids and washing powders.

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  • Advantages - low temperature washes

    • energy saving

    • the type of clothes - damaged by water

  • Dry cleaning - process used to clean clothes that does not involve water:

    • solvent that is not water;

    • stain will not dissolve in water.

  • Describe that many detergents are made by the neutralisation of acids with alkalis.

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  • Chemical nature of a detergent and how detergents work:

    • hydrophilic head;

    • hydrophobic tail.

  • Intermolecular forces, how a dry cleaning solvent removes stains.

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Batch or continuous?

  • Recall that ammonia is made all the time in a continuous process.

  • Describe that speciality chemicals such as medicines and pharmaceutical drugs are often made on demand in a batch process

  • State that the factors that affect the cost of making and developing a medicine or pharmaceutical drug include:

    • research and testing;

    • labour costs;

    • energy costs;

    • raw materials;

    • time taken for development;

    • marketing.

  • Raw materials for speciality chemicals such as pharmaceuticals can be either made synthetically or extracted from plants

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  • Relatively small scale production of pharmaceutical drugs - large scale industrial manufacture of ammonia.

  • Factors contributing to the high costs involved in making and developing a new medicine or pharmaceutical drug:

    • 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.

  • Chemicals are extracted from plant sources:

    • crushing;

    • dissolving in suitable solvent;

    • Chromatography / crystallisation

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  • “Evaluate the advantages and disadvantages of batch and continuous manufacturing processes given relevant data and information.”

  • Economic considerations determine the development of new drugs in relation to:

    • research and development time and associated labour costs;

    • time required to meet legal requirements including timescale for testing and human trials;

    • anticipated demand for new product;

    • length of pay back time for initial investment.

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  • You researched this.

  • May need to know:

    • Physical and chemical properties of graphite, diamond and buckyballs

    • Read the revision guide

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Water Purity (Foundation level)

  • Water resources in the United Kingdom:

    • lakes;

    • rivers;

    • aquifers;

    • reservoirs.

  • Important resource for industrial chemical processes:

    • a cheap raw material;

    • as a coolant;

    • as a solvent.

  • Pollutants in domestic water supplies:

    • nitrate residues;

    • lead compounds;

    • pesticide residues.

  • Types of substances present in water before it is purified:

    • dissolved salts and minerals;

    • microbes;

    • pollutants;

    • insoluble materials.

  • Chlorination kills microbes in water.

  • Barium chloride solution to test for sulphate ions - gives a white ppt.

  • Silver nitrate solution to test for halide ions:

    • chloride ions give a white ppt;

    • bromide ions give a cream ppt;

    • iodide ions give a pale yellow ppt.

+ Water in the developing World - Explain the importance of clean water for people in

the developing nations.

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  • Interpret data about water resources in the United Kingdom (no recall is expected).

  • Explain why it is important to conserve water.

  • Recall the source of pollutants in water:

    • • nitrate from fertiliser run off;

    • • lead compounds from lead pipes;

    • • pesticide from spraying near to water resources

  • Describe the water purification process to include filtration, sedimentation and chlorination.

  • Testing of water with aqueous silver nitrate and barium chloride solutions.

  • Word equations for the precipitation reactions of barium chloride with sulphates and silver nitrate with halides.

    • Barium chloride with sulphates

    • Silver nitrate with halides

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  • Explain processes in water purification.

  • Explain that some soluble substances are not removed from water during purification and that these may be poisonous.

  • Explain the disadvantages of using distillation of sea water to make large quantities of fresh water.

  • Given the appropriate formulae:

  • Barium chloride with sulphates:

  • BaCl2 + MgSO4 MgCl2 + BaSO4

  • Silver nitrate with chlorides:

  • AgNO3 + NaCl  AgCl + NaNO3

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The End

  • Good Luck.