C7: Further Chemistry

Organic Compounds
1. Organic Molecules and Functional Groups
  1. Alkanes
    1. ALKANES: a family of hydrocarbons
      1. methane
      2. ethane
      3. propane
      4. butane
    2. made up of chains of carbon atoms surrounded by hydrogen atoms
    3. all have the formula CₓH₂ₓ+₂, where x is the number of carbon atoms in the chain
    4. only contain single covalent bonds between carbon atoms - they're SATURATED compounds
      1. in UNSTAURATED compounds, there are carbon to carbon (C=C) bonds
    5. burn to give carbon dioxide and water
      1. alkane + oxygen → carbon dioxide + water
    6. don't react with most chemicals
      1. don't react with aqueous reagents
        AQUEOUS REAGENTS: substances dissolved in water
      2. don't react because the C—C and C—H bonds in them are difficult to break
  2. alcohols have an -OH functional group and end in '-ol'
    1. all alcohols have similar properties because they all have the -OH functional group
2. Alcohols
  1. Alcohols
  2. the general formula for an alcohol is CₓH₂ₓ₊₁OH
    1. x again represents the number of carbon atoms in the chain
  3. I need to know the first two alcohols...
    1. methanol
      1. CH₃OH
      2. used in the chemical industry as a starting point for the manufacture of other chemicals
    2. ethanol
      1. C₂H₅OH
      2. can be made by fermentation
      3. used in perfumes and aftershave lotions, as it can mix with both the oils, which gives it the smell, and the water, which makes up the bulk
      4. can be made from biomass
  4. react with sodium
    1. sodium + water → sodium ethoxide + hydrogen
    2. although much less vigorously than with water
    3. unlike alkanes
  5. burn in air to produce carbon dioxide and water
    1. ∵ ils contient hydrocarbon chains
3. Carboxylic Acids
  1. all have the functional group -COOH
    1. this gives them all similar properties
  2. their names start with start with the usual meth/eth/prop/but and end in -anioc acid
  3. 1. Жишээ нь:
      1. methanoic acid
        HCOOH
        aka formic acid
      2. ethanoic acid
        CH₃COOH
        aka acetic acid
  4. react with stuff like other acids
    1. carboxylic acid + metal → salt + hydrogen
      1. ethanoic acid + magnesium → magnesium ethanoate
    2. carboxylic acid + carbonate → salt + water + carbon dioxide
    3. carboxylic acid + alkali → salt + water
  5. are weak acids - less reactive than strong acids like HCl, H₂SO₄
  6. have strong smells and tastes
    1. vinegar, dilute ethanoic acid, is an example of this
4. Esters
  1. esters have the functional group -COO-
  2. formed when carboxylic acids react with alcohols in the presence of a strong acid catalyst
  3. production of esters
  4. uses
    1. often used in flavourings and perfumes
      1. many have sweet and fruity tastes and smells
      2. volatile, so they're good for perfumes, as the molecules evaporate easily, so can drift into the smell receptors of your nose
    2. also used as solvents for paint, glue, ink and in nail varnish remover
  5. fats and oils are esters of glycerol and fatty acids
    1. fatty acids = carboxylic acids with long chains (≈ 16 to 20 carbons)
      1. fatty acids can be saturated (only C—C bonds) or unsaturated (C=C bonds)
    2. glycerol = an alcohol
    3. plants and animals make fats and oils to store excess energy
      1. animal fats are mainly saturated, vegetable fats mainly unsaturated
Analysis
1. Analytical Procedures
  1. QUALITATIVE analysis tells you what a sample contans
  2. QUANTITATIVE analysis tells you how much of a substance a sample contains
  3. chemical analysis is carried out on SAMPLES, ∵...
    1. it might be hard to test all of a material if you've got lotsa it
    2. if something goes wrong, you'll still be able to go back, take another sample and try again
  4. samples are analysed in solution
    1. if the solvent is water, it's aqueous, if not, it's non-aqueous
  5. STANDARD PROCEDURE: everyone does everything the same way
    1. scientists within companies, nations, or international groups agree to all use the same methods of working
      1. the methods chosen are deemed the safest, most effective and most accurate
    2. there are standard procedures for the collection, storage and analysis of samples
2. Chromatography
  1. uses TWO PHASES
    1. the MOBILE phase
    2. the STATIONARY phase
  2. CHROMATOGRAPHY: an analytical method used to separate then identify the substances in a mixture
3. Solution Concentrations
  1. concentration = mass (of solute) ÷ volume (of solution)
    1. concentration is measured in grams per dm³
      1. 1 dm³ = 1 litre = 1000 cm³
  2. a STANDARD SOLUTION = any solution that you know the concentration of
4. Titration
  1. the main stages of a quantitative titration analysis are as follows...
    1. measuring out accurately a specific mass or volume of the sample
      1. working with replicate samples
        dissolving the samples quantitatively
        measuring a property of the solution quantitatively
        calculating a value from the measurements
        estimating the degree of uncertainty in the results
  2. titrations are used to check the purity of an acid or alkaline product
Green Chemistry
1. The Chemical Industry
  1. lots and lots of chemicals are made for lots and lots of different things on different scales...
    1. BULK
      1. produced on a large scale, 例如...
        ammonia
        sulfuric acid
        sodium hydroxide
        phosphoric acid
    2. fine
      1. produced on a small scale, მაგალითად...
        medicines
        fragrances
        food additives
  2. new chemical products need lots of RESEARCH
    1. before new chemical products are made, huge amounts of research has to be done
      1. this can take years and years and be more expensive than a return train ticket to Scotland, but will all be worth it in the end
    2. مثلا, to make a new production process run efficiently, a catalyst may need to be found, involving the following processes...
      1. testing potential catalysts using trial and error
        making computer models of the reaction to work out which substance might work as a catalyst
        designing or refining the manufacture of the catalyst to ensure the safe, efficient and cost effective mass-production of the catalyst
        investigating the risks to the environment posed by using the new catalyst and trying to minimise them
  3. GOVERNMENT REGULATIONS protect people and the environment
    1. this is done to protect workers, the general public and the environment
    2. mar shampla, there are regulations about...
      1. USING CHEMICALS
        näiteks, sulfuric acid is sprayed on potato fields to destroy the leaves and stems of the plant, making it easier to harvest them
        government regulations restrict how much acid can be used and require signs to be displayed to warn the public
      2. STORAGE
        many dangerous chemicals must be kept in locked storerooms
        poisonous chemicals must be stored in either sealed containers or well ventilated store cupboards
      3. TRANSPORT
        lorries transporting chemicals that could be dangerous must display hazard symbols and identification numbers to help the emergency services to deal with any accidents or spills
2. Characteristics of Green Chemistry
  1. there are several stages in the production of useful chemicals:
    1. 1: the preparation of feedstocks
      1. this requires raw materials, the naturally occurring substances which are needed, til dæmis...
        crude oil
        natural gas
      2. FEEDSTOCKS: the actual reactants needed for the process, kwa mfano...
        hydrogen
        ethanol
      3. the raw materials usually have to be purified in some way to make the feedstocks
      4. 2: synthesis
        the feedstocks (id est reactants) are converted in to products using way cool science stuff
        the conditions must be carefully controlled to ensure that the reaction happens at a sensible rate
        3: separation of products
        chemical reactions, as magic as they are, usually produce the substance that you want plus some other chemicals, known as by-products
        sometimes there are also some reactants let over that didn't get used
        everything has to be separated out so that the different chemicals can be dealt with in different ways
        4: monitoring the purity of the product
        even after everyone has tried their best to separate everything out, there may still be some other bits and bobs mixed in with the 'final' product, ∴ it's not completely pure
        for this reason, the product has to be monitored to ensure that it stay between certain levels
        different industries need different levels of purity, depending on wat the product's going to be used for...
        if a product is going to end up inside people (id est medicines, nakadhalika), it should be pretty pure
        if a slightly impure product will be fine for the job, there's no point wasting time and money on purification, especially if you've never been to France. France is great.
        5: handling of by-products and wastes
        où possible, waste products are sold or used in another reaction
        if the reaction is exothermic, there may be waste heat
        heat exchangers can use excess heat to produce steam or hot water for other reactions, saving energy and money
        waste products must be carefully disposed of so that they don't harm other people or the environment
        there are legal requirements about this
        scientists, eg Carlos, must be very cautious when approaching wheat by-products
  2. there are eight key questions about SUSTAINABILITY...
    1. will the raw material run out?
    2. how good is the atom economy?
    3. what do I do with the waste products?
    4. what are the energy costs?
    5. will it damage the environment?
    6. what are the health and safety risks?
    7. any there any benefits or risks to society?
    8. is it profitable?
Energy Changes
1. Energy Transfer
  1. energy is always SUPPLIED to BREAK bonds
    1. ergo bond breaking is an ENDOthermic process - energy must be supplied
    2. and bond forming is an EXOthermic process - energy is released
    3. so in EXOTHERMIC reactions, the energy released by forming bonds is greater than the energy used to break them
    4. and in ENDOTHERMIC reactions, the energy supplied to break the bonds is greater than the energy released by bonds forming
2. Bond Energies
  1. every chemical bond (isibonelo H — H) has a particular bond energy associated with it
    1. the bond energy varies slightly depending on the compound the bond occurs in
    2. one can use these known bond energies to calculate the overall energy change of a reaction
      1. one uses the following formula:
        overall energy = energy required to - energy released change break bonds by forming bonds
3. Catalysts
  1. activation energy is needed to start a reaction
    1. this can be lowered by using a catayst
  2. some industrial reactions use enzyme catalysts
Reversible Reactions and Equilibria
1. Reversible Reactions
  1. a REVERSIBLE REACTION: a reaction where the products of the reaction can themselves react to produce the original reactants
    1. A + B ⇌ C + D
  2. the Haber Process is a reversible reaction used to produce ammonia
    1. N₂(g) + 3H₂(g) ⇌ 2NH₃(g) (+ heat)
    2. the feedstocks for the process are nitrogen and hydrogen
      1. the nitrogen is obtained from the air, which is 78% nitrogen
      2. the hydrogen comes from the cracking of chemicals in natural gas using steam
    3. ammonia is used in the manufacture of fertilisers, explosives, dyes, medicines and a variety of other chemicals
    4. the reaction is carried out under certain conditions to make it as efficient as possible...
      1. pressure: 200 atmospheres
      2. temperature: 450°C
      3. catalyst: iron
    5. nitrogen fixation is a process that turns the N₂ in the air into ammonia
      1. the Haber Process is a non-biological way of fixing nitrogen
2. Equilibria
  1. if a reversible reaction takes place in a closed system, so that none of the reactants can escape, a state of dynamic equilibrium will always be reached
  2. EQUILIBRIUM: when the relative (%) quantities of reactants and products will reach a certain balance and stay there
    1. when this happens, there may still be reactions going on, but the forward and backwards reactions will be happening at the same rate - this is called DYNAMIC EQIULIBRIUM

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C7: Further Chemistry

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