C7


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  • Depending on the value of a chemical, the chemical industry makes them on different scales. Eg Bulk chemicals are things such as ammonia, sulphuric acid, sodium hydroxide. Are made on a large scale. Fine chemicals such as drugs, food additives and fragrances are made on a small scale.
    • Chemists are required to follow standard procedures, carry out a titration, scale up production, interpret results and carry out quality assurance.
    • C7
      • The production of chemicals includes; preparation of starting materials (feedstocks), synthesis, separation of products, handling of by-products and waste and monitoring purity.
      • Catalysts are used to speed up reacitons. By reducind the activation energy needed for a reaction. This means it goes faster at a lower temperature. They are also reusable as they don't change during the reaction.
      • To make esters you: 1. Ethanol and ethanoic acid are heated under reflux. So it's constantly evaporated and condensated. Basically heated and returned to the flask as condensation once evaporated. This happens with sulphuric acid. 2. The ester is removed through distillation. The liquid is turned into gas and removed from the mixture. 3. The gas (the distillate) is purified. Sodium carbonate is added and the mixture gets shaken. it reacts with any remaining acid and extracts it into the aqueous phase. The aqueous phase is then removed. 4. the product is then put in a conical flask and calcium chloride is added to remove water. The calcium chloride is removed through filtration as it's a solid.
      • Activation energy is the energy needed in a reaction to break down bonds and start a reaction.
      • When hydrogen is burned in oxygen it makes water. Hydrogen reacts with halogens to make hydrogen halides. Eg hydrogen chloride.
      • Nitrogen is needed in plants to make nitrate ions. Some bacteria can make nitrates at room temperature and pressure by using enzymes as catalysts. However these natural processes can't make enough nitrates to grow sufficient food for the world's population.
      • Stages of qauntitative analysis. 1.Choose an analytic method that corresponds with the bulk material. 2. measure out the sample. 3. If solid, dissolve it. 4. Measure a property of a solution that's proportional to the chemical in the sample. 5. calculate a value using these's measurements. 6. Compare values to find range, work out the average and state confidence in results.
        • Qualitative analysis is any method that is used to find chemicals in a substance. Quantitative analysis is any method used to find the amount of a chemical in a substance.
          • After a sample for analysis has been collected, it should be stored in a clean and sterile container. Then sealed, labelled and stored safely. This will increase reliability of the analysis.
          • C7
            • The production of chemicals includes; preparation of starting materials (feedstocks), synthesis, separation of products, handling of by-products and waste and monitoring purity.
            • Catalysts are used to speed up reacitons. By reducind the activation energy needed for a reaction. This means it goes faster at a lower temperature. They are also reusable as they don't change during the reaction.
            • To make esters you: 1. Ethanol and ethanoic acid are heated under reflux. So it's constantly evaporated and condensated. Basically heated and returned to the flask as condensation once evaporated. This happens with sulphuric acid. 2. The ester is removed through distillation. The liquid is turned into gas and removed from the mixture. 3. The gas (the distillate) is purified. Sodium carbonate is added and the mixture gets shaken. it reacts with any remaining acid and extracts it into the aqueous phase. The aqueous phase is then removed. 4. the product is then put in a conical flask and calcium chloride is added to remove water. The calcium chloride is removed through filtration as it's a solid.
            • Activation energy is the energy needed in a reaction to break down bonds and start a reaction.
            • When hydrogen is burned in oxygen it makes water. Hydrogen reacts with halogens to make hydrogen halides. Eg hydrogen chloride.
            • Nitrogen is needed in plants to make nitrate ions. Some bacteria can make nitrates at room temperature and pressure by using enzymes as catalysts. However these natural processes can't make enough nitrates to grow sufficient food for the world's population.
            • Stages of qauntitative analysis. 1.Choose an analytic method that corresponds with the bulk material. 2. measure out the sample. 3. If solid, dissolve it. 4. Measure a property of a solution that's proportional to the chemical in the sample. 5. calculate a value using these's measurements. 6. Compare values to find range, work out the average and state confidence in results.
              • Qualitative analysis is any method that is used to find chemicals in a substance. Quantitative analysis is any method used to find the amount of a chemical in a substance.
                • After a sample for analysis has been collected, it should be stored in a clean and sterile container. Then sealed, labelled and stored safely. This will increase reliability of the analysis.
            • Titration's are used to see how much acid is needed to neutralise an alkali. It's an important form of quantitative analysis. Here are the steps; 1.Fill a burette with acid. 2. Use a pipette to measure 25cm^3 of aqueous alkali and put in conical flask. Add some indicator / phenolphthalein. And put flask under burette on a white tile. 4. Slowly add the acid to flask while mixing. when the phenolphthalein goes clear the alkali is neutralised. 4. Record the volume of acid added. 5. Repeat until two results are the same.
              • A pH probe can be used instead of an indicator to measure the change in pH. It will produce a pH/volume graph. From this graph you can find the volume of acid added and the end point of the reaction (where it's neutralised.)
                • To calculate the concentration of an acid or an alkali from a titration you must ; 1. Work out the mean of your results (the average acid added) 2. use this formula concentration of acid (g/dm^3) = volume of alkali (dm^3) x concentration of alkali (g/dm^3) x 0.9125 / volume of acid (dm^3). You have to work in dm^3 so if it's cm just divide it by 1000
      • Titration's are used to see how much acid is needed to neutralise an alkali. It's an important form of quantitative analysis. Here are the steps; 1.Fill a burette with acid. 2. Use a pipette to measure 25cm^3 of aqueous alkali and put in conical flask. Add some indicator / phenolphthalein. And put flask under burette on a white tile. 4. Slowly add the acid to flask while mixing. when the phenolphthalein goes clear the alkali is neutralised. 4. Record the volume of acid added. 5. Repeat until two results are the same.
        • A pH probe can be used instead of an indicator to measure the change in pH. It will produce a pH/volume graph. From this graph you can find the volume of acid added and the end point of the reaction (where it's neutralised.)
          • To calculate the concentration of an acid or an alkali from a titration you must ; 1. Work out the mean of your results (the average acid added) 2. use this formula concentration of acid (g/dm^3) = volume of alkali (dm^3) x concentration of alkali (g/dm^3) x 0.9125 / volume of acid (dm^3). You have to work in dm^3 so if it's cm just divide it by 1000
  • Governments have a duty to protect people and the enviornment. There are strict regulations to control chemical processes, storage of chemicals and transportation of chemicals.
    • In the UK a health and safety executive (HSE) will regulate risks to health and safety. Eg labelling all hazardous chemicals.
  • Green chemistry is based on things that can lead to more sustainable processes.
    • A sustainable chemical process depends on; the atom economy, the use of renewable sources, energy inputs and outputs, health and safety risks, waste prevention, the impact on the environment and social and economic benefits.
      • Atom economy is the amount of reactants that end up as useful products. Atom economy = mass of atom in the useful produce / total mass of atoms in reactant x 100
        • The final product should contain all the atoms in the process and reduce waste products and increase yield.
          • The yield percentage of a product can be calculated using this formula. Percentage yield = actual yield / theoretical yield x 100.
            • Renewable products should be used where possible. Several companies are starting to use plants however they take up a lot of land. Fertilisers can improve productivity however they use a lot of energy during manufactur-ing.
              • The energy needed for a reaction should be minimized. Reactions should also be carried out at a good temperature and pressure to reduce energy needed.
                • Substances in chemical processes need to be carefully selected to minimise the risk of accidents. Not using hazardous chemicals can also reduce impacts on the environment.
                  • Social benefits of green chemistry are; cleaner air, cleaner buildings and improved water quality. Economic benefits is that it costs less for the energy.
  • Finding the mass of a product; 1. Work out the RFM of each substance. 2. check that the mass of reactants matches the mass of products as nothing should be gained or lost. 3. Write the ratio of the reactants to the product you are working out the mass for. Not all the products, just the one you need to know the mass of. Eg if the RFM of the reactants in 56 and the RFM of the cerain product is 25. The ratio will be 56:25. 4. Use that ratio to work out how much is made. If you need to need to know how much is made with 50kg of reactant you would do 56 / 25 x 50. If it was 75ml of reactant, you'd times by 75. The unit doesn't effect the result.
    • Finding the mass of a reactant: 1. Work out the RFMs. 2. Check the masses are equal. 3. Ignore any substances not mentioned in the question and write a ratio of reactant to product. 4. Then work out how much is needed to get the certain amount of product. If the ratio is 56:25, reactant to product. Put the reactant on top 56 / 25 times by the figure given. eg if you need to work out how much reactant is needed to get 540 tonne of product, times by 540.
  • Alkanes are hydrocarbons. The carbon atoms are joined together by single carbon-carbon bonds. They're saturated as they only contain single bonds. They won't react with aqeous solutions as the bonds are strong so unreactive. However they burn well in sir to make carbon dioxide and water.
    • There are also alkenes. Which are hydrocarbons but the carbons have double bonds c=c so they're unsaturated.
  • All alcohols contain the functional group; -OH. The two simplest alcohols are methanol and ethanol.
    • Methanol can be used as a chemical feedstock and in cosmetics. Ethanol can be used as a solvent and as a fuel.
      • Shorter alcohols have a lower boiling point as their intermolecu-lar forces are weak and don't need much energy to overcome. Longer alcohols/ hydrocarbons are less soluble as they're more like alkanes so tend to float due to their low density.
        • When alcohols react with sodium they produce a salt and hydrogen. Eg ethanol + sodium = sodium chloride + hydrogen
          • Alkanes, water and alcohols react differently with sodium.
            • Sodium sinks when in alcohol, doesn't melt and gives off hydrogen as a product.
            • Sodium floats on water, melts, rushes around and gives off hydrogen as a product rapidly.
            • Sodium doesn't react with alkanes.
  • Ethanol can be produces by synthesis, fermentation and biotechnology. It is used industrially as feedstock, solvent and fuel. Synthesis uses fossil fuels as a raw material.
    • Synthesis makes ethene which can be used to make ethanol. 1. the crude oil undergoes fractional distillation. 2. Long chain hydrocarbons (alkanes) are vaporised and cracked using a catalyst and heat. 3. the molecules are purified using fractional distillation. 4. the ethene produced has any remaining water removed and can be used as feedstock. Ethene is then reacted with steam at high temperatures and pressures with a catalyst to make ethanol. ethene + steam = ethanol.
      • Fermentation makes ethanol for alcoholic drinks. 1. water and yeast are mixed with raw materials (natural sugars) at just above room temperature. 2. enzymes found in yeast act as a catalyst and make ethanol and carbon dioxide. The carbon dioxide can escape the reaction vessel but air can't enter it. Glucose = Ethanol + carbon dioxide.
        • When ethanol is made with fermentation the amount made is limited by the amount of sugar used and above a certain concentration the ethanol can kill the yeast. You can make more ethanol after fermentation by distilling the mixture. The distillation process makes spirits.
        • Optimum fermentation conditions are needed otherwise at a temperature too high the enzymes in the yeast are denatured and the same if the pH is too high. If there is oxygen, the oxygen becomes oxidised to make ethanoic acid. Aka vinegar.
        • Biotechnol-ogy uses genetically modifies E.coli bacteria and waste biomass. The E.coli have genes which allow them to digest the sugars in the biomass and convert them into ethanol. This means that a lot of waste such as wood, corn stalks etc. Can be used to make ethanol instead of staying as waste. The optimum conditions are at a temperature of 25-37 degrees. And the pH to remain constant as to not denature the enzymes.
  • Carboxylic acids have the functional group -COOH. Examples of carboxylic acids are methanoic acid and ethanoic acid. Most have horrible smells and tastes.
    • They're weak acids which means that they're less reactive than stronger acids and their pH's are higher than stronger acids. They react with metals and alkalis to make salts. When reacting with metals they form salt and hydrogen. When reacting with carbonates they form salt, water and carbon dioxide. Alkalis can also neutralise them.
      • When a carboxylic acid reacts with an alcohol they will form an ester. The reaction is carried out with a strong acidic catalyst. The reaction has a by product of water.
        • Esters have very distinctive smells which are used for fruit flavours and smells. They're also used for perfumes. Esters can be found in solvents and plasticizers.
  • Fats and oils are naturally occuring esters. Fats are the esters of glycerol and fatty acids.
    • Animals fats are mostly saturated as they only contain single bonds and are unreactive.
      • Vegetable oils are mostly unsaturated as they contain double bonds and are more reactive.
  • An exothermic reaction is a chemical reaction that gives energy (often heat) to the surroundings. This energy change can be shown on an energy-level diagram. In this reaction, bonds are made.
    • In endothermic reactions, energy is taken in from the reactions. They're less common than exothermic reactions. In an endothermic reaction bonds are broken down.
    • Some reactions are reversible. This is shown with a double headed arrow when drawn in an equation.
      • A reversible reaction will reach dynamic equilibrium. Dynamic equilibrium is when there's a steady state. The forwards and backwards reactions happen at the same rate. Eg when people are at a shop, as long as someone enters when a person leaves there will always be the same amount of people in the shop.
    • The Haber process uses nitrogen from the air and hydrogen to make ammonia. This is a reversible reaction. Because of this, only a small amount of gas that leaves the reaction is actually ammonia. Un-reacted nitrogen and hydrogen are reused, this improves the yield. This is economically better than waiting for the reactants to be used up in dynamic equilibrium.
      • Ammonia can be used for fertilisers, explosives, dyes, medicines and many other essential chemicals.
        • To increase the rate of the Haber process, scientists are looking for new catalysts to mimic natural enzymes. Stronger equipment is needed to increase pressure which will increase the yield however costs more. And may be a health and safety issue. They use a pressure that compromises between cost and yield so may not be the most effective. If you increase the temperature, it will increase the reaction rate but will decrease the yield. The temperature is a compromise between yield and rate of reaction. The catalyst will sped up the reaction without affecting the yield.
      • Chormatogra-phy is used to find out what unknown mixtures are made up of. When substances move through the stationary phase, they're split up and move at different speeds. They're also dissolved in the mobile phase to allow them to move up the stationary phase.
        • The solvent used in the mobile phase is aqueous (water based) or non-aqueous (organic liquids eg alkanes.) The stationary phase is the medium the solvent moves through, which is mostly paper.
          • A dynamic equilibrium is set up between the phases.
          • Paper chromatogra-phy has 5 main stages; 1. if the substance is solid, dissolve it in the solvent. 2.Place a spot of the solution on the chromatogra-phy paper. 3. Place the bottom of the paper into some solvent. 4. As the solvent travels up the paper it will dissolve the solution. 5. The chemicals in the mixture will separate because they're molecularly different.
            • Layer chromatopgra-phy is similar to paper but the stationary phase is a thin absorbent material. Eg silica gel.Which is supported by a flat, unreactive surface. Eg glass. Advantages of this method are; it runs faster, the mobile phases moves more, you can choose different absorbencies for the stationary phase.
              • In gas chromatogra-phy, the mobile phase is a carrier gas, the stationary phase is a microscopic layer of liquid on an unreactive solid, the liquid is inside glass/ metal tubing called a column.
                • A sample of the substance is injected into one end of the column (Which is heated and filled with the liquid stationary phase) where it gets vaporised and the carrier gas carries it to where separation happens,
                  • The substance in then separated into separate components because of their different solubilities.
                    • Advantages of gas chromatogra-phy include; better at seperating substances, can produce quantitative data from very small samples. Uses of it include; detecting banned substances and analysing oil spills to indentitfy sources of pollution.
                      • Gas chromatogr-ams show the relative amount of each chemical. This is shown by the size of the peaks, the bigger the peak the more of that chemical.
                        • Retention time is how long it takes each substance to pass through the system.
          • A chromatogram is formed when the chemicals bind to the stationary phase. This can then be compared to a standard chromatogram to see what chemicals are contained in the substance. Some need locating agents for colourless substances. This may be UV rays or a chemical that reacts with the spots colouration.
            • The movement of the substance in comparison to the movement of the substance is known as Rf value. To work this out you use the formula; Rf value = distance travelled by solute / distance travelled by solvent.
      • Standard solutions can be used to measure concentrations of other solutions. Measured in g/dm^3.
        • To make a standard solution you; 1.Weigh out 5g of solid sample in beaker. 2. put sample in volumetric flask using short stem funnel. Wash funnel and beaker with distilled water. Pour the used distilled water into flask to make sure all the solid sample was transferred. 3. Add more distilled water to flask till 3 quarters full. Seal top with stopper and gently shake until dissolved. 4. Place flask on level surface and fill with normal water till the solution reaches 100cm^3. 5. Invert the flask.
          • To calculate the concentration of the solution you need to use this formula; concentration (g/dm^3) = mass (g) of solute / volume (dm^3) of solution
      • How valid an experiment is depends on the accuracy of the results. Mistakes can include; misreading scales, not filling burette to correct level, taking a thermometer out of the solution to read the temperature.
        • Accuracy is how close the result is to the 'actual' value. Precision is how spread out the values are, how big the range is. A large range leads to uncertainty.
          • Two measures of uncertainty are systematic errors and random errors.
            • Systematic errors are when the repeated measurements are consistently too high or too low.
            • Random errors are when repeated measurements give different values, or one of errors (outliers.)

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