Chemistry 4 Notes

C4A – Acids and Bases •Sulphuric acid is used to clean metal plates •The pH scale Red – Strong Acid Yellow/Orange – Weak Acid Green – Neutral Blue/Purple – Weak Alkali Purple – Alkali •Neutralisation A base is a solid that reacts with acids acid + base →

salt

+

water

H2SO4 (Sulphuric Acid) + 2NaOH (Sodium Hydroxide) → Na2SO4 (Sodium Sulphate) + 2H2O (Water)

All acids in solution with water contain hydrogen ions (H+) All alkalis in solution with water contain hydroxide ions (OH-) •More on bases Metal oxides and hydroxides are always bases Hydrochloric acid + Copper (II) hydroxide → Copper(II) chloride + Water Ammonia is also a base Carbonates can also neutralise acids, but carbon dioxide is also made Hydrochloric acid + Calcium carbonate → Calcium Chloride + Carbon Dioxide + Water

C4B – Reacting Masses •No mass is lost in any chemical reaction •In a candle, mass is changed into water (hydrogen+oxygen) and carbon dioxide (carbon+oxygen) •This can be tested with soda lime as these elements are trapped in it and the total mass of the candle and soda lime will always be equal •The mass of products is always equal to the mass of reactants •Relative formula mass The bottom number on the periodic table is the atomic number The top number is the relative atomic mass We can work out the relative formula mass from the relative atomic mass •Yield Predicted Yield is the maximum possible amount of yield Actual Yield is the actual yield Percentage Yield = Actual Yield/Predicted Yield x 100 C4C – Fertilisers and Crop Yield •Fertilisers are used to replace essential elements removed by previous crops •Overuse of nitrogen-containing fertilisers causes eutrophication Rain water causes fertiliser to run into rivers Nitrate/Phosphate concentration in the water increases Microscopic water plants (Algae) grow at an accelerated rate (Algal Bloom) Dense algae prevents sunlight reaching underwater plants and they die, also killing the nutrients of the algae

Bacteria feed on the dead plants and use all the oxygen in the water All other fish and water life dies due to no oxygen •Nutrients and plant growth Plants need minerals to grow These are replaced by fertilisers Fertilisers also add nitrogen, phosphorus and potassium to help growth Minerals must be soluble as they are taken in through the roots in water Nitrogen is used for protein and helps growth increase and speeds it up NH4NO3 (Ammonium Nitrate) is a good fertiliser as it contains a lot of nitrogen and is very soluble Mineral uptake can be lowered if the soil is too acidic/alkaline An acid and an alkali make a fertiliser and are separated by filtration and evaporation •Examples of Fertilisers Nitric Acid + Ammonia = Ammonium Nitrate Sulphuric acid + Ammonia = Ammonium Sulphate Phosphoric Acid + Ammonia = Ammonium Phosphate Nitric Acid + Potassium Hydroxide = Potassium Nitrate These are mixed to produce NPK C4D – Reversible Reactions •The Haber Process Nitrogen and Hydrogen are mixed to make ammonia The following conditions are applied Temperature around 450oC – Too high will encourage decomposition, but a high enough temperature increases the rate of reaction A high pressure – encourages the formation of ammonia An iron catalyst – speeds up the reaction This is a reversible reaction •Costs Higher temperatures need more energy Higher pressures need thicker containers and more money spent on materials Catalysts cost to buy, but save fuel costs and time in speeding up the reaction Reactions can be automated, so people do not have to be paid to control the system Two factors are required in the system Cheap production for competition Large yield to increase profit

C4E – Detergents •Water is the most common solvent, but not everything dissolves in it •Water molecules have small positive and negative charges so they dissolve substances which also have positive and negative charges •They do not attract substances without a charge

•Washing powders are a complex mixture of ingredients The active detergent does all the cleaning and are often made by a neutralisation Some use soap which is less damaging to delicate fibres Some use synthetic detergents (soap-less) and are better at cleaning •Detergent molecules Have charge hydrophilic heads Have uncharged hydrophobic tails The hydrophobic tails link to the stain and then pull them towards the water •Soap is made by the neutralisation of fatty acids and alkalis The acids have long chains of hydrogen and carbon and form the hydrophobic tail Saponification - When a fatty acid with glycerol (triglyceride) reacts with sodium hydroxide, a sodium salt is formed (soap) The charged sodium adds to the hydrophilic head Synthetic detergents are made by neutralising a synthetic acid with an alkali to form a molecule similar to soap, but with stronger detergent properties •Other ingredients Water softeners for hard water areas – Stops clothes being covered in scum and means less detergent is used Bleach can be used to remove coloured stains Optical brighteners make clothes very bright Bio detergents are detergents with enzymes (biological catalysts) that break down the stains They will denature at high temperatures C4F – Batch or Continuous? •Developing a pharmaceutical drug or medicine is a long, costly process •It can take £300,000,000 and 15 years to develop •Discovery→Phase 1: Test on Animals→Phase 2 : Test on human volunteers→Phase 3 : Clinical Trial→Marketing

•Drugs must be legalised and must be marketed which also costs •Many drugs cannot be automated in production, which can cost •Manufacture can require a lot of energy •Extracting chemicals Extraction from plants has many stages Crush Plants Mix with solvent Filter Purify Evaporate Solvent DRUG Use chromatography to test for impurities •Decisions to be made before producing the drug Cost of research and development Time taken to reach legal requirements Demand for the product

How long will it take for profits to repay the investment •Batch or Continuous The Haber process is continuous Continuous processes are used when there is a constant demand and are called bulk chemicals Many products are made by batch and are called speciality chemicals C4G – Nano chemistry •Different forms of carbon such as graphite and diamond are called 'allotropes' •Diamond – Transparent, very hard, very high melting point, insulator, lustrous with a brilliant shine •Graphite – Opaque and black, soft and slippery, high melting point, conducts electricity, lustrous •Structures Diamond All carbon atoms are joined to four others by strong covalent bonds There are no ions or free electrons Graphite Atoms are in layers Strong bonds within layers Weak bonds between layers Electrons are delocalised so it can conduct electricity Buckminsterfullerene Made of 60 carbon atoms joined together Each molecule is called a “Bucky” ball Other fullerenes have been discovered since Nanotubes Fullerenes joined together make tube shapes called nanotubes in a new area of study called nanotechnology They are very strong and can conduct electricity •Semiconductors in electrical circuits •Industrial Catalysts •A reinforcement for tennis racquets They have a large surface area so they are good for attaching catalysts •Nanochemistry was born with nanotubes It works with materials at an atomic level and works with small particles called nanoparticles They are the only particle that can act as a true metallic conductor The spacing and size of nanotubes can make them act like semiconductors such as silicon •Caging molecules It is possible to trap molecules or cage them inside nanotubes They could be used to inject into the bloodstream to prevent cancer as medicine •Making molecules could be done (molecular manufacture) by using nanotubes to precisely position parts (positional chemistry)

C4H – How pure is our water? •Tap water is impure, but the chemicals are harmless to us •Water pollutants include: Nitrate Residues – Get in the water when rain dissolves fertilisers into rivers Lead compounds - Can dissolve into water from lead pipes Pesticide residues – From farmers spraying too close to rivers and lakes •In developing nations where water is not purified, it contains disease-causing microbes •Water is used as: A cheap raw material for manufacture A coolant A solvent •Purification is important to remove: Microbes Dissolved salt and minerals Pollutants Insoluble materials •Purification process Water goes to the sedimentation tank to allow large materials to settle Then it goes to filtration which traps finer materials Finally it goes through chlorination where microbes are killed Not all impurities are gone, but most are harmless and at low concentration •Seawater is often distilled for homes and is 3% salt Distilled water is tasteless as it is pure Distillation costs a lot •Water is often tested for chemicals by precipitation •A precipitate will make the water cloudy if there is an impurity Three halides form precipitates with different colours Silver Chloride – White Silver Bromide – Cream Silver Iodide – Yellow •An example reaction Sodium Chloride + Silver Nitrate → Sodium Nitrate + Silver Chloride