The Chemical Industry
Bulk chemicals- made on a large scale. Fine chemicals-made on a small scale.
The production of chemicals involves:
- Prep of feedstocks
- seperation of products
- handling of waste
- monitering purity
Chemical industries have to try and be Green. They can do this by using renewable feedstocks and calculating atom economy.
Atom economy= mass of atoms in product produced/total mass of reactants
Catalysts are used in chemical industry to speed up reactions. They reduce activation energy needed to react so it is faster and lowers the temp needed. Sometimes enzyme catalysts are used so these need to be kept at a set temp and Ph.
Alkanes, alkenes and alcohols
Alkanes are hydrocarbons, made out of carbon and hydrogen atoms, with single bonds.They are called saturated hydrocarbons.
Alkenes are also hydrocarbons but with double bonds, they are called unsaturated hydrocarbons. They are more reactive than alkanes as they have double bonds so can bond more.
Alcohols are made up of carbon, hydrogen and OH atoms. They have weak forces between molecules as they have exposed electrons. Ethanol is one of the simplest alcohols and can be produced by either synthesis, fermentation or biotechnology.
Synthesis- alkanes are vaporised to produce ethene, then are reacted with steam to produce ethanol.
Fermentation- Water and yeast and mixed with glucose and enzymes in the yeast are a catalyst for the ethanol and CO2. CO2 escapes but air doesnt enter the reaction.
Biotechnology- this uses genetically modified E-coli bacteria and waste biomass. The bacteria digest the biomass and turn it into ethanol.
Carboxylic acids and Esters
Carboxylic acids are made up of carbon, hydrogen, CO and OH atoms. They are weak acids and are less reactive than other acids. They react with metals, carbonates and alkalis to produce acid salts.
Carboxylic acids react with alcohol with a strong catalyst to form esters. Esters have distinctive smells and are used in food products and plasticizers.
Fats and oils are naturally occuring esters; animal fats are saturated molecules (single bond) and vegetable oils are unsaturated molecules (double bonds).
How to make Esters-
Ethanol and ethanoic acid are heated under reflux, then the ester is removed by distillation. Then, the distillate is purified to make sure all molecules have reacted, then it is filtered to get rid of any excess water.
Exothermic reactions= release energy as products have less energy than reactants did.
Endothermic reactions- take in energy as reactants had less energy than products do.
Activation energy= the energy it takes to break bonds to start a reaction. Breaking bonds is an endothermic reaction and making bonds is a exothermic reaction. So,for example... if a reaction takes more energy in to break bonds than releasing to make bonds, that reaction is endothermic.
You can work out whether a reaction is exothermic or endothermic by making calculations about the bonds broken and made and how much energy (J) is used to do this.
Reversible reactions= when the products can react together to form the reactants. Ammonia is a good example of this.
Dynamic equilibrium= when the forwards and backwards reactions in a reversible reaction are going at the same rate.The conccentration of reactants and products doesnt change.
Examples of chemistry
The Haber Process- this is when nitrogen is converted into ammonia by reacting it with hydrogen gas. This is a reversible reaction. Unreacted hydrogen and nitrogen are recycled to improve the yield.
If you increase the temp of this process, the rate of reaction will increase BUT the dynamic equilibrium will be pushed to the left so the yield will decrease. If you increase pressure, the reactants are pushed together so yield will increase BUT it would be very expensive to do this. A catalyst speeds up the reaction but doesnt effect yield.
Chromatography - used to find out whats in unknown mixtures. Substances are seperated in the stationary phase(what it moves through) at different speeds, while dissolved in the mobile phase. Solvents which move the solution are called the mobile phase (water-based).
Thin layer chromatography- a thin layer of absorbant material can be used as opposed to paper. This is better as the solvent and the dissolved substances run better and can move more.
R1 value= distance travelled by substance/ distance travelled by solvent
R1 value is the movement of a substance reletive to the movement of the solvent.
Gas Chromatography and Standard solutions
GC is when the stationary phase is a layer of liquid on a solid support and the mobile phase is a carrier gas. The substance can be injected into the heated column, where it vaporises then the different components are seperated. These gases are detected and analysed to see how much is in the substance of each component.
Retention time= the time taken for each substance to go through the chromographic system.
Its when you know exactly what is in a solution. Measured in g/dm3.
to make cm3 into dm3, just divide by 1000.