Chem Paper 2 - Final Exams - Coggle Diagram
Chem Paper 2 - Final Exams
L1 - Rates of Reaction
Rate of reaction describes how quickly reactants turn into products. Activation energy is the minimum amount of energy needed for a chemical reaction to take place.
When the volume of gas produced / volume of gas lost is constant, the reaction has completed.
L2 - Factors Affecting Rate of Reaction
Surface area: Larger surface area results in an increased collision frequency as there is a greater surface on which particles can collide.
Temperature: A higher temperature results in a greater average kinetic energy. This means that particles are more likely to have the necessary activation energy to cause a successful collision to occur. This increases the the frequency of successful collisions.
Concentration: More reactant particles per unit volume so the frequency of successful collisions increases.
Catalysts offer a lower energy pathway for the reactants to take (lowers activation energy) so that more reactant particles have the needed activation energy and so the frequency of successful collisions increases. These catalysts remain chemically unchanged.
L3 - RoR (Cross)
Rate = 1 / Mean Time
Add a fixed volume of sodium thiosulphate to a conical flask.
Place this flask on a white tile with a cross on it.
Measure a fixed volume and concentration of acid using a measuring cylinder.
Add the acid to a conical flask, begin a timer and stop when the cross is no longer visible.
When reacting sodium thiosulphate with acid, a sulphur precipitate is formed.
L4 - RoR (Cylinder)
Upturned measuring cylinder submerged in water.
Feed a pipe into a cylinder attached to a bung.
Mg ribbon of fixed length added to flask.
Add HCL, bunch and record at time intervals.
L5 - Equilibrium Shifting
A reaction is reversible if it can occur both forwards and backwards. If the system is in a closed system, it can be said to be in equilibrium.
Dynamic equilibrium is a state in which the direction of equilibrium is constantly changing. The rates of the forwards and backwards reaction are the same.
If the pressure is increased, the equilibrium will shift to produce more of the species with the fewer number of moles.
If the surroundings are heated, the equilibrium will shift to oppose the change (cool the system) and so will perform the endothermic reaction more frequently.
L1 - Alkanes and Crude Oil
Alkanes = Saturated due to single bonds.
Crude oil is the remains of ancient biomass (mainly plankton) that has been buried in mud.
L2 - F-Distillation
The fractions obtained from FD can be used to produce feedstocks and materials for the petrochemical industry.
Shorter chain hydrocarbons will vaporise first as they contain weaker intermolecular forces between covalently bonded molecules; they rise further up the distillation column and then cool and exit the column.
Shorter-chain hydrocarbons burn better in the presence of oxygen and so make better fuels.
Example fractions: Naphtha, bitumen, petrol, diesel oil, heavy fuel oil and kerosene.
Materials produced by the petrochemical industry include: solvents, lubricants, polymers and detergents.
L3 - Properties of Hydrocarbons
The longer a hydrocarbon's chain, the more viscous it is, the less flammable it is, the less volatile and the higher the boiling point.
L4 - Alkenes and Cracking
Alkenes are capable of turning bromine water colourless while alkanes are not.
Steam or catalytic cracking converts longer chain alkanes into shorter chain alkanes and an alkene.
[Bromination] - Room temp and pressure.
[Hydration] - 300 degrees, 60 atmospheres of pressure with a silica catalyst.
[Hydrogenation] - Room temp, pressure and a platinum catalyst.
Alkenes are unsaturated hydrocarbons.
Alkenes are more reactive than alkanes and can be used to produce polymers.
L5 - Alcohols
Alcohols are often used as fuels, solvents and in alcoholic drinks (ethanol). Aqueous ethanol is produced through fermentation (anaerobic respiration of yeast at 30 degrees).
Alcohols are soluble in water and form neutral solutions. Alcohols may react with sodium to produce sodium ___oxide.
Alcohols react with an oxidising agent to produce a carboxylic acid and water.
L6 - Carboxylic Acids
In water, carboxylic acids are weak (they do not fully ionise). This reaction is reversible. These acids may react with alcohols to produce esters (which have a pleasant smell) and water.
Esterification requires a sulphuric acid catalyst and is reversible.
L7 - Polymerisation
One type of alkene monomer is used for this. No other molecules are formed in the reaction.
Condensation often uses a dicarboxylic acid, diol or diamine reacting to form an ester and water.
L8 - Natural Polymers
Glycine is an amino acid. It has an amine group and a carboxylic acid group so can form condensation polymers by itself (polypeptides).
Combining different amino acids to form a polymer deems the chain a protein.
DNA consists of two polymer chains made up from nucleotide monomers. Other natural polymers include proteins (amino acids), start (glucose) and cellulose (glucose).
L1 - Purity and Formulations
Pure substances will melt and boil at specific, fixed temperatures, not over a range of temperatures.
A formulation is a complex mixture that has been designed as a useful product. Examples include medicines, alloys, paints, fuels and fertilisers.
L2 - Chromatography
The chemicals in a mixture may separate into different 'spots' depending on the solvent used.
Capillary tube used to add spots. Rf is used to identify the specific chemicals that a mixture contains. It is calculated with Mixture Distance / Solvent Distance.
Should repeat with a different solvent to narrow down search.
L3 - Testing for Ions
Li[+]: Crimson Red
Al[2+]: White (Redissolves)
Effervescence and turns limewater cloudy when bubbled through.
Dilute nitric acid added.
Dilute silver nitrate added.
White precipitate forms.
L4 - Spectroscopy
The intensity of the lines on a line spectrum indicate the concentration of the substance in a sample.
Benefits of instrumental methods:
Large amounts of CO2.
Little or no oxygen.
Volcanic activity released nitrogen and water vapour.
Oxides of nitrogen are produced within the high temp and pressures of car engines.
L1 - Potable Water
Drinking water must have sufficiently low levels of dissolved salts and cannot have a high number of microbes / bacteria.
Passed through water beds to remove leaves and suspended particles.
Microbes killed through sterilisation (using UV or chlorine).
Sea water (desalination):
Distillation or reverse osmosis.
L2 - Waste Water
Screened after passing through mesh (removes grit / solids).
Sewage settles in large sedimentation tank to produce semi-solid sludge and liquid effluent.
Sludge is taken away and digested by anaerobic bacteria (producing biogas).
Air is bubbled through liquid effluent (allowing aerobic bacteria to multiply).
Phytomining: Plants grown, absorb metal and then burned (ash used).
Bioleaching: Bacteria mixed with ore, bacteria produces a leachate.
Scrap iron used for displacement.
L3 - Corrosion
For rusting to occur, water and air must be present. It can be prevented through galvanisation (sacrificial protection) / electroplating.
L4 - NPK and Haber
SEE EXTENSION MIND MAP
N2 + 3H2 <--> 2NH3 (Iron catalyst, 450, 200 atm)