organic chemistry - C10 + C11

chemical test for the presence of water - cobalt (II) chloride

• done with cobalt chloride paper

• in the presence of water the paper turns from blue to pink

• (Anhydrous cobalt(II) chloride, CoCl2, is blue

  Hydrated cobalt(II) chloride, CoCl2•6H2O is pink)

• reversible

chemical test for the presence of water - copper(II) sulfate

• in the presence of water copper(II) sulfate turns from white to blue

• reversible

how to test for the purity of water

• Impurities tend to increase the boiling point of water → impure water boils at temperatures above 100 oC

• Impurities tend to decrease the melting point of water → impure water melts at temperatures below 0 oC

distilled water use

used in practical chemistry rather than tap water because it contains fewer chemical impurities

treatment of the water supply - stage 1

• sedimentation -

  • Water is pumped into sedimentation tanks and allowed to stand for a few hours

  • Mud, sand and other particles will fall to the bottom of the tank due to gravity and form a layer of sediment

  • The water is then filtered through sand and gravel to remove smaller particles

treatment of the water supply - stage 2

• filtration - treatment with carbon(charcoal)

• removes unpleasant tastes + odors

treatment of water supply - stage 3

• chlorination

• Bacteria and other microorganisms are too small to be trapped by the filters

• chlorine is added to the water supply to kill bacteria and other microorganisms (pathogens)

• e.g Cholera and typhoid →bacterial diseases that come from untreated water

composition of air

• 78% nitrogen (N2)

• 21% oxygen (O2)

• 1% - noble gases and carbon dioxide

sources of carbon dioxide and carbon monoxide + particulates

• carbon dioxide - complete combustion of carbon-containing fuels

• carbon monoxide + particulates - incomplete combustion of carbon-containing fuels

sources of methane

• decomposition of vegetation

• waste gases from digestion in animals

sources of oxides of nitrogen and sulfur dioxide

• oxides of nitrogen - car engines

• sulfur dioxide - combustion of fossil fuels which contain sulfur compounds

effects of carbon dioxide and carbon monoxide

• carbon dioxide - increased global warming → climate change

• carbon monoxide - toxic gas

effects of particulates and methane

• Particulates - increased risk of respiratory problems

• Methane - increased global warming → climate change

Effects of oxides of nitrogen and sulfur dioxide

• oxides of nitrogen - acid rain + respiratory problems

• Sulfur dioxide - acid rain

How to reduce carbon dioxide emissions

• hydrogen and renewable energy supplies (e.g solar or wind energy)

• more fuel-efficient vehicles, (e.g. electric and hybrid cars)

• Reducing the number of vehicles on the road ( e.g. public transport)

• Recycling or reusing products made from crude oil

• Reducing household energy consumption ( e.g. turning lights out, using more efficient appliances)

• Reducing deforestation and / or re-forestation

  • Planting more trees, can help reduce the amount of atmospheric carbon dioxide through photosynthesis

How to reduce methane emissions

• Reduce the amount of livestock farming

  • (Methane is produced during digestion in animals)

How to reduce acid rain

• Acid rain is caused by oxides of nitrogen and sulfur dioxide 

• Catalytic convertors in vehicles can be used to remove oxides of nitrogen

How to reduce sulfur dioxide emissions

• Using fuels which contain low levels of sulfur

• Flue gas desulfurization

  • main way to reduce sulfur dioxide emissions

  • Waste gases from coal fired power stations are passed into a scrubbing chamber

  • They are sprayed with a wet slurry of calcium oxide and calcium carbonate 

  • The calcium compounds react with sulfur dioxide to produce calcium sulfate

How do carbondioxide and methane cause global warming

• Green house effect

  • some thermal energy is absorbed by greenhouse gases(e.g carbon dioxide and methane) and is re-emitted in all directions

  • This reduces the thermal energy lost into space and traps it within the Earth’s atmosphere, keeping the Earth warm

How do oxides of nitrogen form in car engines

nitrogen and oxygen react in the high pressure and temperature conditions of internal combustion engines and blast furnaces

How to catalytic converters work ?

• 2CO + 2NO → 2CO2 + N2

• contain a series of transition metal catalysts in a honeycomb shape + converter to increase the surface area for reaction

• A series of redox reactions occurs which neutralizes the greenhouse gases

Saturated vs unsaturated compound

• saturated - molecules in which all carbon-carbon bonds are single bonds

• Unsaturated - molecules in which one or more carbon-carbon bonds are not single bonds

Homologous series definition

A family of similar compounds with similar chemical properties

General characteristics of a homologous series

• have the same general formula

• Display a trend in physical properties

Fossil fuels

Coal, natural gas, petroleum

Describe methane, hydrocarbons,petroleum

• methane - the main constituent of natural gas

• Hydrocarbons - compounds that contains hydrogen and carbon only

• Petroleum/crude oil - a mixture of hydrocarbons, not useful by itself as a mixture

Why does fractional distillation of crude oil work?

• The molecules in each fraction have similar properties and boiling points, which depend on the number of carbon atoms in the chain

• size of molecule is directly related to how many carbon and hydrogen atoms the molecule contains

The separation of petroleum by fractional distillation

• Carried out in a fractionating column - very hot at bottom and cooler at the top - temperature gradient

• crude oil is heated → vaporizes

• vapors of hydrocarbons enter column

• Vapors of hydrocarbons with high boiling points condense at the bottom of the column

• Vapors of hydrocarbons with lower boiling points rise up the column and condense at the top 

Uses of fractions - refinery gas fraction + gasoline/petrol fraction

• refinery gas - used in heating + cooking

• Gasoline/petrol - for fuels used in cars

Uses of fractions - naphtha fraction + diesel/gas oil fraction + bitumen

• naphtha - chemical feedstock

• Diesel/gas oil - fuel used in diesel engines

• Bitumen - making roads

Alkanes

• saturated hydrocarbons - single covalent bonds only

• Properties

  • un reactive except for combustion reactions

Bonding in Alkenes

• Includes a double carbon-carbon covalent bond

• Unsaturated hydrocarbons

How to tell the difference between alkanes and alkenes experiment

• See their reaction with aqueous bromine

• Alkane - no change to bromine water

• Alkene - will cause bromine water to become discolored

Alkene + Alkane + alcohol general formula

• Alkene - CnH2n

• Alkane -CnH2n+2

• alcohol - CnH2n+1OH

Manufacturing of alkenes and hydrogen - cracking

• Cracking involves heating the hydrocarbon molecules to around 600 – 700°C to vaporise them

• vapors pass over a hot powdered catalyst of alumina or silica

• Vapors come in contact with catalyst → breaks covalent bonds into molecules → thermal decomposition reactions

• produces an alkene + another hydrocarbon

Addition reaction - alkene + bromine

• ethene + bromine → dibromoethane

• C2H4 + Br2 → C2H4Br2

• decolorises bromine

Addition reaction - alkene + hydrogen

• make an alkane

• e.g ethene + H2 → ethane, propene + H2 → propane (has to be in presence in nickel catalyst)

Addition reactions - alkene + steam

• make an alcohol

• requires acid catalyst

• e.g ethene + steam → ethanol

combustion of ethanol

• produces carbon dioxide and water

• this is because it burns excess oxygen

• C2H5OH (l) + 3O2 (g) → 2CO2 (g) + 3H2O (l)

Ethanol, Methanol and Propanol formula

• ethanol - C2H5OH

• methanol - CH3OH

• propanol - C3H7OH

ethanol uses

• solvent

• fuel in cars

polymers definition

large molecules built up from many smaller molecules called monomers

formation of polyethene

addition polymerisation using ethene monomers

addition polymerisation

• joining same alkene monomers

• double bond breaks

• polymer formed → only single bonds

• forms only polymer

condensation polymerisation

• 2 different monomers linked together with the removal of a small molecule (usually H2O)

• forms polymer + 1 water molecule per linkage

forming Nylon

• a polyamide is formed from a dicarboxylic acid and a diamine

• condensation polymerisation

polymer vs polyester

• polyester - condensation polymer, biodegradable

• polymer - addition polymer, not biodegradable