- Created by: stesar
- Created on: 23-11-17 22:12
The Electrochemical Series
(top) Li ... Al ... Cl (bottom)
More reactive (top) - forms from atom to ion easily
Less reactive (bottom) - doesn't form ions easily - tend to stay as atoms
Elements/ the ionic substance must be molten or dissolved.
Na -> Na+ + e-
E.g. 1) Sodium Chloride
Positively charged ions move to the negative electrode and reduced to make Sodium atoms.
Negatively charged ions move to the positive electrode and are oxidised to make Chlorine atoms.
Break up of hydrogen ions and hydroxide ions. H20 -> H+ + OH- = four types of ions present: 2 for ionic compound, 2 for the water.
Electrolysis of Sodium Chloride (aq)
Anode - Chloride - swimming pools
Cathode - Hydrogen - margarine
In solution - sodium hydroxide - soap
A base is an oxide or hydroxide of a metal e.g. Calcium Oxide (aq) - alkali
If the base is soluted (dissolves in water) then it would be called on alkali e.g. Calcium oxide (aq) - alkali
The chemical reaction between an acid and an alkali/ base is called neutralisation; a salt is formed
Example: hydrochloric acid + Calcium Oxide -> calcium chloride + water
NITRIC ACID - NITRATE
SULPHURIC ACID - SULFATE
HYDROCHLORIC ACID - CHLORIDE
Aluminium Oxide - An Amphoteric Substance
If an acid is present, it will act as a base e.g. Aluminium oxide reacts with HOT hydrochloric acid to make aluminium chloride + water (neutralised)
If a hot base is present, it will act as an acid.
Aluminium oxide is a chemically inert (doesn't react) except under certain conditions e.g. when a hot acid or base is present. This means it has a lot of uses:
If they dissolve in water, they form metal hydroxide (aq) which are alkalis.
Amphoteric - Substance that can act both as an acid or a base
Alkali - A base that dissolves in water to form hydroxide ions, OH-
Acid - A compound containing hydrogen that dissociates in water to form hydrogen ions
Base - A compound that reacts with an acid to form a salt and water
Hydrochloric Acid -> Sodium Hydroxide -> Sodium Chloride
Sulfuric Acid -> Magnesium -> Magnesium Sulfate
Nitric Acid -> Calcium -> Calcium Nitrate
Sulfuric Acid -> Zinc -> Zinc Sulfate
Hydrochloric Acid -> Iron Oxide -> Iron Chloride
- d block of elements
- when they react, they lose electrons to form positive ions
- They lose 4s electrons before they lose 3d electrons
- They form ions with more than 1 oxidisation state
- Can form complex ions
- They form coloured compounds
In a solution, transition metals compound from complex ions.
A complex ion consists of a central transition metal ion bonded to ligand
A ligand is a molecule or ion that donates a lone pair of electrons to form a dative covalent bond/ attraction.
- Why transition metals are able to easily form complex ions:
- Ligand uses a lone pair of electrons
- Forms a dative-covalent bond
- Transition metals use their 3d and 4s orbitals to bond so can accept the lone pair of electrons
Uses of Transition Metals
- Platinum + rhodium are used in the catalyst converters
- Iron is the catalyst in the Haber Process - it lowers the activation energy. This lowers the const and helps the environment.
- Ammonia is used in fertilisers
The Contact Process
Vandium (v) oxide is used as a catalyst to make sulfuric acid in the contact process.
- Stage 1: Sulfur dioxide is made
The sulphur dioxide is mixed with excess air
- Stage 2: sulphur trioxide is made
- Stage 3: Sulfur trioxide is converted into sulfuric acid
Sulfur trioxide is dissolved in concentrated sulfuric acid
The Role of Vandium Oxide
can be used as a catalyst since it can change its oxidisation state
As sulphur dioxide is oxidised to sulphur trioxide, the vandium oxide is reduced
The vandium oxide is then oxidised with oxygen - means it can be used again
Aluminia and Aluminium Extraction
Aluminia is a form of aluminium oxide found in the mineral bauxite. It is extracted and purified using the Bayer Process. The stages of the process are:
- Crush the Bauxite
- React with NaOH (aq) at 170degrees
- Filter out solid impurities
- Allow the crystalise to form Al(OH)3
- Heat in rotary kiln to form Al2O3
Most of the aluminia separated in this way is used in the Hall-Heroult Process to form the aluminium by electrolysis.
Some are used in the refractory material in kilns.There are materials that retain their strength and are chemically stable at high temperatures.
Aluminium ore, bauxite is mined and then processed to form alumina, which is aluminium oxide. Molten alumina is then electrolysed using the Hall-Heroult process.
Cryolite is added to the alumina to lower the melting point and save energy. The lining of the steel tanks is made from carbon, which acts as the negative electrode. Here, aluminium ions are reduced to form molten aluminium
Al3+ + 3e- -> Al
The molten aluminium can then be drained off and cast into ingots. The positive electrodes are made of carbon. Here, oxide ions are oxidised to form oxygen gas.
2O2- -> O2 + 4e-
The carbon electrodes have to be replaced regularly as they react with the oxygen as it forms.
The main titanium is rutile, which contains titanium dioxide, TiO2. Although titanium has a very similar reactivity to aluminium, it is not generally extracted by electrolysis as the titanium formed often has 'tree-like' crystals, which can affect the electrodes. Also, side-reactions with titanium ions at both electrodes can lead to impurities.
Most titanium is extracted using the Kroll Process
1) Titanium dioxide, coke and chlorine are heated together at about 900degrees, to form titanium chloride
2) Magnesium is used as a reducing agent to form Titanium
The process is expensive due to the large amounts of energy needed to create the very high temperatures involved. Also, the magnesium used in step 2 is produced by an energy-intensive electrolysis process. The process is time-consuming as it's a batch process.
Carboxylic Acid - COOH - ...oic acid
Ester - COO - ...oate
Aldehyde - CHO - ...al
Ketone - C-CO-C - ...one
Alcohol - OH - hydroxy... - ...ol
Alkene - C=C - ...ene
Alkane - C-C - ...ane
Haloalkane - F, -Cl, -Br, -l - Flouro, chloro, bromo, iodo
Alkyl - CH3 - methyl
Organic compounds are all carbon-based compounds. There are different families of organic compounds, they are called alkenes, alkanes and alcohols = homologous series
They can be classed as aliphatic (straight or branched chains), alicyclic (Ring Structure) or aromatic (contains a benzene ring)
Alkenes - hydrogen + carbon = hydrocarbon
They are said to be saturated, single bonds only.
Pentane - 5 carbons
Hexane - 6 carbons
Heptane - 7 carbons
Octane - 8 carbons
Nonane - 9 carbons
Decane - 10 carbons
They are unsaturated, have a double bond. This means they can react with something else.
General Formula - C n H 2 n
Naming organic compounds
The stem is the main part of the name an comes from the longest c-chain
The prefix is the front part of the name and identifies functional groups.
The suffix is the end of the name e.g. 'ene' or 'ane'
Isomer - same atom but different structure
- Chain isomer
- Positional isomer - same c chain and functional groups, but the functional groups are on different C's
- Functional isomer - have different functional groups e.g. C3H6O
Propanone - acetone
Stereoisomer - have the same general formula, but a different arrangement of atoms - different properties, always have a double or triple bond so atoms can rotate.
Sigma Bonds - 4 electrons in its outer shell, forms 4-C-H covalent bonds. The electron clouds from each bond overlap.
Reaction Mechanisms - step-by-step sequence showing the movement of e's in a process
Halogenation - addition of halogen to an alkane
Homolytic Fission - formation of a free radical by splitting a bond so each free radical has 2 electron
Free Radical - atom with a single unpaired electron
Propagation and Termination
Propagation - free radicals hit ethane molecule, making longer free radicals. They use ore of the electrons in the double bond to form a new bond between itself and carbon. Other electrons return to the carbon atom.
Termination - 2 free radicals collide to produce the final molecule (polythene) made up of many different length chains.
Lots of long-chain alkanes = don't need them and want to break them up to make shorter chain alkanes as they're in high demand.
Long-chain molecules are cracked into shorter chains by thermal decomposition (heat)
e.g. octane = hexane +ethane -> make plastics
Alkanes and combustion
Alkanes are often used as fuel as complete combustion releases large amounts of energy.
Complete Combustion - where there's plenty of oxygen
Incomplete Combustion - not enough combustion
Effects of Temperature on Cracking
Higher the temp = shorter the alkene chain made
High temp = long chain molecules break near ends
Is the thermal energy stored in a chemical system
H = U + pV
Diaphragm V Cell Membrane
The chlorine can react with the sodium hydroxide solution, forming sodium hypochlorite (bleach). To prevent this:
A membrane with a mixture of asbestos and polymers. Higher level of liquid on anode so NaOH doesn't flow back and mix with chlorine
Membrane from a polymer so only positive ions can get through Cl- can't get through to react with NaOH