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docbreactiontypes updated Feb 6th 2008 |
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OXIDATION - definition and examples |
REDUCTION - definition and examples |
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The gain or addition of oxygen by an atom, molecule or ion
e.g. ...
(1) S + O2 ==> SO2 [burning sulphur - oxidised to sulphur dioxide] (2) CH4 + O2 ==> CO2 + 2H2O [burning methane to water and carbon dioxide, methane oxidised as the C and H atoms gain O] (3) 2NO + O2 ==> 2NO2 [nitrogen monoxide is oxidised to nitrogen dioxide by gaining oxygen] (4) SO32- + [O] ==> SO42- [oxidising the sulphite ion to the sulphate ion] |
The loss or removal of oxygen from a compound etc.
e.g.
...
(1) CuO + H2 ==> Cu + H2O [loss of oxygen from copper(II) oxide shows it to be reduced to copper atoms] (2) Fe2O3 + 3CO ==> Fe + 3CO2 [iron(III) oxide ore is reduced to iron metal by oxygen loss in the blast furnace] (3) 2CO + 2NO ==> CO2 + N2 [nitrogen monoxide reduced to nitrogen by losing oxygen] (4) CuO + Mg ==> Cu + MgO [loss of oxygen from copper(II) oxide shows it to be reduced to copper atoms] |
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The loss or removal of electrons from an atom, ion or molecule
e.g.
(1) Fe ==> Fe2+ + 2e- [iron atom loses 2 electrons to form the iron(II) ion] (2) Fe2+ ==> Fe3+ + e- [the iron(II) ion loses 1 electron to form the iron(III) ion] (3) 2Cl- ==> Cl2 + 2e- [the loss of electrons by chloride ions to form chlorine molecules in electrolysis of chlorides or halogen displace] |
The gain or addition of electrons by an atom, ion or molecule e.g. ...
(1) Cu2+ + 2e- ==> Cu [the copper(II) ion gains 2 electrons to form neutral copper atoms e.g. in electrolysis or metal displacement reactions) (2) Fe3+ + e- ==> Fe2+ [the iron(III) ion gains an electron and is reduced to the iron(II) ion] (3) 2H+ + 2e- ==> H2 [hydrogen ions gain electrons to form neutral hydrogen molecules] (4) Cl2 + 2e- ==> 2Cl- [chlorine molecules gain electrons to form chloride ions |
| An oxidising agent is the species that gives the oxygen or removes the electrons | A reducing agent is the species that removes the oxygen or acts as the electron donor |
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Redox reaction analysis based on the oxygen definitions |
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Redox reaction analysis based on the electron definitions |
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(1) Addition polymers are formed by (e.g. alkene) monomers adding together and forming no other products except the polymer e.g. ethene ==> poly(ethene), phenylethene ==> poly(phenylethene), old name polystyrene. |
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(2) Condensation polymers are formed by one or more monomers add together, forming the polymer BUT in forming the polymer small molecules are eliminated 'between' the monomers e.g. dicarboxylic acid + diol ==> polyester + water, diamine + dicarboxylic acid ==> nylon + water |
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(Ex. 1a) formation of poly(ethene) or 'polythene' from polymerising ethene to form an addition polymer. No other molecule is formed - just simple addition polymerisation. |
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(Ex. 1b) formation of poly(chloroethene) or 'PVC' from polymerizing chloroethene to form an addition polymer. No other molecule is formed - just simple addition polymerization. |
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+ small molecules eliminated In the case of Nylon, for each 'red' monomer - 'blue' monomer, a link is formed at each end of each monomer molecule by eliminating a water molecule e.g. where [R] = 'rest of molecule' a single link formation reaction can be shown as [R]-COOH + HO-[R] ==> [R]-CO-O-[R] + H2O |
(Example of 2) representation of a Nylon
made from two different monomers (shown as red and green + linking
atoms)
joining by eliminating a small molecule between the two monomers,
therefore Nylon is a
condensation
polymer. |
| NEUTRALISATION |
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Two examples of reversible reactions are given below: (more details for GCSE) (a) The thermal decomposition of ammonium chloride. On heating strongly, the white solid ammonium chloride, decomposes into a mixture of two colourless gases - ammonia and hydrogen chloride. On cooling the reaction is reversed and solid ammonium chloride reforms. Ammonium chloride
+
heat
NH4Cl(s) (b) The thermal decomposition of hydrated copper(II) sulphate.
blue hydrated copper(II)
sulphate + heat
CuSO4.5H2O(s)
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(a) The formation of calcium oxide (lime) from calcium carbonate (limestone) calcium carbonate
(limestone) CaCO3(s) (b) The formation of ammonia nitrogen + hydrogen |
| Hydration and dehydration (often reversible under the right conditions) |
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Metal displacements |
Non-metal displacements |
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This means to coat iron or steel with a layer of zinc to stop it rusting (more details on Metal Reactivity page) |
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| The synthesis of ammonia by combining nitrogen and hydrogen using high temperature, pressure and an iron catalyst. (all the details) | |
| Contact Process |
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| Double decomposition |
Double decomposition
is chemical
reaction that takes place between two compounds, in which the first part
of one compound combines with the second part of another compound. The
bits left over combine to form the second compound. One of the compounds
is usually insoluble.
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| Catalytic Conversion (car exhaust) |
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| Esterification |
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| Rusting |
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| Substitution |
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| Addition |
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(overlapping terms, physical changes rather than chemical changes) |
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Deliquescent |
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Hygroscopic |
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ks4 science examinations gcse-igcse chemistry
revision *
ks4 science examinations-gcse-igcse chemistry revision * ks4 science
examinations-gcse-igcse chemistry revision * ks4 science examinations-gcse-igcse chemistry
revision * ks4 science examinations-gcse-igcse
chemistry revision * ks4 science examinations-gcse-igcse chemistry revision * SITE PURPOSE EDUCATION - online learning
or 'self-private-tuition' using revision notes, quizzes,
practice tests involving GCSE Science CHEMISTRY in the areas of REVISING
only the CHEMISTRY-Earth Science-Radioactivity at Doc Brown's
Chemistry Clinic via HOMEPAGE in secondary school/schools, 6th form college/colleges,
academy/academies or home self-study. Hopefully it will encourage
interest and understanding of Chemistry, Earth Science and Radioactivity
in any country of the world, though the site is written entirely in English. The website is designed to help
and unofficially support students/teachers revise-learn/teach the chemistry for modular
or co-ordinated examination science
courses from UK QCA based AQA, OCR (Oxford and Cambridge) Twenty First (21st) Century and Gateway Science, Edexcel
360Science ,
Nuffield, Salters, Cambridge International (CIE), London International, WJEC, CCEA
exams etc.
Also, national award assessments-examinations for GCSE-IGCSE-KS4-O
level-BTEC-NVQ
applied, additional and chemistry national science courses. Also covers,
mainly via quizzes the UK National KS3 SATs Science-biology/chemistry/physics (SAT revision levels 3-5
or 5-7) and covers much of the revising, learning and teaching chemistry
examinations for the
national curriculum for secondary schools and colleges. The site does
not support the content of England, Wales or Northern Ireland primary
science KS1 or KS2. The notes should also provide some background theory
for a coursework assignment or project. BUT please note that
my on-line revision notes and quizzes are no substitute for good classroom
teaching-lecturing and thorough studying of your own notes and textbooks, practicing past papers
and a copy of the syllabus which are readily downloaded from the
examination board sites, but I hope here and there they will lend a
tutoring hand on some topic, unit, module etc. For final revision you
have to be intellectually honest about what you don't know or follow, YOU have to
take the stuff to pieces, analyse what you do/do not understand
and reconstruct it so it all makes sense in the end. There is no other
way, there are no magic secrets on how to revise and learn, its mainly
down to hard work and just good old fashioned study and employing teach-yourself
strategies without the need for extra tutors and tutoring lessons. I also think
there is too much hit and miss revision using past papers (which I do NOT
supply) and not enough
systematic revision. I also hope it will help teachers in planning
lessons and developing schemes of work for science-chemistry. There are no
lesson plans on the site but there are plenty of quizzes to incorporate into
classroom activities whether photocopied or on electronic whiteboard projector
for use as self-tuition-assessment purposes and a variety of teaching and
learning styles and the images may be used in Microsoft Word documents and powerpoint projections.
The site seems to be used by a large number of home study tutors, particularly
the revision notes. An individual tutor may print out the notes for
science-chemistry learning teaching-tuition purposes and for background material
for assignments and projects. I have no interest or time in producing WORD.doc or xxxx.pdf files
of the notes at the moment. Neither have I time to write up many practical
laboratory experiments ('lab'-'labs') at the moment, but the notes contain lots
of background information of chemical reactions in terms of
observations-balanced equations-reactants-products-theory etc. I also find it
difficult to recommend specific exam websites or syllabus textbooks, it depends exactly on
what you need, what you have time for, and there are so many of them to choose
from and I do not supply past examination papers for classes. The sites
resources include revision notes, quizzes and worksheets which provide support
for home study or tuition for homework and coursework help e.g. science
investigations for any of the key stage courses indicated, but I do not supply
lesson plans. Dr W P Brown gcse
10-11-2007 * ks4 science examinations gcse-igcse chemistry
revision *
ks4 science examinations-gcse-igcse chemistry revision * ks4 science
examinations-gcse-igcse chemistry revision * ks4 science examinations-gcse-igcse chemistry
revision * ks4 science examinations-gcse-igcse
chemistry revision * ks4 science examinations-gcse-igcse chemistry
revision
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docbreactiontypes updated Feb 6th 2008 |