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4_73calcs07mam updated April 9th 2008 |
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On-line chemistry CALCULATIONS for KS4 Science, GCSE Chemistry and AS Chemistry (basic calculations) EMAIL query?comment or request for type of GCSE calculation? |
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The mole is most simply expressed as the 'formula mass in g' of the defined chemical 'species', and that is how it is used in most chemical calculations. Every mole of any substance contains the same number of the defined species. The actual particle number is known and is called the Avogadro Constant and is equal to 6.023 x 1023 'defined species' per mole. This means there are that many atoms in 12g of carbon (C = 12) or that many molecules of water in 18g* (H2O = 1+1+16 = 18, H = 1; O = 16) * this is about 18cm3, so picture this number of molecules in a nearly full 20cm3 measuring cylinder or a 100ml beaker less than 1/5th full! However, the real importance of the mole is that it allows you to compare ratios of the relative amounts of reactants and products, or the element composition of a compound, at the atomic and molecular level. If you have a mole ratio for A:B of 1:3, it means 1 particle of A to 3 particles of B irrespective of the atomic or formula masses of A and B. (see also section 6. for reacting masses not using moles) Important Note. Relative is just a number based on the carbon-12 relative atomic mass scale. Molar mass is a term used to descsribe the mass of one mole i.e. the relative atomic/formula/molecular mass in grams (g). Examples:
For calculation purposes learn the following formula for 'Z' and use a triangle if necessary.
Using the Avogadro Constant, you can actually calculate the number of particles in known quantity of material.
More advanced use of the mole and Avogadro Number concepts (for advanced level students only)
In terms of electric charge, 1 Faraday = 96500 C (coulombs) = 6 x 1023 electrons If you have 2.5 moles of the ionic aluminium oxide (Al2O3) you have ...
When you write ANY balanced chemical equation, the balancing numbers, including the un-written 1, are the reacting molar ratio of reactants and products. Extra Advanced Questions - more suitable for Advanced AS-A2 students which can be completely tackled after ALSO studying section 9 on the molar volume of gases and ANSWERS to QA7.1 QA7.1 This question involves using the mole concept and the Avogadro Constant in a variety of situations. The Avogadro Constant = 6.02 x 1023 mol-1. The molar volume for gases is 24dm3 at 298K/101.3kPa. Atomic masses: Al = 27, O = 16, H = 1, Cl = 35.5, Ne = 20, Na = 23, Mg = 24.3, C = 12 Where appropriate assume the temperature is 298K and the pressure 101.3kPa. Calculate .... (a) how many oxide ions in 2g of aluminium oxide? (b) how many molecules in 3g of hydrogen? (c) how many molecules in 1.2 cm3 of oxygen? (d) how many molecules of chlorine in 3g? (e) how many individual particles in 10g of neon? (f) the volume of hydrogen formed when 0.2g of sodium reacts with water. (g) the volume of hydrogen formed when 2g of magnesium reacts with excess acid. (h) the volume of carbon dioxide formed when the following react with excess acid (1) 0.76g of sodium carbonate and (2) 0.76g sodium hydrogencarbonate (i) the volume of hydrogen formed when excess zinc is added to 50 cm3 of hydrochloric acid, concentration 0.2 mol dm-3. (j) the volume of carbon dioxide formed when excess calcium carbonate is added to 75 cm3 of 0.05 mol dm-3 hydrochloric acid. Self-assessment Quizzes for GCSE or AS(basic) [mam] Type in answer
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These chemical calculations pages of revision notes will also prove useful for basic revision for students studying revising tutoring teaching Advanced Level GCE AS A2 IB CHEMISTRY courses in unofficial support the Chemistry in any advanced-subsidiary AQA, EDEXCEL, Nuffield, Salters, OCR, CIE, WJEC, SQA and CCEA (NI) UK or Cambridge/London/Edexcel International and OCR/CIE International examinations.
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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4_73calcs07mam updated April 9th 2008 |