4. INORGANIC Qualitative TESTS for gases and non-metallic elements

For diagram of a possible procedure see test for carbonate

If excess carbon dioxide bubbled through you form a clear colourless solution of calcium hydrogencarbonate.

CaCO_3(s) + H₂O_(l) + CO_2(aq) ==> Ca(HCO₃)_2(aq)

The relighted splint is mainly combustible carbon.

(ii) Apply a drop of silver nitrate on the end of a glass rod

(ii) A white precipitate.

(ii) In water forms chloride ions - hence precipitate with silver nitrate, see chloride test.

is reduced to the green Cr³⁺_(aq) ion.

Ammonia gas NH₃

Strong pungent odour.*

(i) Damp red litmus.

(ii) Near fumes of conc. hydrochloric acid.

(ii) Gives white clouds with HCl fumes.

(ii) It forms fine ammonium chloride crystals with HCl. (*volatile organic aliphatic amines give the same result, and smell more fishy)

Bromine Br_{2 (l or aq)}

A dark red liquid - orange-brown fumes, yellow-orange aqueous solution. The other common orange-brown gas is nitrogen dioxide

(ii) Mix with silver nitrate solution.

(ii) Cream ppt. of silver bromide. See bromide test.

>C=C< + Br₂ ==> >CBr-CBr<

(ii) Ag⁺_(aq) + Br^-_(aq) ==> AgBr_(s) 

 Any soluble bromide gives a silver bromide precipitate.

Chlorine gas Cl₂

A pungent green gas.

Test (ii) on its own is no good, could be HCl.

(ii) A drop silver nitrate on the end of a glass rod into the gas.

(ii) White precipitate.

(ii) It forms a small amount of chloride ion in water, so gives a positive result for the chloride test.

Iodine (i) solid or (ii) solution

A dark coloured solid.

(ii) Test aqueous solution or solid with starch solution.

(ii) A blue black colour.

(ii) Forms a blue-black complex with starch and in biology the test is used to detect starch with iodine solution.

Pb²⁺_(aq) + S^2-_(aq) => PbS_(s) 

The gas is formed when acids react with sulphides.

Easy to get these colour changes muddled!

(ii) Dip in dry blue cobalt chloride paper.

(ii) Turns from blue to  pink.

(ii) Pink hydrated cobalt ion formed [Co(H₂O)₆]²⁺

KS3 SCIENCE * KS4 SCIENCE GCSE IGCSE GCE AS A2 IB CHEMISTRY * SITE PURPOSE EDUCATION - online learning or 'self-private-tuition' using revision notes, quizzes, practice tests involving SCIENCE 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 and may help with 1st year undergraduate university chemistry courses. 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 science courses and examinations, Advanced Subsidiary Level GCE-AS-A2-IB-KS5-BTEC-NVQ National Chemistry assessment levels, KS3 SATs Science-biology/chemistry/physics (SAT revision levels 3-5 or 5-7) and covers much of the revising, learning and teaching chemistry of the International Baccalaureate, K12 US grade 6,7,8,9,10,11,12,AP basic level examinations courses 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 a 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 printout 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 revision notes 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 I 29-11-2007 * KS3 SCIENCE * KS4 SCIENCE GCSE IGCSE GCE AS A2 IB CHEMISTRY

Online free help resources for Key Stages 3 SATs (S.A.T.s), 4 & 5AQA, Edexcel, OCR, CIE GCSE IGCSE BTEC Science, GCE, AS, A2 Advanced subsidiary Chemistry A levels, IB Diploma and US K12 (K-12 grades) courses and examinations and revising for the various syllabuses and specifications. Exploring the site for lessons, plans, ideas for projects and coursework, professional development. Through hard work the site has been built up over the course of many years with no need of special pc software except FrontPage and Hot Potatoes (uvic) for quizzes and worksheets. It is used in the classroom, home learning-tutoring-schooling and guidance, private tuition, school retakes revision. Whether you are a teacher/tutor teaching, a student studying, using the pages as self-study guides for your science-chemistry studies etc. etc. I hope the site supports your endeavour. scientific investigations, educational development, scientific exhibitions, scientific adventures, science projects, fantasy science, science fiction, interesting science demonstrations, fascinating science experiments, science education conferences, scientific expeditions, scientific information and databases, revision tutoring resources for syllabuses specifications examinations, chemical physical biological forensic science, scientific applications, science-chemistry tuition courses