iodine is actually in the form of the triiodide ions in the presence of excess KI due to the I2 + I- I3-‚ equilibrium.) In the determination of ascorbic acid‚ both the KBrO3 and KIO3 methods employ a back titration with a standard thiosulfate solution of the excess Br2 or I2 generated by adding a precisely known amount of a primary standard KBrO3 or KIO3 solution to an ascorbic acid solution. In the case of the KBrO3 procedure‚ potassium iodide is added to react with Br2 to form I2. Br2 +
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Name: __________________________________ ( ) Class: 4Q HWA CHONG INSTITUTION PRELIMINARY EXAMINATION 2010 CHEMISTRY 5072 Paper 1 Time: 1 hour INSTRUCTIONS TO CANDIDATES Do not turn the pages over until you are told to do so. Write your name and index number on the answer sheet in the spaces provided. There are forty questions on this paper. Attempt all questions. For each question‚ there are four possible answers labelled A‚ B‚ C and D. Choose the one you consider correct and
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MECHANISM OF AQUEOUS HUMOR FORMATION There is a constant flow of aqueous humor through the anterior segment of the eye. The aqueous is formed by the ciliary process and flows from the posterior chamber to anterior chamber through the pupil and exits the eye at the angle. The secretion of aqueous humor generates the intraocular pressure required for an optically efficient globe. The flow of aqueous provides nutrition for the avascular ocular tissues that it bathes‚ the posterior surface of the
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2. Qualitative ORGANIC functional group tests in various homologous series | TEST FOR | TEST METHOD | OBSERVATIONS | TEST CHEMISTRY and comments | ALKENE or alkyne i.e. any non-aromatic unsaturated hydrocarbon with a double or triple carbon-carbon bond. | Bubble gas through‚ or add liquid to‚ a solution of bromine in hexane or water. | The orange/brown bromine rapidly decolourises‚ as a saturated colourless organic bromo-compound is formed. | R2C=CR2 + Br2 ==> BrR2C-CR2BrRCCR + 2Br2 ==> Br2RC-CRBr2R
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redox reaction is a combination of 2 parts‚ each called a half-reaction. * In Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g) * In the above reaction‚ the Zn(s) are converted to zinc ions in solution‚ Zn2+(aq). * Therefore: Zn(s) Zn2+(aq) + 2e- * Hydrogen ions in the solutions gain electrons and are converted to H2 gas. Thus becoming: 2H+(aq) + 2e- H2(g) * According to modern theory‚ the gain of electrons is called reduction. * According
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SERANGOON JUNIOR COLLEGE General Certificate of Education Advanced Level Higher 2 CHEMISTRY JC2 Preliminary Examination Paper 1 Multiple Choice Additional Materials: Data Booklet Optical Mark Sheet (OMS) 9647/01 23 August 2011 1 hour READ THESE INSTRUCTIONS FIRST On the separate multiple choice OMS given‚ write your name‚ FIN/NRIC and class in the spaces provided. Shade correctly your class and FIN/NRIC number. Eg. If your NRIC is S9306660Z‚ shade S9306660Z for the item “index number”. There
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Subject Content Most of the objectives specified in this section relate to Knowledge with Understanding‚ although some indication has been given as to where the skills of Handling Information and Solving Problems may be developed. Teachers are reminded that‚ in the written papers‚ 40% of the marks are allocated to these higher ’thinking’ skills. In almost every section‚ students should therefore be given practice at dealing with unfamiliar situations so that these higher thinking skills can be developed
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and it is a reaction between acidified hydrogen peroxide and potassium iodide: 2H+(aq) + 2I¯ (aq) + H[-1] 2O2 (l) ÕI2 (aq) + 2H2O2 (aq) Iodide ions are firstly oxidised by the hydrogen peroxide‚ as shown in the above equation. The iodine that is then produced reacts immediately reacts with thiosulphate ions as follows: I2 (aq) + 2Na2S2O3 (aq) Õ 2NaI (aq) + Na2S406 (aq) As soon as all of the thiosulphate ions have reacted with the iodine‚ the excess iodine molecules react with
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protons‚ 44 neutrons‚ 35 electrons (1) 81Br 35 protons‚ 46 neutrons‚ 35 electrons (1) 2 (iii) (1s2)2s22p63s23p63d104s24p5 (1) 1 [4] 2. (i) iodide has been converted to iodine (1) (with correct use and spelling of iodide and iodine) The 1st experiment shows that bromine is more reactive than iodine (1) The 2nd experiment shows that chlorine is more reactive than bromine (1) Accept 1 mark for 2nd and 3rd marking points if the
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beaker. Mix the contents well. Transfer the contents of the beaker to a 250 ml volumetric flask and make up the volume to the graduation mark‚ observing all of the usual procedures. The addition of sulphuric acid is vital as it prevents the Fe 2 ions from reacting with Prepare the potassium permanganate solution. Weigh out an approximate amount of KMnO 4 ‚ in a beaker‚ enough to make an approximately 0.02 M solution. Dissolve in dilute sulphuric acid‚ transfer and make up the solution in the
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