3 Disproportionation reaction

 

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3.1.3 halogens Page 2

Oxford Textbook Pages : 114 - 115

CGP Revision Guide Pages : 64 - 65

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Show Specification Ref : 3.1.3e, 3.1.3f

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Question 1 / 5

AQA Jan 2011 Paper 2 Q10 do not write outside the box a reactions that involve oxidation and reduction are used in a number of important industrial processes iodine can be extracted from seaweed by the oxidation of iodide ions in this extraction seaweed is heated with mno and concentrated sulfuric acid a i give the oxidation state of manganese in mno mark a ii write a half equation for the reaction of mno in acid to form mn ions and water as the only products mark a iii in terms of electrons state what happens to the iodide ions when they are oxidised mark b chlorine is used in water treatment when chlorine is added to cold water it reacts to form the acids hcl and hclo the following equilibrium is established cl aq h o i h aq cl aq hclo aq b i give the oxidation state of chlorine in cl and in hclo cl hclo marks wmp jan chem b ii deduce what happens to this equilibrium as the hclo reacts with bacteria in the water supply explain your answer do not write outside the box marks extra space c concentrated sulfuric acid is reduced when it reacts with solid potassium bromide concentrated sulfuric acid is not reduced when it reacts with solid potassium chloride c i write the two half equations for the following redox reaction h br h so br so h o half equation half equation marks c ii write an equation for the reaction of solid potassium chloride with concentrated sulfuric acid mark question continues on the next page turn over wmp jan chem c iii explain why chloride ions are weaker reducing agents than bromide ions do not write outside the box marks extra space end of questions copyright aqa and its licensors all rights reserved wmp jan chem
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Question 2 / 5

AQA Jan 2013 Paper 2 Q10 do not write outside the box chlorine is a powerful oxidising agent a write the simplest ionic equation for the reaction between chlorine and aqueous potassium bromide state what is observed when this reaction occurs marks extra space b write an equation for the reaction between chlorine and cold dilute aqueous sodium hydroxide give a major use for the solution that is formed by this reaction give the iupac name of the chlorine containing compound formed in this reaction in which chlorine has an oxidation state of marks extra space wmp jan chem c write an equation for the equilibrium reaction that occurs when chlorine gas reacts with cold water do not write outside the box give one reason why chlorine is used for the treatment of drinking water even though the gas is very toxic marks extra space d state how you could test a sample of water to show that it contains chloride ions in your answer give a reagent one observation and the simplest ionic equation for the reaction with the reagent marks extra space end of questions wmp jan chem
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Question 3 / 5

AQA Jun 2010 Paper 2 Q7 do not write outside the box chlorine is a useful industrial chemical a chlorine gas is used in the manufacture of chlorine containing organic compounds a i write equations for the following steps in the mechanism for the reaction of chlorine with ethane to form chloroethane ch ch cl initiation step first propagation step second propagation step a termination step producing butane marks a ii give one essential condition and name the type of mechanism in this reaction of chlorine with ethane essential condition type of mechanism marks wmp jun chem do not write outside the box b chlorine reacts with cold water b i write an equation for this reaction mark b ii give one large scale application of the use of chlorine in water explain why it is used in this application even though chlorine is very toxic do not include cost example of application explanation of use marks b iii two different chlorine containing compounds are formed when chlorine reacts with cold dilute sodium hydroxide solution one of these compounds is sodium chloride name the other chlorine containing compound formed mark c chlorine is used in the extraction of bromine from seawater c i write the simplest ionic equation for the reaction of chlorine with bromide ions mark c ii explain why bromine has a higher boiling point than chlorine marks turn over wmp jun chem
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Question 4 / 5

AQA Jun 2012 Paper 2 Q9 do not write outside the box a student investigated the chemistry of the halogens and the halide ions a in the first two tests the student made the following observations test observation add chlorine water to aqueous potassium iodide solution the colourless solution turned a brown colour add silver nitrate solution to aqueous potassium chloride solution the colourless solution produced a white precipitate a i identify the species responsible for the brown colour in test write the simplest ionic equation for the reaction that has taken place in test state the type of reaction that has taken place in test marks extra space a ii name the species responsible for the white precipitate in test write the simplest ionic equation for the reaction that has taken place in test state what would be observed when an excess of dilute ammonia solution is added to the white precipitate obtained in test marks extra space wmp jun chem b in two further tests the student made the following observations do not write outside the box test observation add concentrated sulfuric acid to solid potassium chloride the white solid produced misty white fumes which turned blue litmus paper to red add concentrated sulfuric acid to solid potassium iodide the white solid turned black a gas was released that smelled of rotten eggs a yellow solid was formed b i write the simplest ionic equation for the reaction that has taken place in test identify the species responsible for the misty white fumes produced in test marks extra space b ii the student had read in a textbook that the equation for one of the reactions in test is as follows h i h so i h s h o write the two half equations for this reaction state the role of the sulfuric acid and identify the yellow solid that is also observed in test marks extra space question continues on the next page turn over wmp jun chem do not write outside the box b iii the student knew that bromine can be used for killing microorganisms in swimming pool water the following equilibrium is established when bromine is added to cold water br i h o i hbro aq h aq br aq use le chatelier s principle to explain why this equilibrium moves to the right when sodium hydroxide solution is added to a solution containing dissolved bromine deduce why bromine can be used for killing microorganisms in swimming pool water even though bromine is toxic marks extra space end of questions wmp jun chem
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Question 5 / 5

AQA Jun 2014 Paper 2 Q6 do not write outside the box this question is about group chemistry a sea water is a major source of iodine the iodine extracted from sea water is impure it is purified in a two stage process stage stage l h o so hl h so hl cl l hcl a i state the initial oxidation state and the final oxidation state of sulfur in stage marks oxidation state of s in so oxidation state of s in h so a ii state in terms of electrons what has happened to chlorine in stage mark b when concentrated sulfuric acid is added to potassium iodide iodine is formed in the following redox equations ki h so khso l s h o ki h so khso l h s h o b i balance the equation for the reaction that forms sulfur b ii deduce the half equation for the formation of iodine from iodide ions mark mark b iii deduce the half equation for the formation of hydrogen sulfide from concentrated sulfuric acid mark question continues on the next page turn over wmp jun chem do not write outside the box c a yellow precipitate is formed when silver nitrate solution acidified with dilute nitric acid is added to an aqueous solution containing iodide ions c i write the simplest ionic equation for the formation of the yellow precipitate mark c ii state what is observed when concentrated ammonia solution is added to this yellow precipitate mark c iii state why the silver nitrate solution is acidified when testing for iodide ions mark c iv explain why dilute hydrochloric acid is not used to acidify the silver nitrate solution in this test for iodide ions mark wmp jun chem do not write outside the box d chlorine is toxic to humans this toxicity does not prevent the large scale use of chlorine in water treatment d i give one reason why water is treated with chlorine mark d ii explain why the toxicity of chlorine does not prevent this use mark d iii write an equation for the reaction of chlorine with cold water mark e give the formulas of the two different chlorine containing compounds that are formed when chlorine reacts with cold dilute aqueous sodium hydroxide mark formula formula turn over for the next question turn over wmp jun chem
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