5 Titration curves and Indicators

 

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Oxford Textbook Pages : 326 - 330

CGP Revision Guide Pages : 88 - 89

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Show Specification Ref : 3.1.12.5

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Question 1 / 5

AQA Jan 2010 Paper 4 Q2 areas outside the box will not be scanned for marking in this question give all values of ph to decimal places a i write an expression for the term ph mark a ii calculate the concentration in mol dm of an aqueous solution of sulfuric acid that has a ph of marks b a student carried out a titration by adding an aqueous solution of sodium hydroxide from a burette to an aqueous solution of ethanoic acid the end point was reached when cm of the sodium hydroxide solution had been added to cm of mol dm ethanoic acid b i write an equation for the reaction between sodium hydroxide and ethanoic acid mark b ii calculate the concentration in mol dm of the sodium hydroxide solution used marks wmp jan chem b iii a list of indicators is shown below areas outside the box will not be scanned for marking indicator thymol blue bromophenol blue litmus cresol purple ph range select from the list the most suitable indicator for the end point of this titration mark b iv suggest why the concentration of sodium hydroxide in a solution slowly decreases when left open to air mark c at k the value of the acid dissociation constant ka for ethanoic acid in aqueous solution is mol dm c i write an expression for the acid dissociation constant ka for ethanoic acid mark c ii calculate the ph of mol dm ethanoic acid at this temperature marks extra space question continues on the next page turn over wmp jan chem areas outside the box will not be scanned for marking c iii calculate the ph of the buffer solution formed when cm of mol dm potassium hydroxide are added to cm of mol dm ethanoic acid marks extra space wmp jan chem there are no questions printed on this page do not write on this page answer in the spaces provided turn over wmp jan chem
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Question 2 / 5

AQA Jun 2011 Paper 4 Q1 section a answer all questions in the spaces provided do not write outside the box titration curves labelled a b c and d for combinations of different aqueous solutions of acids and bases are shown below all solutions have a concentration of mol dm ph ph volume cm volume cm ph ph volume cm volume cm a in this part of the question write the appropriate letter in each box from the curves a b c and d choose the curve produced by the addition of ammonia to cm of hydrochloric acid sodium hydroxide to cm of ethanoic acid nitric acid to cm of potassium hydroxide marks wmp jun chem do not write outside the box b a table of acid base indicators is shown below the ph ranges over which the indicators change colour and their colours in acid and alkali are also shown indicator trapaeolin bromocresol green cresol purple alizarin yellow ph range colour in acid colour in alkali red yellow yellow yellow yellow blue purple orange b i select from the table an indicator that could be used in the titration that produces curve b but not in the titration that produces curve a mark b ii give the colour change at the end point of the titration that produces curve d when cresol purple is used as the indicator mark turn over for the next question turn over wmp jun chem
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Question 3 / 5

AQA Jun 2013 Paper 4 Q3 do not write outside the box a this question is about br nsted lowry acids of different strengths state the meaning of the term br nsted lowry acid mark b i write an expression for the acid dissociation constant ka for ethanoic acid mark b ii the value of ka for ethanoic acid is mol dm at c calculate the concentration of ethanoic acid in a solution of the acid that has a ph of marks c the value of ka for chloroethanoic acid clch cooh is mol dm at c c i write an equation for the dissociation of chloroethanoic acid in aqueous solution mark c ii suggest why chloroethanoic acid is a stronger acid than ethanoic acid marks wmp jun chem d p and q are acids x and y are bases the table shows the strength of each acid and base do not write outside the box acids bases strong weak strong weak the two acids were titrated separately with the two bases using methyl orange as indicator the titrations were then repeated using phenolphthalein as indicator the ph range for methyl orange is the ph range for phenolphthalein is for each of the following titrations select the letter a b c or d for the correct statement about the indicator s that would give a precise end point write your answer in the box provided both indicators give a precise end point only methyl orange gives a precise end point only phenolphthalein gives a precise end point neither indicator gives a precise end point d i acid p with base x d ii acid q with base x d iii acid q with base y question continues on the next page mark mark mark turn over wmp jun chem do not write outside the box using a burette cm of mol dm sulfuric acid were added to a conical flask containing cm of mol dm aqueous sodium hydroxide assume that the sulfuric acid is fully dissociated calculate the ph of the solution formed give your answer to decimal places e marks extra space wmp jun chem
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Question 4 / 5

AQA Jan 2012 Paper 5 Q7 section b answer all questions in the spaces provided do not write outside the box a due to their electron arrangements transition metals have characteristic properties including catalytic action and the formation of complexes with different shapes give two other characteristic properties of transition metals for each property illustrate your answer with a transition metal of your choice marks b other than octahedral there are several different shapes shown by transition metal complexes name three of these shapes and for each one give the formula of a complex with that shape marks wmp jan chem do not write outside the box c it is possible for group metal ions to form complexes for example the ca h o ion in hard water reacts with edta ions to form a complex ion in a similar manner to hydrated transition metal ions this reaction can be used in a titration to measure the concentration of calcium ions in hard water c i write an equation for the equilibrium that is established when hydrated calcium ions react with edta ions mark c ii explain why the equilibrium in part c i is displaced almost completely to the right to form the edta complex marks c iii in a titration cm of a mol dm solution of edta reacted completely with the calcium ions in a cm sample of a saturated solution of calcium hydroxide calculate the mass of calcium hydroxide that was dissolved in dm of the calcium hydroxide solution marks extra space turn over wmp jan chem
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Question 5 / 5

AQA Jun 2016 Paper 5 Q9 a do not write outside the box a student weighed out a g sample of impure k fe c o h o and dissolved it in water this solution was added to a cm volumetric flask and made up to cm with distilled water a cm portion was pipetted into a conical flask and an excess of acid was added the mixture was heated to c and titrated with mol dm kmno solution cm of kmno solution were needed for a complete reaction in this titration only the c o ions react with the kmno solution the reaction between c o explain what is meant by the term autocatalysed and identify the catalyst in the reaction marks ions is autocatalysed ions and mno b select from the list the most suitable substance used to acidify the solution in the conical flask put a tick in the correct box mark h c o h so hcl hno wmp jun chem c d the reaction between c o explain why the reaction is initially slow ions and mno ions is very slow at first do not write outside the box marks write an equation for the reaction between c o solution calculate the percentage purity of the original sample of k fe c o h o give your answer to significant figures ions and mno ions in acidic marks turn over wmp jun chem do not write outside the box e a solution of kmno has an unknown concentration describe briefly how colorimetry can be used to determine the concentration of this solution marks end of questions wmp jun chem
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