Edexcel Jun 2015 (IAL) Paper 3 Q2 (with explained solutions) |

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Edexcel Jun 2015 (IAL) Paper 3 Q2

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2 An organic compound, Z, has only one OH group. (a) State the test which confirms the presence of an OH group and give the result of a positive test. (2) TestResult(b) Name two series of organic compounds, with different general formulae, each of which has one OH group. (1)and(c) Neither red nor blue litmus paper changed colour when used to test an aqueous solution of Z. A different sample of Z was warmed with a mixture of aqueous potassium dichromate(VI) and sulfuric acid. No change was observed. What can be deduced about the identity of the functional group in Z from each of these observations? Justify your answer. (2) Test with litmus paperWarming with aqueous potassium dichromate(VI) and sulfuric acid*P44883A0416*<br />
(d) Z was investigated by measuring the volume of carbon dioxide formed on complete combustion. A sample of 0.10 mol of Z produced 9.6 dm3 of carbon dioxide. Under the conditions of the experiment, the molar volume of a gas is 24 dm3 mol1. Use this information to calculate the number of carbon atoms in one molecule of Z. Use the result of your calculation and your deduction in (c) to draw the displayed formula of Z. Show your working. (3) (e) Z has several isomers, only some of which contain an OH group. (i) Give one piece of evidence from their mass spectra which would show that two compounds could be isomers. (1)(ii) How could infrared spectroscopy be used to show that two isomers of Z both have an OH group? You are not required to give wavenumber values. (1)(Total for Question 2 = 10 marks) *P44883A0516* Turn over<br />

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Mark Acceptable Answers Reject TEST Add PCl5 / phosphorus(V) chloride / phosphorus pentachloride /SOCl2 / thionyl chloride / sulphur dichloride oxide (1) RESULT Mark depends on correct reagent, but allow PCl5 (aq) Steamy / misty / white fumes ALLOW Gas for fumes (1) Ignore incorrect identification of fumes OR TEST Add sodium / Na (1) RESULT Mark depends on correct reagent Effervescence / bubbling / fizzing Ignore incorrect identification of fumes and tests for products white solid (forms) / sodium dissolves mixture gets hot (1) Acidified PCl5 / PCl5 (aq) Acidified dichromate(VI) PCl3 Test to form an ester Any smoke Just HCl fumes Just gas turns litmus red Just hydrogen Question Number 2(a)<br />
Mark diol carboxyl cyclic alcohol specific alcohol eg ethanol Reject Mark Acceptable Answers Reject (primary / secondary / tertiary) Alcohol and carboxylic acid ALLOW ROH and RCOOH R2CHOH/ R3COH for ROH CnH2n+1OH for ROH RCO2H for RCOOH Phenol(s) (as one alternative) Fatty acid / alkanoic acid for carboxylic acid Acceptable Answers Z identified as tertiary alcohol (1) Justification: Any one from Test with litmus Not (carboxylic) acid because there is no change (in (blue) litmus paper) Its an alcohol because there is no change (in (red / blue) litmus paper) It is neutral /not an acid or an alkali because there is no change (in (red / blue) litmus paper) Test with dichromate It is a tertiary alcohol because it cant be oxidized (by acidified dichromate(VI))/ doesnt react with acidified dichromate(VI) It is not a primary or secondary alcohol because it cant be oxidized (by acidified dichromate(VI))/ doesnt react with acidified dichromate(VI) IGNORE Not an amine (1) If more than one justification is given, both must be correct Question Number 2(b) Question Number 2(c)<br />
Mark Acceptable Answers Reject Just 9.6/24 = 0.4 with no reference to what numbers refer to or if not applied CH3 CH3 C HO CH3 Only if bond clearly shown to the H of OH MP1 (0.1 mol Z produces) 0.4 mol CO2 OR 1 mol Z produces 4 mol CO2 (1) MP2 (dependent on MP1 awarded) So Z has 4C atoms ALLOW Formula shown with 4C (1) MP3 (stand alone) OR CH3 CH3 C OH CH3 ALLOW undisplayed CH3 and OH as above Skeletal formula OH (1) Question Number 2(d)<br />
Acceptable Answers Reject Same fragments Same m/e value for highest peak Similar for same Molecular ions have same m/e ALLOW same molecular ion isomers have same molar mass / molecular mass molecular ion with same mass same maximum m/e value same peak furthest to right same last peak Parent ion / M+ for molecular ion IGNORE Reference to peak heights Acceptable Answers Reject Mark Mark Absorption for C-OH They both have an (absorption) peak for (wavenumber of) alcohol / hydroxyl group / O-H ALLOW both have peak for OH / OH frequency / wavelength for wavenumber IGNORE wavenumber values have peak with specific shape for OH Total for Question 2 = 10 marks Question Number 2(e)(i) Question Number 2(e)(ii)<br />

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