Edexcel Jun 2010 Paper 6 Q1 (with explained solutions) |

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Edexcel Jun 2010 Paper 6 Q1

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PMT (1) (1) (1) (2) Answer ALL the questions. Write your answers in the spaces provided. 1 Compound A is a salt containing one cation and one anion. Complete the following table by filling in the inferences column. Test (a) Observe the appearance of A. Observations A is a yellow crystalline solid. Inferences (b) Carry out a flame test on A. Persistent bright yellow flame colour. A dissolves to form an orange solution. Ions formed areOrange solution turns green. (c) Add 5cm3 of (d) dilute sulfuric acid to 0.5g of A. To the solution obtained in (c), add about 10 drops of ethanol and warm the mixture gently. (e) Divide the green solution from (d) into two equal portions. To one portion add sodium hydroxide solution a little at a time until in excess. Green precipitate forms which dissolves in excess sodium hydroxide to form a green solution. Green precipitate isGreen ions formed in solution are(2) *N36508A0216*<br />
PMT Observations The solution turns pale blue. Inferences Pale blue ions formed are Test To the second portion of the solution, add zinc powder. (f) (g) The pale blue solution turns green. Filter the mixture formed in (f) to remove the excess zinc and then shake the filtrate vigorously.Role of zincGreen ions formed are (2)Explanation(2) (Total for Question 1 = 11 marks) *N36508A0316* Turn over<br />

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Question Number 1 (a) Question Number 1 (b) Question Number 1 (c) Question Number 1 (d) Question Number 1 (e) Acceptable Answers Compound contains a transition metal (ion) / Compound contains chromate((VI)) / CrO4 Allow any yellow salt (name or correct formula) Allow transition element / metal (present) Ignore d block Ignore any cation included 2 Reject Dichromate oxides Cr6+ Mark Mark Mark Reject Na Anion Reject Cr(VI) Cr6+ Reject Cr6+ Mark Mark Reject Cr2O3 Cr3+ Cr3+(aq) Acceptable Answers Sodium (ions) present / Na+ 2 + 2H+ (cid:138) Cr2O7 Acceptable Answers dichromate(VI) / dichromate / Cr2O7 2CrO4 Ignore references to the other ions present (Na+, 2H+, SO4 No TE 2 + H2O 2 / 2) Acceptable Answers 2 / dichromate((VI))(allow Cr(VI)) is Cr2O7 reduced (by the ethanol) / the ethanol is 2 (allow Cr(VI))) / the oxidized (by Cr2O7 ethanol forms ethanal / ethanoic acid (1) Cr3+ / chromium(III) / Cr(III) formed (1) Allow fully balanced ionic half-equation (2) No TE Acceptable Answers Precipitate chromium(III) hydroxide / Cr(OH)3 / Cr(OH)3(H2O)3 (1) Solution chromate(III) / tetrahydroxochromate(III) / hexahydroxochromate(III) / Cr(OH)4 Cr(OH)6 Allow hydrated forms / CrO2 Allow chromium hydroxide if Cr3+ Allow Cr(OH)5 Ignore number of water ligands - / CrO3 3 (1)/ 3- 2- 6CH0801 1006 3/14<br />
Reject Cu2+ Mark Reject Mark Question Number 1 (f) Question Number 1 (g) 2+ chromium(II) / Cr(II) (1) Acceptable Answers Pale blue ions Cr2+ / Cr(H2O)n Role of zinc Reducing agent / Reduces / Reduction / providing electrons (1) Acceptable Answers Green ions Cr3+/ chromium(III) / Cr(III) (1) Explanation The Cr2+ / chromium(II) / Cr(II) (allow blue species) is oxidized by (oxygen in) the air (1) Ignore water ligands Allow oxidized by oxygen 6CH0801 1006 4/14<br />

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