Edexcel Jun 2014 (IAL) Paper 6 Q1 (with explained solutions) |

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Edexcel Jun 2014 (IAL) Paper 6 Q1

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Answer ALL the questions. Write your answers in the spaces provided. 1 H is an aqueous solution of chromium(III) sulfate. (a) What is the colour of the solution? (1)(b) Describe what you would see when sodium hydroxide solution is added to H, drop by drop, until the sodium hydroxide is in excess. (2)(c) When hydrogen peroxide is added to the reaction mixture formed in (b), a yellow solution is formed. Give the formula of the ion responsible for the yellow colour and state the type of reaction which has produced this ion. (2) Ion formulaReaction type(Total for Question 1 = 5 marks) *P42981A0212*<br />

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Question Number 1(a) Mark Reject Blue Blue-green Grey-green Blue-violet Acceptable Answers Green OR Green (Cr3+) IGNORE additional information unless another wrong colour. ALLOW Shades of green like: pale green light green dark green ALLOW Violet / purple / red-violet / red-purple / mauve / ruby-violet / green-violet WCH0601 1406<br />
Question Number 1(b) Mark Acceptable Answers Reject Green / grey-green / grey-blue precipitate / ppt / ppte (of Cr(OH)3 / [Cr(H2O)3(OH)3]) ALLOW recognisable spelling of state eg percipitate (1) Second mark depends on first mark (or near miss such as incorrect formula of precipitate / incorrect colour of ppt) Dissolves (to give green solution) OR Green solution forms (of [Cr(OH)6]3-) (1) IGNORE shades of colour: Light / dark etc Other wrong descriptions like effervescence Incorrect formula for example Cr(H2O)2(OH)4]- Dissolves to give a yellow / blue solution Incorrect formula for example CrO4 2- WCH0601 1406<br />
Question Number 1(c) Mark Acceptable Answers Reject 2 2 (1) CrO4 OR CrO4 Check the charge is correct IGNORE brackets eg [CrO4]2- Oxidation / redox (reaction) Ignore references to Cr3+, Cr6+, loss/gain and loss of electrons, deprotonation (1) Mark each part independently. 2 CrO4 Cr2O7 Reduction Reduction / redox Redox / reduction References to Cr2+ Gain of electrons alone Total for Question 1 = 5 marks WCH0601 1406<br />

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