Edexcel Jun 2015 (IAL) Paper 5 Q22

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22 Crystals of copper(II) sulfate dissolve in water to form a blue solution, A. When dilute aqueous ammonia is added to this solution, a pale blue precipitate, B, forms which dissolves in excess aqueous ammonia to form a dark blue solution, C. (a) (i) Give the formula of the copper species in A, B and C. You should include all of the ligands present in each species. (3) ABC(ii) Explain why solution A is coloured. (4)(iii) Explain why solution A is a different colour to solution C. (2)16 *P45074A01628*<br /> (b) A more concentrated solution of C may be prepared by using concentrated aqueous ammonia in place of dilute aqueous ammonia. The crystalline sulfate of C may be obtained by cooling the mixture in an ice bath and adding ethanol. The filtered crystals may be recrystallized using ethanol as the solvent. The steps of the recrystallization are summarised below. In the spaces provided, explain the purpose of each step, referring particularly to any words in bold type. (5) Step 1 The solid was dissolved in the minimum amount of hot ethanol.Step 2 The hot solution was filtered.Step 3 The filtrate was cooled in an ice bath.Step 4 The mixture was filtered using suction filtration.(Total for Question 22 = 14 marks) *P45074A01728* 17 Turn over<br />

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