(A410U10-1) 18 Examiner only 10. Copper and cobalt are both considered to be transition elements whilst zinc is not. (a) Give a reason why zinc is not considered to be a transition element. [1] (b) Transition elements are able to form complex ions and these ions are usually coloured. Give the colour of the [Co(H2O)6]2+ ion. [1] ……………...................................................................................…………….. © WJEC CBAC Ltd. 19 (A410U10-1) Examiner only (c) When an aqueous solution containing Cu2+ ions is treated with a concentrated aqueous solution of ammonia a pale blue precipitate forms. This dissolves when more ammonia is added to form a royal blue solution, labelled A in the scheme below. (i) Identify the pale blue precipitate. [1] ........................................................................................................................ (ii) Some of the colour changes observed when other solutions are added to solution A are given in the following scheme. © WJEC CBAC Ltd. Turn over. royal blue solution, A pale blue solution, B green solution, C add dilute hydrochloric acid add concentrated ammonia solution add water add concentrated hydrochloric acid Identify the species causing these colours and use Le Chatelier’s principle to explain the changes that occur. Your answer should include appropriate equations. [6 QER] (A410U10-1) (d) Give another typical property of transition elements and use it to show that copper is a typical transition element but zinc is not. [2] © WJEC CBAC Ltd. 20 Examiner only 11 BLANK PAGE (A410U10-1) Turn over. 21 © WJEC CBAC Ltd.