17 (A410U10-1) Examiner only 12. Chlorine is one of the most widely used elements, and compounds containing chlorine atoms have a huge range of uses in the home and in industry. (a) Give one large scale use of the element chlorine. [1] (b) Chlorine reacts with hot concentrated sodium hydroxide solution to form two chlorine-containing products. Write the equation for this reaction. [1] (c) Chlorine can be used to produce bromine from the bromide ions present in seawater. An excess of chlorine is usually used in this process. In one experiment, a volume of 2.00 dm3 of chlorine gas was bubbled into seawater at 298 K under 1 atm pressure. A mass of 9.4 g of bromine was produced. Calculate the percentage of chlorine that remains unreacted at the end of the experiment, giving your answer to an appropriate number of significant figures. [3] Percentage of chlorine unreacted = ....................................................... % © WJEC CBAC Ltd. Turn over. (A410U10-1) (d) Chlorine-containing compounds can be studied using mass spectrometry. (i) Explain how ions are formed and separated in the mass spectrometer. [2] (ii) The diagram below shows part of the mass spectrum of a chlorine-containing compound. There are no other significant peaks near this group of peaks and adjacent peaks are two atomic mass units apart. © WJEC CBAC Ltd. m/z Abundance 18 Examiner only 19 (A410U10-1) Examiner only I. State how many chlorine atoms are present in these ions, giving a reason for your answer. [2] II. The height of the first peak is 54 and the height of the final peak is 2. Explain the ratio of these peak heights. [2] (e) Chlorine can form many compounds of general formula AB3, for example AlCl3 and ClF3. (i) Draw the shape of the AlCl3 molecule, giving its bond angle(s). [1] (ii) Explain why the molecule AlCl3 often forms dimers. [2] © WJEC CBAC Ltd. Turn over. (A410U10-1) 20 Examiner only (iii) Use the principles of valence shell electron pair repulsion theory to explain why the shape of ClF3 is not the same as that of BF3. You do not need to identify the shape of the ClF3 molecule. [2] © WJEC CBAC Ltd. 16