Bromine extraction GCSE, Schemes and Mind Maps of Chemistry

Download Bromine extraction GCSE and more Schemes and Mind Maps Chemistry in PDF only on Docsity! 8.2 The halogens Stretch and challenge OCR Chemistry A Bromine from seawater Specification reference • 3.1.3 Introduction The aim of this activity is to extend your knowledge of the production of one of the halogens, bromine. In the course of studying bromine production, you will also be practicing mass calculations and writing equations, and showing that you understand the trend in oxidising ability of the halogens. Learning outcomes After completing the worksheet you should be able to: • understand how bromine is produced • construct balanced chemical equations and redox equations • understand the trend in oxidising ability of the halogens. Background The majority of the ‘salt’ in seawater is sodium chloride. However, there are other salts present, including some bromides. The mass of bromide ions in seawater may be low at 0.07 g dm−3 of water, but this is a high enough concentration to make extracting bromine from seawater economically viable. Bromine is produced in the UK at Amlwch in Anglesey, Wales. Questions 1 Calculate the mass in tonnes of ocean water that contains 1 tonne of bromide ions. (Assume that 1 dm3 of ocean water has a mass of 1 kg.) (1 mark) 2 At Amlwch approximately 22 000 tonnes of ocean water are used to produce 1 tonne of bromine. Using your answer from question 1, calculate the percentage yield of this process. (2 marks) At the production plant in Amlwch, seawater is first pumped from the Irish Sea through a large pipeline. It is acidified with sulfuric acid at this stage to prevent the bromine that is going to be produced from it, and chlorine used in its production, from reacting with water. (This reaction only occurs at higher pH, hence adding sulfuric acid prevents it.) 3 Write a balanced equation to show the reaction of bromine with water. (2 marks) 4 Write a balanced equation to show the reaction of chlorine with water. (2 marks) Chlorine is then injected into the acidified seawater. It displaces the bromide ions by a redox reaction. © Oxford University Press 2015 www.oxfordsecondary.co.uk/acknowledgements This resource sheet may have been changed from the original 1