OCR A Jan 2012 Paper 1 Q2

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2 Calcium chloride, CaCl 2, can be made by different reactions. A student prepared hydrated calcium chloride by carrying out the following experiment. Step 1 The student added an excess of a solid calcium compound, X, to dilute hydrochloric acid. The mixture fizzed as the solid reacted. Step 2 The student filtered the mixture to give an aqueous solution of CaCl 2. Step 3 On evaporation, colourless crystals of hydrated calcium chloride were formed. (a) Describe a chemical test which the student could have carried out to prove that the filtrate contains aqueous chloride ions.[2] (b) A friend of the student suggested that solid X was calcium oxide. State one reason why the students friend was incorrect and suggest a possible identity of solid X. reason:solid X:[2] (c) Hydrated calcium chloride has a molar mass of 219.1 g mol1. (i) What is meant by the term hydrated calcium chloride?[1] (ii) Determine the formula of the hydrated calcium chloride. You must show your working.OCR 2012 formula =[2]<br />
 (d) Calcium chloride can also be formed by directly reacting calcium with chlorine gas. Draw a dot-and-crossdiagram to show the bonding in calcium chloride. Show outer electrons only. [2] (e) The student decided to prepare barium bromide, BaBr2, by directly reacting barium with bromine gas. The student was unsure whether this preparation would be more reactive or less reactive than the preparation of CaCl 2 in (d). Explain why the student was unsure of the relative reactivity of the two preparations.[2] [Total: 11]OCR 2012 Turn over<br />

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