OCR A Jan 2011 Paper 1 Q2

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2 Sodium tartrate and copper(II) nitrate are both salts. (a) Sodium tartrate is a salt of tartaric acid. The formula of tartaric acid can be represented as HxA. In this formula, x is the number of H+ ions that can be replaced by metal ions to form salts. A student carries out a titration to find the value of x in the formula of tartaric acid, HxA. In the titration, 25.00 cm3 of 0.0500 mol dm3 tartaric acid, HxA, exactly reacts with 12.50 cm3 of 0.200 mol dm3 sodium hydroxide, NaOH. A solution of sodium tartrate is produced. (i) Calculate the amount, in mol, of HxA used. (ii) Calculate the amount, in mol, of NaOH used. amount =mol [1] (iii) Deduce the value for x in the formula of tartaric acid, HxA. amount =mol [1] x =[1]OCR 2011<br />
 (b) Copper(II) nitrate is a salt of nitric acid. (i) A student prepares a solution of copper(II) nitrate, Cu(NO3)2, by adding, with stirring, an excess of copper(II) oxide to some hot dilute nitric acid. Construct the equation for this reaction.[2] (ii) Copper(II) nitrate has ionic bonding. What is meant by the term ionic bonding?[1] (iii) Explain why a solution of copper(II) nitrate conducts electricity.[1] (iv) What is the oxidation number of nitrogen in Cu(NO3)2?[1] (c) Hydrated crystals of copper(II) nitrate can be prepared by allowing water to evaporate from a solution of copper(II) nitrate. Hydrated copper(II) nitrate has the empirical formula CuN2O12H12. Write the formula of hydrated copper(II) nitrate to show its water of crystallisation.[1] [Total: 9]OCR 2011 Turn over<br />

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