OCR A Jan 2010 Paper 1 Q2

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2 A student carries out experiments using acids, bases and salts. (a) Calcium nitrate, Ca(NO3)2, is an example of a salt. The student prepares a solution of calcium nitrate by reacting dilute nitric acid, HNO3, with the base calcium hydroxide, Ca(OH)2. (i) Why is calcium nitrate an example of a salt?[1] (ii) Write the equation for the reaction between dilute nitric acid and calcium hydroxide. Include state symbols.[2] (iii) Explain how the hydroxide ion in aqueous calcium hydroxide acts as a base when it neutralises dilute nitric acid.[1]OCR 2010<br />
 (b) A student carries out a titration to find the concentration of some sulfuric acid. The student finds that 25.00 cm3 of 0.0880 mol dm3 aqueous sodium hydroxide, NaOH, is neutralised by 17.60 cm3 of dilute sulfuric acid, H2SO4. H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l) (i) Calculate the amount, in moles, of NaOH used. (ii) Determine the amount, in moles, of H2SO4 used. answer =mol [1] (iii) Calculate the concentration, in mol dm3, of the sulfuric acid. answer =mol [1] answer =mol dm3 [1] (c) After carrying out the titration in (b), the student left the resulting solution to crystallise. White crystals were formed, with a formula of Na2SO4x H2O and a molar mass of 322.1 g mol1. (i) What term is given to the x H2O part of the formula?[1] (ii) Using the molar mass of the crystals, calculate the value of x .OCR 2010 answer =[2] [Total: 10] Turn over<br />

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