OCR A Jun 2010 Paper 1 Q2

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2 Chemicals called acids have been known throughout history. The word acid comes from the Latin acidus meaning sour. Dilute sulfuric acid, H2SO4, is a common laboratory acid. (a) (i) State the formulae of two ions released when sulfuric acid is in aqueous solution.[2] (ii) A student adds a sample of solid potassium carbonate, K2CO3, to an excess of dilute sulfuric acid. Describe what the student would see and write the equation for the reaction which takes place.[3]OCR 2010<br />
 (b) Dilute sulfuric acid reacts with alkalis such as sodium hydroxide. Solid sodium hydroxide is known as caustic soda. It has a household use as a drain cleaner. A student believes a box of caustic soda has been accidentally contaminated. To prove this, the student dissolves 2.00 g of the impure caustic soda in water and the solution is made up to 250 cm3. 25.0 cm3 of this solution of caustic soda is neutralised by 24.60 cm3 of 0.100 mol dm3 dilute sulfuric acid. H2SO4(aq) + 2NaOH(aq) Na2SO4(aq) + 2H2O(l) (i) Calculate the amount, in moles, of H2SO4 used. (ii) Determine the amount, in moles, of NaOH in the 25.0 cm3 used. answer =mol [1] (iii) Calculate the percentage, by mass, of NaOH in the impure caustic soda. answer =mol [1]OCR 2010 answer =[3] [Total: 10] Turn over<br />

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