WJEC Chemistry for AS Level: Revision Workbook

Q1 (a) Precipitation reactions are often used for identification of unknown ions in solution. Write ionic equations for the reactions occurring in each of the following chemical tests. You should include state symbols. (i) Barium chloride is used to test for sulfate ions in solution. A white precipitate of barium sulfate is a positive result. [2] ......................................................................................................................................................................................................................................................................................................................................... (ii) Sodium hydroxide solution is used to test for Fe 2+ ions in solution. A dark green precipitate of iron(II) hydroxide is a positive result. [2] ......................................................................................................................................................................................................................................................................................................................................... (b) One method of testing for chlorine gas is to bubble the gas through a solution of sodium bromide. A positive result is an orange solution containing aqueous bromine. (i) Write an ionic equation for this reaction. [2] ......................................................................................................................................................................................................................................................................................................................................... (ii) Use oxidation states to show that this is a redox reaction. [2] ......................................................................................................................................................................................................................................................................................................................................... ......................................................................................................................................................................................................................................................................................................................................... ......................................................................................................................................................................................................................................................................................................................................... Q2 (a) When ethanoic acid is added to copper(II) carbonate, the salt produced is copper(II) ethanoate amongst other products. Write the equation for this reaction. [2] ......................................................................................................................................................................................................................................................................................................................................... (b) When any acid is added to a solution of sodium thiosulfate, Na 2 S 2 O 3 , the solution turns cloudy as sulfur forms and sulfur dioxide gas is released. 2H + + S 2 O 3 2− r S + SO 2 + H 2 O Find the oxidation states of sulfur in all the sulfur-containing species in the reaction. [2] S 2 O 3 2− .......................................................................................................................................................................................... S .......................................................................................................................................................................................................... SO 2 .................................................................................................................................................................................................. 12 | WJEC Chemistry for AS Level: Revision Workbook | Unit 1: The Language of Chemistry, Structure of Matter and Simple Reactions