Testing for anions (group 7 halides, OH-, CO32- and SO42-) 0.0 / 5 ? ChemistryReactionsRedoxThe Periodic TableA2/A-levelAQA Created by: jamey_brewsterCreated on: 15-04-19 19:18 How are sulfate ions tested for? Add barium chloride solution acidified with HCL. 1 of 17 What is the positive result for sulfate ions? White precipitate of insoluble barium sulfate forms. 2 of 17 Why is the barium sulfate acidified with HCL? The HCL reacts with carbonate impurities often found in salts. These would give a false +ve result of a white barium carbonate precipitate. 3 of 17 Why can't sulfuric acid be used to acidify the barium sulfate? Contains sulfate ions so would give a false positive result. 4 of 17 What would be observed upon acidification of the barium sulfate if carbonate ions were present? Fizzing due to carbon dioxide. 5 of 17 What is used to test for halide ions? Silver nitrate solution, added dropwise. 6 of 17 Why is silver nitrate used instead of silver? Nitric acid reacts with any carbonates present to prevent formation of insoluble silver carbonate. 7 of 17 What is the result for fluorides? No precipitate 8 of 17 What is the result for chlorides? White AgCl precipitate 9 of 17 What is the result for bromides? Cream AgBr precipitate 10 of 17 What is the result for iodides? Pale yellow AgI precipitate 11 of 17 What can be used to differentiate between the silver halide precipitates? Ammonia solution 12 of 17 What is the result for AgCl? Dissolves in dilute ammonia to form [Ag(NH3)2]+ 13 of 17 What is the result for AgBr? Dissolves in concentrated ammonia to form [Ag(NH3)2]+ 14 of 17 What is the result for AgI? No visible change, as it is too insoluble to react with ammonia. 15 of 17 How are carbonate ions tested for? Add dilute acid - fizzing due to CO2 if carbonate present. Bubble gas through limewater - CO2 will turn it cloudy. 16 of 17 How are hydroxide ions tested for? Use litmus paper. OH- are alkaline so will turn red litmus paper blue. 17 of 17
Comments
No comments have yet been made