hi guys this video is about the test for sulphate ions so let's have a look at the experiment first and then crack on with the equations so here is my sample which contains some sulfate ions the first thing I'm going to do when I'm testing is I'm gonna add some dilute hydrochloric acid now the reason that we do this is to remove impurities this means that if there's any carbonate or anything else in there that I don't want to be then it will react with the acid and won't react with the reagent that tests for the sulfate ions so the actual test itself involves testing sulphate ions using barium ions and normally we use barium chloride as our reagent so let's watch what happens when I add the barium chloride to myself 8 ions so hopefully what you can see is this is giving me a nice bright white precipitate and that indicates the presence of sulphate ions let's have a look at the equations to really show what's happening when I test for those sulfate ions remember a sulfate is so4 2 - and for the sake of it today I'm going to pretend that the sample I was using was magnesium sulfate in reality it could be any sulfate it doesn't really matter when it reacts with the barium chloride what you get is you get a double substitution happening and this results in you're making magnesium chloride and barium sulfate now remember if you're trying to work out which of the products is the one that's the precipitate it's always the one that contains the ions that you're actually testing for so in this case I'm testing for a sulfate so therefore the white precipitate the solid product has to be the barium sulfate if I was to just write this out as an ionic equation the ions that are really reacting are just the sulfate ion with the barium two plus iron to give that bare sulphate solid and that is all for the test for the sulphate ion using barium chloride