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Chemistry · L4 · Anion tests: sulfate, carbonate, nitrate

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Decision scheme for confirming sulfate, carbonate, or nitrate ions in an unknown, from choosing a reagent to reading the positive result.

by @openstemUpdated Chemistry
Unknown solution or solidWhich anion do you suspect?Acidify with dilute HCl, then add barium chloride solutionAdd dilute acid, e.g. dilute HClAdd freshly prepared iron(II) sulfate, then pour concentrated H2SO4 down the side of the tubeWhite precipitate that stays insoluble in the acid?Sulfate ion confirmed - barium sulfate precipitateSulfate absent - try another anionEffervescence, a gas is released?Bubble the gas through limewaterLimewater turns cloudy?Carbonate ion confirmed - carbon dioxide releasedGas is not carbon dioxide - try another anionCarbonate absentBrown ring forms at the junction of the two layers?Nitrate ion confirmed - brown ring complexNitrate absentSulfateCarbonateNitrateYesNo precipitate, or it dissolvesYesYesNoNo gasYesNo brown ring

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