Getting multicolored precipitations
name: Getting multicolored precipitations by ion exchange reactions
Be careful with the different chemical reagents. Use protective gloves and googles when you work with hydrochloric acid.
Always follow general safety
recommendations. Please note that conducting chemistry
experiments you must comply with the relevant legal procedures in
In this experiment the ability of substances to react with specific reagents is used for detection of inorganic ions in the solutions. These reactions are called qualitative reactions. A Qualitative reaction is a reaction that allows us to say whether there is a substance in the solution or not, but does not allow say how much of it there is.
For the detection of carbonate CO32- ions we should add a small amount of acid to the solution. An Ion exchange reaction occurs forming carbonic acid. But carbonic acid is unstable; it decomposes forming carbon dioxide and water:
Na2CO3 + 2HCl → CO2 + H2O + 2NaCl.
We can detect chloride Cl- ions in the solution by adding silver ions. A White precipitate forms as a result of this reaction:
NaCl + AgNO3 → AgCl + NaNO3. Also, the silver nitrate solution can be used to detect bromine Br- and iodine I- ions.
Adding barium chloride to the solution with sulphate SO42-ions can show presence of these ions in the solution:
Na2SO4 + BaNO3 → BaSO4 + 2NaNO3.
This is a qualitative reaction for detection of barium Ba2+ and sulphate SO42- ions.