Be careful with the different chemical reagents. Perform experiments in fume hood. Use protective gloves and googles when you work with sulphuric 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 ammonium nitrate NH4NO3 we used universal indicator paper. When we dissolved solid ammonium nitrate in the water, hydrolysis process occurred. Hydrolysis process is the exchange reaction between salt and water. A salt can be formed by a strong or weak base and a strong or weak acid. Different combinations of acids and bases define how the hydrolysis takes place. Ammonium nitrate is formed by a weak base and a strong acid. So when it reacts with water, a strong acid is formed:
NH4NO3 + H2O → NH4OH + HNO3.
And when we lower the strip of universal indicator paper into this solution, the indicator paper becomes red.
We can detect phosphate PO43- ions in the solution by adding silver ions. Yellow precipitate forms as a result of this reaction:
Na3PO4 + 3AgNO3 → Ag3PO4 + 3NaNO3.
We can detect nitrate NO3- ions in the solution using copper and concentrated sulphuric acid. Adding sulphuric acid to the sodium nitrate solution causes nitric acid formation:
2NaNO3 + H2SO4 → 2HNO3 + Na2SO4.
And now we have nitric acid in the solution. So when we add copper wire and heat the mixture, the RedOx reaction starts:
Cu + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O.
Copper nitrate Cu(NO3)2 makes the solution green. Nitrogen dioxide NO2 is a dark-red gas.