With a suitable activity show that sulphur burns in air to form a compound which is acidic in nature.

Explanation

1. Take a small amount of sulphur powder on a spatula.
2. Now burn this powder by placing a tube in a inverted position over the spatula as shown in the figure.
3. The fumes produced as a result of burning of sulphur, will get collected in the tube.
4. Place the tube in vertical position and immediately add some water to it.
5. Shake the tube so that the fumes may completely dissolve.
6. Add a few drops of blue litmus to a portion of the solution. It will acquire red colour which shows that it is of acidic nature.
7. To another portion, add a few drops of red litmus solution. No colour change will be noticed. This shows that the solution is not acidic.
Explanation : Sulphur burns in air to form sulphur dioxide which escapes from the tube as fumes with pungent and suffocating smell. The gas produced readily dissolves in water to form sulphurous acid `(H_(2)SO_(3))`. The solution is therefore, acidic. It will change the colour of blue litmus to red.
`S(g) + O_(2)(g) overset("heat")rarrSO_(2)(g) overset(H_(2)O)rarrunderset("Sulphurous acid")(H_(2)SO_(3)(aq))`