Question

Take 5 mL water in a test tube and slowly and concentrated sulphuric acid. Touch the bottom of the test tube. What do you observe?

Answer 1

If water is added to the concentrated sulphuric acid, it can boil and spit dangerously. One should always add the acid to the water rather than the water to the acid. The necessity for this safety precaution is due to the relative densities of these two liquids. Water is less dense than sulphuric acid, meaning water will tend to float on top of this acid. When H2SO4 is dissolved in water it dissociates to produce ions. The H+ ions react with the water molecules to form the hydrogen ions. The dissociation takes place in two steps, as in:
H2SO4 + H2O ↔ H3O+ HSO4-
The HSO4- ion also dissociates to a small degree:
HSO4- + H2O → H3O+ + (SO4)2-
The reaction of water (H2O) and sulphuric acid (H2SO4) is very exothermic and gives out heat