What is the proper procedure for adding water and acid together?

Question

why is it important to follow this procedure?

Answer 1

There's a poorly rhyming saying most chemists should know:

"Do as you ought' to, add acid to water"

Answer 2

The proper procedure is to add the acid slowly to the water. The reason for this is that a large amount of energy is released as acid and water mix (the enthalpy of solvation). Mixing the acid and water quickly releases this energy all at once, and the solution could boil and spatter. Furthermore, adding the acid to the water rather than vice versa ensures that any accidental spattering involves dilute, rather than concentrated, solution, at least near the beginning. In the case of H2SO4 (sulfuric acid), the acid is denser than the water, so adding the acid to the water allows the acid to sink to the bottom.

Answer 3

Make sure you add a very small amount of the acid to the water. Never add the water to a concentrated acid solution. Concentrated acids such as Sulphuric acid are powerful oxidising agents. If you added a large amount of water to conc acid it would explode. The reaction is exothermic and gives off loads of heat.

Always best to titrate a small amount of acid to a larger solution of water.