Question

Why would you be advised to add hydrochloric acid dropwise, rather than in one go?

Answer 1

Do you ask in the context of a titration......?

Explanation:

Now you do have the order of addition right; you always add acid to water, and never the reverse. If you ask why we perform a titration dropwise, then clearly it is because we wish to determine the stoichiometric end point precisely. Moreover, when we do a titration, we typically deal with concentrations that are `0.1-0.5*mol*L^-1` in strength; these are fairly dilute solutions.

When a concentrated acid is added to water, say `HCl` or `H_2SO_4`, the solution will heat up as the hydronium ions are solvated....i.e.

`HX(aq) + H_2O(l) rarr H_3O^+ + X^(-) + Delta`

Dropwise addition can thus moderate the evolution of heat.