Question

For diluting an acid, the acid should be poured carefully in water and not the reverse. Why?

Answer 1

because if you pour water in acid then the reaction become vigorous and the water splashes out causing damage.

Answer 2

because acid reacts with water liberates heat
when water is added to water it liberates heat but less amount
in reverse it liberates more heat and solution will vome out and causes burns to hand,sometimes there is a chance of breaking testtube