Question

whie diluting an acid ,why it is recommended that the acid should be added to water not

Answer 1

beacuse while adding water to acid it forms a highly exothermic reaction which can make the water steam and the steam can cause harmful damage and even the boiling water can be very dangerous 
So it is recommende that acid to water and not water to acid

Answer 2

water is not suggested to add to acid as it results in liberation of large amount of heat and this type of reactions are exothermic reactions.so adding water to acid may spoil the reaction..