Question

By which method you can dilute a concentrated acid properly?
(A) Carefully replace unused or excess chemicals into their properly labelled containers from which they came.
(B) The rule is to add water to the concentrated acid slowly.
(C) Dispose of chemicals in the proper places following posted procedures. Do not return them to their original containers.
(D) Flush eyes with water at the eyewash fountain for at least 15 minutes, and then report the accident for further help.
(E) The rule is to add concentrated acid to water slowly.

Answer 1

Hint: When we work in a chemical laboratory, safety is of utmost importance. Whatever activities we perform in the laboratory, we should follow proper safety measures.

Complete answer:
A concentrated acid such as sulphuric acid has a strong affinity for water. The dissolution of concentrated acid in water is a highly exothermic reaction. An exothermic reaction is one in which heat is evolved (given out). An endothermic reaction is one in which heat energy is absorbed. Thus, during dissolution of concentrated acid in water, a large amount of heat is liberated. If we slowly add water to concentrated acid, then it may happen that concentrated acid may come out and spill on our skin and face. This is because concentrated acid has a large affinity for water and water will attract acid. In order to avoid the spillage of concentrated acid on our face and skin, we should change (reverse) the order of addition of concentrated acid and water. We should slowly add concentrated acid to water. This is purely out of safety considerations.

Hence, the correct option is the option (E).

Additional Information: Let us discuss other options as well.
We should not replace unused or excess chemicals into their properly labelled containers from which they came. This is to avoid contamination of the chemicals present in the original containers.
We should dispose of chemicals in the proper places following posted procedures. Do not return them to their original containers. This is to avoid contamination. This is not a part of the process of dilution of concentrated acid. This is just the disposal process for excess chemicals.
In case of spillage of chemicals on face, flush eyes with water at the eyewash fountain for at least 15 minutes, and then report the accident for further help. Again, this is not the process of dilution of concentrated acid. This is part of accidental measures.

Note: Concentric sulphuric acid will immediately burn the skin. It will remove water from the skin, a lot of heat will be liberated and a black, charred mass will be left out. So we should be extra careful while handling concentric sulphuric acid.