Understanding Acid Dilution Safety

This question asks us to evaluate two statements about safely diluting acids.

Analyzing Assertion (A): Safe Dilution Practice

Assertion (A) states: "It is recommended that acid should be added to water for diluting the acid and not vice-versa."

• This is a fundamental safety rule taught in chemistry. When we dilute a concentrated acid, we are essentially reducing its concentration by adding more solvent, which is typically water.
• The correct procedure involves slowly adding the concentrated acid to a larger volume of water while stirring.
• Adding water to concentrated acid is extremely dangerous because it can cause the water to boil rapidly and splash the corrosive acid.

Therefore, Assertion (A) is a true statement representing a critical safety guideline.

Explaining the Reason (R): Exothermic Nature

Reason (R) states: "Dilution of acid is a highly exothermic reaction."

• An exothermic reaction is a chemical process that releases energy, usually in the form of heat.
• When concentrated acids like sulfuric acid (H₂SO₄) dissolve in water, the process releases a significant amount of heat. This is due to the strong interactions between the acid molecules and water molecules.
• The heat generated can be substantial, enough to boil the solution if not managed properly.

Therefore, Reason (R) is also a true statement.

Connecting Reason to Assertion: The 'Why' Behind the Rule

Now, let's see if the reason explains the assertion. The assertion recommends adding acid to water. The reason explains that this process is exothermic (releases heat). Why does this matter?

• When you add a small amount of acid to a large amount of water (as recommended), the large volume of water can absorb and dissipate the heat generated by the exothermic reaction effectively. This prevents the solution from reaching dangerously high temperatures.
• Conversely, if you add water to a concentrated acid (the opposite of the recommendation), the small initial amount of water added gets overwhelmed by the heat released. It can quickly boil away, causing the concentrated acid to splash out violently.

The fact that the dilution is a highly exothermic reaction (Reason R) directly explains *why* it is safer to add the acid slowly to water, rather than adding water to the acid (Assertion A). The heat management strategy is key.

Conclusion

Both Assertion (A) and Reason (R) are factually correct statements. Furthermore, Reason (R) provides the correct scientific explanation for why the safety procedure described in Assertion (A) is essential.