Correct Option
The Assertion (A) states that for diluting sulphuric acid, acid should be added to water and not water to acid. This is a critical safety procedure in chemistry. The dilution of concentrated sulphuric acid is a highly exothermic process, releasing a significant amount of heat. If water is added directly to concentrated acid, the less dense water would initially float on the acid. The intense localized heat generated at the interface could cause the water to boil violently and explosively, leading to dangerous splashing of hot acid. Conversely, adding acid slowly to a larger volume of water allows the denser acid to sink and the heat to be dissipated over a greater volume, thereby reducing the risk of a sudden and violent reaction. Therefore, Assertion (A) is true.
The Reason (R) states that the specific heat of water is quite large. Water indeed possesses a high specific heat capacity (approximately 4.18 J/g°C or 1 cal/g°C). This property means that water can absorb a considerable amount of heat energy with only a relatively small increase in its own temperature. This characteristic is fundamental to many natural processes and chemical applications. Therefore, Reason (R) is true.
Furthermore, Reason (R) is the correct explanation for Assertion (A). The large specific heat capacity of water is crucial during the dilution process. When acid is added slowly to water, the water effectively absorbs the substantial heat released from the exothermic reaction. This prevents a rapid and dangerous temperature increase in the solution and mitigates the risk of explosive boiling or splashing, making the dilution process safer and more controllable. Thus, both Assertion (A) and Reason (R) are true, and Reason (R) correctly explains Assertion (A).
Incorrect Options
Option 2 is incorrect because Reason (R) does provide a correct and direct explanation for Assertion (A), as the high specific heat capacity of water is the primary reason for the safe dilution procedure. Options 3 and 4 are incorrect because both Assertion (A) and Reason (R) are factually accurate statements concerning chemical safety protocols and the physical properties of water, respectively.