Assertion (A) : To dilute sulphuric acid, acid is added to water and not water to acid. Reason (R) : Specific heat of water is quite large.

Assertion (A) is true: concentrated sulphuric acid must be added to water because mixing with water is highly exothermic and could cause the mixture to splash or the container to break if done improperly [1]. Multiple safety sources explicitly state the correct procedure is to add acid to water to avoid boiling and splattering caused by the large heat release on dilution. Reason (R) — that the specific heat of water is quite large — is also true and provides the physical basis: water’s high heat capacity allows it to absorb much of the heat released on addition of acid, limiting temperature rise and reducing the likelihood of violent boiling and splashing. Thus R correctly explains A.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Activity 2.10 > p. 24