Why should acid always be added to water and not water to acid while preparing a dilute solution? What is the process of adding an acid or base to water called, and what type of process (exothermic/endothermic) is it?
Generated by claude-sonnet-4-6 · 2026-06-15 06:41 · grounding rag
Model Answer
Acid must always be added to water because mixing is highly exothermic. If water is added to acid, the heat generated can cause the mixture to splash out, causing burns, and may even crack the glass container due to excessive local heating. Adding acid slowly to water with stirring ensures safe dissipation of heat.
This process is called dilution. It is an exothermic process.
Source: Chapter 2, Section 2.2.1
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Explanation
- Examiners expect two points: (1) the safety reason — splashing/burns/breakage if water is added to acid, and (2) naming the process as dilution and identifying it as exothermic.
- The key phrase from the textbook is: "The acid must always be added slowly to water with constant stirring."
- Do not confuse dilution (exothermic) with endothermic reactions — this is a common mistake.