Difficulty: Easy

Average Score: 100%

When an acid is added to a base in water, which of the following happens?

Rationale

The pH of the solution changes.

When an acid is added to a base in water, a neutralization reaction occurs that typically results in the formation of water and a salt, leading to a change in pH. The extent of this change depends on the strength and concentrations of the acid and base involved.

A (The pH of the solution changes.) CORRECT

This statement accurately reflects the fundamental outcome of an acid-base reaction. The addition of an acid to a base alters the concentration of hydrogen ions (H⁺) and hydroxide ions (OH⁻) in the solution, resulting in a shift in pH. This change is a key characteristic of neutralization reactions.

B (The solution becomes much cooler.) YOUR ANSWER

While some acid-base reactions can be endothermic, most are exothermic, meaning they release heat. Therefore, it is misleading to state that the solution becomes much cooler; rather, it typically heats up as the reaction proceeds.

C (There is usually an explosion.) YOUR ANSWER

Explosions are not a common outcome of acid-base reactions in aqueous solutions. Although violent reactions can occur under specific conditions (such as with concentrated acids or bases), most acid-base neutralizations are controlled and do not result in explosions.

D (A large amount of solid material always forms.) YOUR ANSWER

The formation of solid material is not a guaranteed outcome in acid-base reactions. While some reactions may produce precipitates, many do not, especially when a strong acid reacts with a strong base. Thus, this statement does not apply universally to all acid-base interactions.

Conclusion

In summary, when an acid is added to a base in water, the primary and consistent result is a change in pH due to the neutralization reaction. Other choices either misrepresent typical outcomes or apply only under specific circumstances, making option A the most accurate reflection of the process involved. Understanding these reactions is crucial in fields such as chemistry and environmental science, where pH plays a vital role in various applications.

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