An acid solution of pH equal to three is gradually diluted with water.

An acid solution of pH equal to three is gradually diluted with water. As a result of this dilution, the pH of the solution will

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reach near to zero.

reach near to fourteen.

reach near to seven.

remain unchanged.

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Answer is Wrong!

This question was previously asked in

UPSC CISF-AC-EXE – 2018

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An acid solution with pH = 3 has a relatively high concentration of H+ ions. Diluting this solution with pure water (which has a neutral pH of 7) reduces the concentration of the acid, and thus the concentration of H+ ions from the acid. The total concentration of H+ ions approaches the concentration of H+ ions in pure water (which is $10^{-7}$ M at 25°C, corresponding to pH 7). As the concentration of H+ decreases, the pH value (which is -log[H+]) increases. The pH will move from 3 towards 7, but it will not exceed 7 when diluting with pure water.

Diluting an acidic solution with neutral water increases its pH, moving it towards 7.

Similarly, diluting a basic solution with neutral water decreases its pH, moving it towards 7. The pH of a solution being diluted with pure water will approach the pH of pure water (7), but will not cross the neutrality point unless the original solution was extremely concentrated or involved complex acid-base equilibria not typical for this type of question.

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