Concept:Adding a strong acid, such as concentrated
HCl, increases the concentration of hydrogen ions
[H+] in the solution.
Explanation:The pH of a solution is defined as
pH=−log10[H+].
A lower pH value corresponds to a higher hydrogen ion concentration and therefore a more acidic solution.
The original solution has a pH of
3.4, which is already acidic.
When a few drops of concentrated
HCl are added, the
HCl dissociates completely as
HCl→H++Cl−.
This increases the total
[H+] in the mixture.
Because
[H+] increases, the pH must decrease from
3.4 to a value lower than
3.4.
Hence, the resulting mixture becomes more acidic than the original solution.
Answer:The pH of the resulting mixture is less than
3.4.
Correct option: A. less than 3.4.