Acid dilution question

Question

an acid is added to water to make 30 mL of a solution with a pH of 6.5. If the solution is then diluted to a total volume of 300 mL, what will be the new value of the pH? ​ a) 6.5 b) between 6.5 and 7.5 c) 7.5 because the hydrogen ion concentration is reduced by a factor of 10 d) either A or B depending on what acid was used, but C is impossible ​ answer is D. can someone explain this question?

Answer 1

Hey, it depends on the strength of your acid. For example, if you are using a strong acid such as HCl adding more water will slightly affect the pH and will retain the 6.5. While using a weaker acid such as HPO3 2-, the water will act like a base and will raise the pH more near its own pH, which is 7.4. Hope this helps.