It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. I know that diluting an acid causes it to dissociate to a greater extent.
But at the same time, you would be diluting its conjugate base and causing it to associate more, cancelling the dissociation of the acid. In addition to the above reason, pH will always approach 7 at extreme dilution as it approaches being pure water.
I did the experiment. My buffer was a commercial product a simple packet of salts probably phthalate based. I rinsed the probe with deionised water between readings. The pH fell from 4 to 3.
See the table below. I was not expecting this. The change appears significant. I am inclined to agree that the Ka is dependent on ionic strength and to a greater level than I previously thought. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. We have to be careful here to watch out for the conditions. It is important to note whether the total volume of the buffer changed.
Why is this important? Firstly, if the volume changed drastically, i. Which is the pH of water. Second, if the total volume remained constant , it means that dilution AND removal of some of the solution had happened. Note that since some of the solution was removed, the number of moles of salt and acid decreased. So when a small amount of strong acid is added, say 0. After dilution: ratio becomes 0.
First, let's calculate the moles of HCl aq in our stock solution using the relationship:. HCl aq is a strong acid , so it fully dissociates. This tells us that there are 0.
Now imagine that we pour all mL of this solution into a 1. What will happen to the pH of the solution after dilution? What will be the pH of this new solution? So what's the problem? Play the game now! We added water to this stock solution, we diluted it to 1. We can use the dilution formula to calculate V f :.
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