1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Titration Problem Chemistry pH

  1. Sep 10, 2013 #1
    1. The problem statement, all variables and given/known data

    Ok, so, I've been thinking about this for a while now.

    When I was doing titration back in high school, we had to put water (so that the solution would have a larger volume to work with) in the acid in which we were going to pour base from a buret.

    Now, my question is this:

    Why doesn't the water change the pH of the acid? You add more water which dilutes the concentration of H+. So, then, there is the equilibrium formula:


    Since you dilute the solution (let's assume by doubling the volume of the solution), the K changes:

    So, equilibrium constant is not the same anymore. Shouldn't this cause changes in the concentration of the acid and thereby false the titration?

    I feel there is something that doesn't click here.
  2. jcsd
  3. Sep 11, 2013 #2


    User Avatar

    Staff: Mentor

    It does.

    It also dilutes all other things present in the solution.

    No, K doesn't change. Equilibrium shifts till K has exactly the same value it had before.

    K didn't change, but even if it would, it would not change the titration result. Amount of acid (note: amount, not concentration!) is calculated from the neutralization stoichiometry, not from pH.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted