Hey! Sign in to get help with your study questionsNew here? Join for free to post

Calculating pH of a Weak Acid

Announcements Posted on
Talking about ISA/EMPA specifics is against our guidelines - read more here 28-04-2016
  1. Offline

    ReputationRep:
    Could somebody please answer this question for me and show me your working so I can hopefully see how it's done? I'm fine with strong acids that completely ionise but I'm struggling with weak acids.



    Calculate the pH of 0.01 mol.dm-3 propanoic acid (a weak acid, which partially ionises and has a dissociation constant of 1.34 x 10-5 mol.dm-3) at 298K.
  2. Offline

    ReputationRep:
    (Original post by TFish89)
    Could somebody please answer this question for me and show me your working so I can hopefully see how it's done? I'm fine with strong acids that completely ionise but I'm struggling with weak acids.

    Calculate the pH of 0.01 mol.dm-3 propanoic acid (a weak acid, which partially ionises and has a dissociation constant of 1.34 x 10-5 mol.dm-3) at 298K.
    Do you know the formula for the dissociation of a weak acid?

    ka = [H+][A-]/[HA]

    assume [HA] is constant
  3. Offline

    ReputationRep:
    (Original post by charco)
    Do you know the formula for the dissociation of a weak acid?

    ka = [H+][A-]/[HA]

    assume [HA] is constant
    This plus the fact that [H+]=[A-]

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. Oops, you need to agree to our Ts&Cs to register
  2. Slide to join now Processing…

Updated: June 28, 2012
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

Today on TSR

How to predict exam questions

No crystal ball required

Poll
How will you be voting in the EU referendum?
Quick reply
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.