[shanndog]

Hello, so here is my question =D

Given that Ka= 1.8x10^-5, what would be the effect on [H3O+] of diluting a 100mL sample of 0.4M acetic acid solution (CH3COOH(aq) to 500mL.

Im not really sure where  to even start, I thought at first it might have something to do with,    1.8x10^-5 = [H3O+][CH3COOH](aq) finding the pH to be -log(0.4) = .397
Then that goes to 1x10^.397 and divide this into the Ka??

Im really stuck with this one!
Don't do it for me! I would really enjoy working this out with some tips not really someone solving it for me

Any help is greatly appreciated thanks so much!!
Shanndog

[rabolisk]

Start from the beginning. What is the meaning of Ka of an acid? Consult your textbooks if needed.

[adianadiadi]

find the pH at two different concentrations. Use the appropriate equations. H+ is the sqrt of Ka x c.

[shanndog]

Hey,

Thanks for the reply, Ka is the equillbirum constant for partial ionization of weaker acids in water.

Ill try out the method above as well and get back to you!

Shanndog

[Borek]

H+ is the sqrt of Ka x c.

It is not. That is - sometimes it is, sometimes it is not, depending on whether specific condition is meet. Using this formula blindly will get you nowhere.

http://www.chembuddy.com/?left=pH-calculation&right=pH-weak-acid-base

[shanndog]

Hi,

Yes I didnt get anywhere with the equation =S!

However I am still a bit stuck =(.

Shanndog