Solving for x in calculating pH questions

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Miya Eberlein 1J
Posts: 29
Joined: Fri Sep 25, 2015 3:00 am

Solving for x in calculating pH questions

Postby Miya Eberlein 1J » Sun Nov 29, 2015 10:40 pm

Why do we sometimes ignore the x in the denominator of the ratio of concentrations and sometimes we keep it there, for when we are solving for x in the questions that ask to find the pH?

Neel Patel - 2A
Posts: 48
Joined: Fri Sep 25, 2015 3:00 am

Re: Solving for x in calculating pH questions

Postby Neel Patel - 2A » Sun Nov 29, 2015 11:08 pm

If the Ka or the Kb, depending what type of reaction you are working on is really small then the x on the bottom of the denominator is generally ignored because when rounded the final answer is not really affected by the change in x. The x is going to be so small that the equilibrium concentration is not going to be affected.

Roy Hsieh 1C
Posts: 9
Joined: Fri Sep 25, 2015 3:00 am

Re: Solving for x in calculating pH questions

Postby Roy Hsieh 1C » Sun Nov 29, 2015 11:12 pm

X can be calculated regardless, but in cases where it's so small, it can be ignored to save time. I personally would try to solve as if x is there, but that is only if I have the time to try.


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