[norwegiandude]

Ok, we are basically saying the same thing here, because the last equation you wrote there, is the one I'm staring at my paper at this moment, which gave me pH 2,948. We must be using more/less decimals than the other .

And on a), it really looks like my first answer, which made me question this whole problem in general. But thank you for the final input!

EDIT: When i solved the equation, i got x= 1,127 * 10^-3, using all the decimals i get on my calculator

[Borek]

[itex]\to [H^+]  = 0.00111889...     ,  pH = 2,95121... > 2,948 [/itex]  it differs, beyond any error of rounding

There are several things that can yield a different result: 0.089 M is not an exact concentration, it is already rounded, and the accurate value depends onmolar mass of KOH used (typically 56 vs 56.11). pKa value - sometimes given as 4.74, sometimes as 4.75, sometimes as 4.76 (plus some other values with more significant digits), not clear to me which value norwegiandude used. As it was never clarified which values are used, there is not much sense in comparing 4^th digits.

[norwegiandude]

I may not have been as accurate as you on the molar mass, now that you mention it, but i will round to 2,95 in my answer, so the difference will be shown. But thanks for the added info, I dont mind getting constructive advice . Thanks to you both!