Chemical Forums

Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: KaczuH on May 21, 2013, 12:28:52 PM

Title: pH calculations using Kso
Post by: KaczuH on May 21, 2013, 12:28:52 PM

Could someone explain to me why this solution doesn't work? Why I have to use ICE method?

Calculate pH of saturated Mg(OH)₂ solution K_so=1.1*10^-11

(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fs8.postimg.org%2Fl43z5fk39%2FKso.gif&hash=276a2f6290b2028c839e9b2358d1f04fb1145c6e)

Title: Re: pH calculations using Kso
Post by: Borek on May 21, 2013, 01:56:01 PM

What about OH^- from water autodissociation?

For Mg(OH)₂ your approach is OK, it would be problematic for less soluble hydroxides.

Title: Re: pH calculations using Kso
Post by: KaczuH on May 21, 2013, 03:09:45 PM

Quote from: Borek on May 21, 2013, 01:56:01 PM

What about OH^- from water autodissociation?

This is what i've missed. Everything is correct now. The difference between both results  is approximately 0.2. Thanks!