[joemok]

I encountered a solubility product question in exercise book:
When excess solid Mg(OH)2 is shaken with 1.00 L of 1.00M NH4Cl solution, the resulting saturated solution has a pH of 9.0 at 298K.
The net equation of reaction is:
Mg(OH2) (s) + 2 NH4+ (aq) ------> Mg2+ (aq) +2 NH3 (aq) + 2H2O(l)
....

is it possible for changes of concentrations of NH4+ (aq) and 2 NH3 (aq) without involving change in concentration of OH- or H3O+?

[Donaldson Tan]

NO

[joemok]

I have encountered another questions:
Find the pH of a 1 M CH3COONH4 (aq) solution.

I also don't know why it can be assumed that the net change of CH3COO- and NH4+ are the same and equal to x and the following is the net equation of the system:
                  CH3COO-  + NH4+  <==> CH3COOH + NH3
eqm conc/M: 1-x             1-x                    x            x

Isn't there the hydrolysis of CH3COO- and NH4+? are the extent of hydrolysis the same?

[Borek]

http://www.chembuddy.com/?left=pH-calculation&right=pH-amphiprotic-salt

http://www.chembuddy.com/?left=pH-calculation&right=pH-salt-simplified

[joemok]

http://www.chembuddy.com/?left=pH-calculation&right=pH-amphiprotic-salt

http://www.chembuddy.com/?left=pH-calculation&right=pH-salt-simplified

Thank you very much!
I thought my teachers indeed forgot to tell us these assumptions are acceptable..