Question

1) find the hydronium ion concentration, the hydroxide ion concentration and the pH of a 0.000001 M solution of NaOH.
2) which of salts hydrolyze in aqueous solution : (NH4)2S, Na2So3,(CH3COO)2Ca?
Write the ionic equationss for the hydrolysis reacrions. Predict the pH of solution (pH=7 , pH>7 , ph<7) ?

Answer 1

The tendency for students is to say that the (OH^-) is 1E-6M but this is only 10 times more than is in H2O when it ionizes; therefore, we must add that in to the mixture. Here is how you do it.

NaOH is a strong electrolyte; therefore it will ionize 100% as follows.
..................NaOH --> Na^+ + OH^-
I.................1E-6..........0...........0
C..............-1E-6.........1E-6.....1E-6
E..................0............1E-6.....1E-6

Then add this to the ionization of water.
...............H2O ==> H^+ + OH^-
I..............liquid.......0........1E-6
C............liquid.......x...........x
E............liquid.......x.........1E-6+x

Kw = (H^+)(OH^-) = 1E-14
(x)(1E-6 + x) = 1E-14
Solve for x = (H^+), evaluate 1E-6+x for OH^- and convert all to pH.

For 2, look on Google and see what you can do for yourself.

Answer 2

Thank you very much!