Page 46 - ASAM BASA

Contoh 2. Calculate the pH of (a) a 1.0 x 10 M HCI salutation and (b) a 0.020 M
-3
Ba (OH) 2 solution.

Solution
(a) Since HCI is a strong acid, it is completely ionized in solution:
+
-
HCI (aq)  H (aq) + CI (aq)
The concentration of all the species (HCI, H , and CI ) before and after ionization
+
-
can be represented as follows:
+
-
HCI (aq)  H (aq) + CI (aq)
Initial (M): 1.0 x 10 0.0 0.0
-3
Change (M): -1.0 x 10 +1.0 x 10. -3 + 1.0 x 10 -3
-3
-3
Final (M): 0.0 1.0 x 10 1.0 x 10 -3

A positive (+) change represents an increase and a negative (-) change indicates a
decrease in concentrations. Thus
[H ] = 1.0 x 10 M
-3
+
pH= -log (1.0 x 10 -3
= 3.00
-
(b) Ba (OH) 2 is a strong base : each Ba (OH) 2 unit proceduces two OH ins:
-
Ba(OH) 2(aq)  Ba (aq) + 2 OH (aq)
2+

46