Question

Calculate the ph of the solution made by adding 0.50 mol of hobr and 0.30 mol of kobr to 1.00 l of water. the value of ka for hobr is 2.0×10?9.

Answer 1

To fully understand the problem, we use the ICE table to identify the concentration of the species. We calculate as follows:

Ka = 2.0 x 10^-9 = [H+][OBr-] / [HOBr]

HOBr = 0.50 M
KOBr = 0.30 M = OBr-

HOBr + H2O <-> H+ + OBr-
I 0.50 - 0 0.30
C -x x x
---------------------------------------------
E(0.50-x) x (0.30+x)

Assuming that the value of x is small as compared to 0.30 and 0.50

Ka = 2.0 x 10^-9 = x (0.30) / 0.50)

x = 3.33 x 10^-9 = H+
pH = 8.48