Ishwar S. answered 05/01/21
University Professor - General and Organic Chemistry
Ba(OH)2 is a strong base, so it will ionize completely in an aqueous solution to form Barium and hydroxide ions.
Ba(OH)2 → Ba2+ + 2OH-
For 1 mole of Ba(OH)2 that ionizes, 2 moles of OH- are formed.
[OH-] = 2 x 0.206 M = 0.412 M
pOH = -log [OH-] = -log 0.412 = 0.39
pH + pOH = 14.00
pH = 14.00 - pOH = 14.00 - 0.39 = 13.61