Acids, Bases and Salts AP 1987 a. hydroxide ion concentration = 1.64 X 10-3M and the percent dissociation = 1.09% b. pH= 8.732 c. Q=2.12 X 10-5 which is greater than the value of the Ksp which is 1.5 X 10-11, so YESa precipitate does occur.
AP 1989 a. The molecular weight of ascorbic acid is 176.1 g/mol b. Ka = 7.73 X 10-5 c. Kh=Kb=1.294X 10-10 d. pH at the equivalence point = 8.536 AP 1994 a. The Ksp expression is Ksp = [Mg+2][F-] 2 and the value of Ksp=7.09 X 10-9 b. The equilibrium concentration of Mg+2 with KF added is 7.09 X 10-7 M c. Q=1.77 X 10-9 which is less than the Ksp= 7.09 X 10-9, so NO precipitate occurs. d. The dissolving of MgF2 in water is exothermic. As the temperature increases from 18 to 27 degrees Celsius, the Mg+2 concentration lowers so according to Le Chatlierâ€™s principle, the equilibrium shifts to the left creating more solid magnesium fluoride . Molar solubility at 18 degrees = 1.21 X 10-3 M, at 27 degrees= 1.17 X 10-3 M. If the reaction were endothermic the concentration of Mg+2 would increase with increase in temperature.