The solubility of barium hydroxide (in grams per litre of aqueous solution at va
ID: 474682 • Letter: T
Question
The solubility of barium hydroxide (in grams per litre of aqueous solution at various temperature is tabulated below.) (a) What saturated of barium hydroxide would be dissolved in 250 mL of a saturated solution at 60 degree C? b) Calculate the molar concentration of the solution in (a). c) If the solution in (a) was cooled to 20 degree C calculate the mass of crystals that would be produced. d) Calculate the molar concentration of hydroxide ions present in the solution in (c) at 20 degree C after the crystals were removed. e) Calculate the pH of the solution in at 20 degree C after the crystals were removed.Explanation / Answer
a) At 60 deg C, 209.4 g are dissolved at 1 L,
the amount of Ba(OH)2 dissolved in 250 mL = (209.4 g) * 250 mL / 1000 mL = 52.35 g
b) The number of mols of Ba(OH)2 = 52.35 g / 171.34 g/mol = 0.3055 mol
Thus, Molarity of Ba(OH)2 = 0.3055 mol / 0.250 L = 1.22 M
c) At 20 deg C the solubility of Ba(OH)2 is 38.9 g/L, hence the amount of Ba(OH)2 in 250 mL solution at the given temperature = (38.9 g / 1000 mL)*250 mL = 9.725 g
Thus, the amount of Ba(OH)2 is crystalized = 52.35 g - 9.725 g = 42.325 g
d) The number of mols of Ba(OH)2 at 20 deg C = 9.725 g / 171.34 g/mol = 0.0567 mol
The concentration of OH- = 0.0567*2 = 0.1135 mol
Thus, [OH-] = 0.1135 mol / 0.250 L = 0.454 M
e) pOH = - log[OH-] = -log(0.454) = 0.342
pH = 14 - 0.342 = 13.65