Answer each of the following questions regarding BaSO 4 (Ksp = 1.1 X 10 -11 ) a)
ID: 899579 • Letter: A
Question
Answer each of the following questions regarding BaSO4 (Ksp = 1.1 X 10-11)
a) For a saturated solution of barium sulfate, what is the molar concentration of Ba2+ if activity coeffecients are ignored?
b) In which of the following solutions will barium sulfate be the most soluble and WHY: 0.25 M sodium sulfate, 0.25 M barium chloride, 0.25 M potassium nitrate
c) Sulfate ion is a weak base. Will raising the pH of the solution of saturated barium sulfate increase the molar solubility of barium sulfate or decrease the molar solubility? WHY?
Explanation / Answer
a) For a saturated solution of barium sulfate, what is the molar concentration of Ba2+ if activity coeffecients are ignored?
Solution :-
BaSO4 ------- > Ba^2+ + SO4^2-
x x
ksp = [Ba^2+][SO4^2-]
1.1*10^-11 = [x][x]
1.1*10^-11 = [x]^2
Taking square root of both sides we get
3.32*10^-6 =x
So the molar concentration of the Ba^2+ = 3.32*10^-6 M
b) In which of the following solutions will barium sulfate be the most soluble and WHY: 0.25 M sodium sulfate, 0.25 M barium chloride, 0.25 M potassium nitrate
Solution :- Barium sulfate will be more soluble in the 0.25 M potassium nitrate because it do not contain any common ion with the barium sulfate.
c) Sulfate ion is a weak base. Will raising the pH of the solution of saturated barium sulfate increase the molar solubility of barium sulfate or decrease the molar solubility? WHY?
Solution : -
Increasing pH means increasing the concentration of the OH- therefore as the pH increase then it will decrease the solubility of the BaSO4. Since BaSO4 is weakly basic means when it dissociates then it forms HSO4- and OH-
So increasing the pH causes the OH- to increase which is common ion so it will decrease the solubility of the BaSO4
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