Question

(Part A) The concentration of barium carbonate in a saturated aqueous solution of the salt at 25°C is 7.07 x 10^-6  M. What is the K_sp of this sparingly soluble salt?

(Part B)   After mixing an excess PbCl₂ with a fixed amount of water, it is found that the equilibrium concentration of Pb²⁺ is 1.6 × 10^–2M.  What is K_sp for PbCl₂?

Answer 1

Part A

BaCO3(s) ------> Ba2+(aq) + CO3^2-(aq)

Ksp = [ Ba2+ ] [ CO3^2-]

Concantration of BaCO3 = 7.07×10^-6M

Concentration of Ba2+ = 7.07×10^-6M

Concentration of CO3^2- = 7.07 ×10^-6M

Therefore,

Ksp = 7.07 ×10^-6 × 7.07 ×10^-6

= 5.00 × 10^-11

Part B

PbCl2(s) <----> Pb2+(aq) + 2Cl-(aq)

Ksp =[ Pb2+] [ Cl- ]^2

Concentration of Pb2+ = 1.6×10^-2M

Concentration of Cl- = 2 × Concentration of Pb2+

= 2 × 1.6 × 10^-2M = 3.2×10^-2M

Therefore,

Ksp = 1.6×10^-2 × ( 3.2 ×10^-2)^2

= 1.64 × 10^-5