Question

Suppose you are studying the Ksp of CaCl2, which has a molar mass of 110.98 g/mol, at multiple temperatures. You dissolve 4.99 g of CaCl2 in 10.0 mL of water at 100 oC and cool the solution. At 90 oC, a solid begins to appear. What is the Ksp of CaCl2 at 90 oC

Answer 1

Hence the Solubility product,

Ksp = [Ca2+] [Cl-]2

or, Ksp = (4.5) (9)2

or, Ksp = 364.5

Step-by-step explanation:

Mass of CaCl2 = 4.99 g

Molar mass of CaCl2 = 110.98 g/mol

Moles of CaCl2

= given mass/ molar mass

= 4.99/ 110.98

= 0.045

Volume = 10.0 mL = 0.01 L

CaCl2 dissociates into its ion as:

CaCl2 (s) \rightleftharpoons Ca2+ (aq) + 2 Cl- (aq)

At 90°C, the solution is saturated with Ca2+ and Cl- ions.

Moles of Ca2+ = Moles of CaCl2 dissolved = 0.045

Moles of Cl- = 2 x ( Moles of CaCl2 dissolved) = 2 x 0.045 = 0.09

[Ca2+] = Moles/ Volume = 0.045/ 0.01 = 4.5 M

[Cl-] = 0.09/ 0.01 = 9 M

Solubility product,

Ksp = [Ca2+] [Cl-]2

or, Ksp = (4.5) (9)2

or, Ksp = 364.5