Write down the Ksp expression for CaF2. If the molar solubility of CaF2 at 35℃ is 1.24×10^(-3)mol/dm3, calculate the value of Ksp.
CaF2(s) ==> Ca^+2 + 2F^-
Ksp = (Ca^+2)(F^-)^2.
Set up an ICE chart and solve.
The solubility product constant (Ksp) expresses the equilibrium constant for the dissolution of an ionic compound in a solvent. To write the Ksp expression for CaF2, we need to start with the balanced equation for the dissolution process:
CaF2 (s) ⇌ Ca2+ (aq) + 2 F- (aq)
The brackets "(aq)" denote that the ions are in the aqueous phase and the "(s)" denotes the solid state. Since the balanced equation indicates that you get one Ca2+ ion and two F- ions for every formula unit of CaF2 that dissolves, we can write the Ksp expression as:
Ksp = [Ca2+][F-]^2
Now, to calculate the value of Ksp, we need to use the molar solubility of CaF2. The molar solubility represents the number of moles of CaF2 that can dissolve in one liter (dm3) of water. In this case, the molar solubility is given as 1.24×10^(-3) mol/dm3.
Since CaF2 dissociates into one Ca2+ ion and two F- ions, the molar solubility of Ca2+ and F- ions is also 1.24×10^(-3) mol/dm3.
Substituting these values into the Ksp expression, we get:
Ksp = (1.24×10^(-3) mol/dm3) * [(1.24×10^(-3) mol/dm3)]^2
Ksp = 1.917×10^(-10) mol^3/dm^9
Therefore, the value of Ksp for CaF2 at 35℃ is 1.917×10^(-10) mol^3/dm^9.