Question

ll Oy bird ble Souell Mility rire a . wor in "ommen the Sowowin with de creon the The solubility product constant for radium sulfate (Rasc.) is 4.2 x 10 10) What is the molar solubility of radium sulfate? (Rasoul Ž Rol Sou- at 25°C. 4,2x10-": [x] ] Ju. 2x18" x 16.48.10-4 11) What is the solubility of radium sulfate in g/L? 12) ir 25 mg of radium sulfate is added to 100.0 mL of distilled water at 25C, will all of the radium sulfate dissolve? 13) Which of the following would best describe what is formed in question 12 a) supersaturated solution b) saturated solution c) unsaturated solution d) all of the above e) none of the above

Answer 1

10) Let s is molar solubility.

RaSO4(s) -----> Ra++ + SO4-- , Ksp = 4.2*10^-11

s s (at equilibrium)

Ksp = [Ra++] [SO4--]

4.2*10^-11 = s * s

s^2 = 4.2*10^-11

s = 6.48*10^-6 M ......Answer

11) Molar solubility (s) = 6.48*10^-6 mol/L or M

Mass of RaSO4 = moles * molar mass = 6.48*10^-6 * 319.081 = 2.07*10^-3 g

Hence solubility in g/L = 2.07*10^-3 g/L .....Answer

12)

From question 11)

Solubility in g/L at 25° C = 2.07*10^-3 g/L OR 2.07 mg/L

Given solubility = 25 mg / 100 ml = 25mg/0.100L = 250 mg/L

250 mg/L is greater 2.07 mg/L . Thus, it will not dissolve completely. ....Answer

13)

Supersaturated solution