Solid lead(II) fluoride, PbF2, is sparingly soluble in water. The solubility‐product constant at 25 °C is Ksp=4.0×10−8. A chemist investigates how the presence of fluoride ion affects the extent to which PbF2 dissolves.
Answer the following questions. Show all reasoning, state any assumptions, and report all answers with appropriate units and significant figures.
(a) Write the balanced dissolution equilibrium for PbF2 in water and the corresponding Ksp expression.
(b) Calculate the molar solubility of PbF2 in pure water at 25 °C.
(c) A solution is prepared that is 0.100 M in NaF. Calculate the molar solubility of PbF2 in this fluoride solution. Explicitly verify whether any algebraic approximation used in your calculation is justified.
(d) Express the solubility obtained in part (c) as the mass (in g) of PbF2 that can dissolve per liter of the 0.100 M NaF solution.