Solid sodium carbonate is slowly added to 75.0 mL of a 0.0611 M lead acetate solution. The concentration of carbonate ion required to just initiate precipitation is

Question

Solid sodium carbonate is slowly added to 75.0 mL of a 0.0611 M lead acetate solution. The concentration of carbonate ion required to just initiate precipitation is _____ M.

Answer 1

First, identify the precipitate....

Na₂CO₃(s) + Pb(Ac)₂(aq) ===> 2NaAc(aq) + PbCO₃(s) So, PbCO3 is the precipitate of the reaction.

Look up the Ksp for PbCO3. I find a value of 1.5x10^-13

Ksp = [Pb²⁺][CO₃^2-]

We can find the [Pb2+] from the information provided: [Pb²⁺] = 0.0611 M

Now, we can solve for [CO₃^2-]:

1.5x10^-13 = [0.0611][CO₃^2-]

[CO₃^2-] = 2.45x10^-12 M to just initiate precipitation