Solutions of CuCO3

Question

What is minimum volume of distilled water that is needed to completely dissolve a 3.0g sample of CuCO3 at 25 degrees C? (Ksp for CuCO3 is 2.5x10^-10 at 25 degrees C)

Answer 1

First, use the Ksp to calculate the molar solubility of CuCO₃.

CuCO₃(s) <==> Cu²⁺(aq) + CO₃^2-(aq)

Ksp = 2.5x10^-10 = [Cu²⁺][CO₃^2-]

2.5x10^-10 = (x)(x) = x²

x = 1.58x10^-5 M = molar solubility of CuCO₃

Next we find how many moles of CuCO₃ is contained in 3.0 g, using a molar mass of 123.6 g/mol

3.00 g x 1 mol/123.6 g = 0.0243 moles

Finally, we calculate volume of water to dissolve 0.0243 moles to give a concentration of 1.58x10^-5 M:

0.0243 mol / x L = 1.58x10^-5 mol/L

x = 1.5x10³ L of water (2 sig.figs.) needed to dissolve 3.0 g of CuCO₃