A student measures the solubility of PbI2 in pure water and in 0.10 M KI by saturating each solvent at 25 C and titrating the I- in the saturated supernatant. In pure water, [I-] = 2.6e-3 M at saturation. In 0.10 M KI, the additional I- from PbI2 dissolution is negligible, and [Pb^2+] is found to be 7.9e-7 M.
By what factor is the molar solubility of PbI2 reduced when going from pure water to 0.10 M KI?
- A
About 130-fold higher
- B
About 10-fold lower
- Ccheck_circle
About 1700-fold lower
- D
Unchanged
Explanation
Solubility (= [Pb^2+]) drops from 1.3e-3 in pure water to 7.9e-7 in 0.10 M KI. Ratio = 1.3e-3 / 7.9e-7 ~ 1.6e3.