Question

A solution of 0.31 M Pb(NO3)2 and 0.27 M AgNO3 is formed. What will precipitate first if solid KCl is added?

(Ksp of PbCl2 = 1.6 x 10-5 and Ksp of AgCl = 1.8 x 10-10)
A. KNO3
B. AgCl
C. PbCl2
D. AgNO3

Answer 1

Upon addition of KCl to a solution of 0.31 M Pb(NO₃)₂ and 0.27 M AgNO₃, AgCl, with a Ksp of 1.8 x 10⁻¹⁰, will precipitate first due to its lower solubility compared to PbCl₂ with a Ksp of 1.6 x 10-5.

Step-by-step explanation:

When solid KCl is added to a solution of 0.31 M Pb(NO₃)₂ and 0.27 M AgNO₃, we must evaluate which insoluble chloride salt will precipitate first. The precipitation of a salt from a solution is governed by the solubility product constant (Ksp) and the reaction quotient (Q).

Here, we compare the Ksp values of PbCl2 and AgCl to decide which will precipitate first upon addition of KCl. The Ksp for PbCl₂ is 1.6 x 10⁻⁵ and for AgCl, it is 1.8 x 10⁻¹⁰. Since a smaller Ksp indicates a lower solubility, AgCl, with its much smaller Ksp, will reach its saturation point and precipitate out of the solution before PbCl₂ does upon addition of KCl. Therefore, the answer is B. AgCl.