Question

Question 21 pts

Determine if a precipitate will form when equal volumes of 4.72 x 10-5 M HCl and 4.85 x10-7 M AgNO3 are mixed to produce AgCl. Ksp AgCl = 1.6 x10-10. Determine the value of Q and report it as a -log value. If -logQ <9.796 a precipitate will form.

Answer 1

For AgCl to form

Q > Ksp

so

Q = [Ag+][Cl-]

Ksp = 1.6*10^-10

so...

get Ag+ and CL-

[Ag+] = mol of Ag+ / Total V = M1*V1 / (V1+V2) = (4.72*10^-5)*V1 / (2V1) = 0.0000236 M ( it is halved, since volumes are equal)

[Cl-] = mol of Cl- / total V = M2*V2/(V1+V2) = (4.85*10^-7)/2 = 2.425*10^-7 M

so...

calculate Q and compare with Ksp

Q = [Ag+][Cl-] = (0.0000236 )(2.425*10^-7)= 5.72*10^-12

now,

Q < Ksp

so do NOT expect precipitate of AgCl(s)

log(Q) = -log( 5.72*10^-12) = 11.242

since 11.242 > 9.796; there will not be precipitate