please show work after stry 142 r Exam3 25 M mmol OH added mmol acetate made -mm

Question

please show work

after stry 142 r Exam3 25 M mmol OH added mmol acetate made -mm nter, 2006 are 1 acid initial acid used (10.00x0.200 nitial + salt made (1o 10.0 ml. of 0.100 M Pb+2 are added to 10.0 mL of 0.100 M SO42 1. Will PbsO, precipitate? 2. What are the equilibrium concentrations of Pb 2 and SO,2 after the precipitation reaction has occurred? Enough solid NaCl is added to make the solution 0.100 M in CIl. Will PbCl2 precipitate? 3. Enough Na CrOs is added to a fresh sample of saturated PbSO4 solution to make the system 0.100 M in CrO42. Will PbCrO4 precipitate? 4.

Explanation / Answer

Q1

if Q > Ksp, there is preciptiate

[Pb+2] = M1*V1/(V1+V2) = 0.1*10 /(10+10) = 0.05

[SO4-2] =  M2*V2/(V1+V2) = 0.1*10 /(10+10) = 0.05

Q = 0.05*0.05 = 0.0025

Ksp for PbSO4 = 2.53*10^-8

Q >> KSp

expect PbSO4(s) formation

Q2

in equilbirium

Ksp = [Pb+2][SO4-2]

2.53*10^-8 = S*s

S= sqrt(2.53*10^-8) = 0.0001590 M

Q3

if Cl- is added, then PbCl2 can form, verify this

PbCl2 <-> Pb2+ + 2Cl-

Ksp = [Pb2+][Cl-]

1.7*10^-5 = [Pb+2] *(0.1)^2

[PB+2] = (1.7*10^-5)/(0.1^2) = 0.0017

compare with [Pb+2] = 0.0017

since Pb2+ is more than Pb2+ reuqired, expect --> precipitation

Q4

True, since Pb2+ ions arestill present

Ksp = 3*10^-13

clearly, there will be precipitate, since

Ksp = [Pb2+][CrO4-2]

3*10^-13 = [Pb+2] *(0.1)

[PB+2] =(3*10^-13) /0.1 = 3*10^-12

compare with [Pb+2] = 0.0001590 = 1.59*10^-4

there will be precipitation

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