In: Chemistry
a) A solution contains 9.54×10-3 Mlead acetate and1.38×10-2 M calcium nitrate.
Solid potassium sulfide is added slowly to this
mixture.
What is the formula of the substance that
precipitates first? Formula = ___
What is the concentration ofsulfide ion when this
precipitation first begins? [S2-] = ___
M
b) A solution contains 5.90×10-3 Msodium phosphate and1.09×10-2 M potassium
hydroxide.
Solid lead acetate is added slowly to this
mixture.
What is the formula of the substance that
precipitates first? Formula = ___
What is the concentration of leadion when this precipitation first begins?
[Pb2+] = ___ M
c) A solution contains 1.32×10-2 Mzinc acetate and6.30×10-3 M copper(II)
nitrate.
Solid sodium hydroxide is added slowly to this
mixture.
What is the formula of the substance that
precipitates first? Formula = ____
What is the concentration ofhydroxide ion when this
precipitation first begins? [OH-] = ___
M
a)
Ksp of PbS = 3.2 x 10-28
Ksp of CaS = 8 x 10-6
here PbS will precipitates first . because Ksp value is
low.
formula of the substance that precipitates first =
PbS
PbS ------------> Pb2+ + S2-
Ksp = [Pb2+ ][S2-]
3.2 x 10^-28 = 9.54 x 10^-3 x [S2-]
[S2-] = 3.35 x 10^-26 M
b)
Ksp of Pb3(PO4)2 = 3.0 x 10-44
Ksp of Pb(OH)2 = 2.8 x 10-16
formula of the substance that precipitates first = Pb3(PO4)2
Pb3(PO4)2 ----------> 3 Pb2+ + 2 PO43-
Ksp = [Pb2+]^3 [PO43-]^2
3.0 x 10-44 = [Pb2+]^3 x ( 5.90×10-3)^2
[Pb2+] = 9.52 x 10^-14 M
c)
formula of the substance that precipitates first = Cu(OH)2
[OH-] = 5.04 x 10^-9 M