A ) Cu(NO 3 ) 2 is added to a solution that is 0.10 M in each of these ions: CO
ID: 901486 • Letter: A
Question
A)
Cu(NO3)2 is added to a solution that is 0.10 M in each of these ions: CO32-, CrO42–, and S2–. Which will precipitate first?
CuCO3
CuCrO4
CuS
B)
How many moles of sodium sulfate, Na2SO4, would need to be added to 1.0 L of 0.073M silver nitrate, AgNO3, to cause silver sulfate, Ag2SO4, to precipitate. The Ksp of Ag2SO4 is 1.4x10-5.
To enter your answer in scientific notation, use E for x10. Example: 1.0x10-3 would be 1.0E-3
C)
Which of these is NOT an example of a complex ion?
H2PO4-
Ag(NH3)22+
Zn(OH)42-
FeNCS2+
D)
In a qualitative analysis experiment, which of these aqueous ions will form an insoluble sulfide when H2S in base is added to the solution?
Ni2+
Ag+
Ca2+
Ba2+
a.CuCO3
b.CuCrO4
c.CuS
Explanation / Answer
A) Ksp for CuCO3 = 1.3 x 10^-10
Ksp for CuCrO4 = 3.6 x 10^-6
Ksp for CuS = 10^-36
We see that Ksp for CuS is least. Hence it will precipitate first. C) CuS
B)
Ksp of Ag2SO4 = 1.4x10-5
Ag2SO4 -----> 2Ag+ + SO42-
.......................0.073........S
Ksp = 1.4 x 10^-5 = (0.073)^2 x S
=> S = 2.63 x 10^-3 M = [SO4 2-]
Volume = 1 L
=> Moles of SO4 2- = 2.63 x 10^-3 x 1 = 2.63 x 10^-3 moles
=> Moles of Na2SO4 needed = 2.63E-3
C)
A) H2PO4- is not a complex ion since it has no metal at its centre
D)
b) Ag+ will form an insoluble sulfide
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