Question

Given: Ksp(Ag2CrO4) = 1.2×10^-12 Ksp(BaCrO4) = 2.1×10^-10 For a solution which is initially 0.004 M in Ba2+ and 0.004 M in Ag+, it is desired to precipitate one of these ions as its chromate (CrO42−) salt to the maximum possible degree without precipitating any of the other cation. From this solution, which ion can be selectively first-precipitated by controlled addition of CrO42− and, ideally, what is the maximum possible percentage of that ion which can be exclusively so precipitated?

Answer #1

Calculate the CrO_{4}2− ion concentration when
BaCrO_{4} first begins to precipitate

Ksp = [Ba^{2+}] [CrO_{4}2¯]

2.1×10^-10 = (0.004) [CrO_{4}2¯]

[CrO_{4}2¯] = 2.1×10^-10 / (0.004)

[CrO_{4}2¯] = **5.25 x 10^-8**

Calculate the CrO_{4}2− ion concentration when
Ag_{2}CrO4 first begins to precipitate

Ksp = [Ag^{+}]^{2} [CrO_{4}2¯]

1.2 ×10^-12 = (0.004)^2 [CrO_{4}2¯]

[CrO_{4}2¯] = 1.2 ×10^-12 / (0.004)^2

[CrO_{4}2¯] = **7.5 x 10^-8**

BaCrO_{4} precipitates first, because CrO_{4}2¯
concentration necessary to form BaCrO_{4} is smaller.

Calculate the [Ba^{2+}] ion when Ag_{2}CrO4
first begins to precipitate

Ksp = [Ba^{2+}] [CrO_{4}2¯]

2.1×10^-10 = [Ba^{2+}][7.5 x 10^-8]

[Ba^{2+}] = 2.1×10^-10 /7.5 x 10^-8

[Ba^{2+}] = **2**.**8 x
10^-3**

Calculate the percent Ba^{2+} remaining in solution:

(2.8 x 10^-3)/ (0.004) x 100 = 70%

The maximum possible percentage of Ba^{2+} ion which can
be exclusively precipitated

= 100 – 70 = **30%**

Selective Precipitation
Given: Ksp(Ag2CrO4) = 1.2×10-12 Ksp(BaCrO4) = 2.1×10-10
For a solution which is initially 0.003 M in Ba2+ and 0.003 M in
Ag+, it is desired to precipitate one of these ions as its chromate
(CrO42−) salt to the maximum possible degree without precipitating
any of the other cation. From this solution, which ion can be
selectively first-precipitated by controlled addition of CrO42−
and, ideally, what is the maximum possible percentage of that ion
which can be exclusively so...

A solution contains 0.010 M Ba2+ and 0.010 M Ag+. Can 99.91% of
either ion be precipitated by
chromate (CrO42-) without precipitating the other metal ion? The
Ksp for BaCrO4 is 2.1 x 10-10 and
the Ksp for Ag2CrO4 is 1.2 x 10-12

A solution contains 0.010 M Ba2+ and 0.010 M
Ag+. If we add chromate (CrO42-)
to the solution:
Which ion starts to precipitate first?
Can 99.90% of either ion be precipitated by chromate without
precipitating the other metal ion?
pKsp BaCrO4 = 9.67,
pKsp Ag2CrO4=11.92

A solution containing a mixture of 0.0444 M potassium chromate
(K2CrO4) and 0.0664 M sodium oxalate (Na2C2O4) was titrated with a
solution of barium chloride (BaCl2) for the purpose of separating
CrO42– and C2O42– by precipitation with the Ba2 cation. Answer the
following questions regarding this system. The solubility product
constants (Ksp) for BaCrO4 and BaC2O4 are 2.10 × 10-10 and 1.30 ×
10-6, respectively.
A.) Which barium salt will precipitate first?
B.) What concentration of Ba2+ must be present...

Silver chloride has Ksp = 1.6 x 10-10 and silver chromate has
Ksp = 9.0 x 10-12. We have 1.00 liter of a
solution which contains both NaCl (0.10 M) and Na2CrO4 (0.10 M).
Solid AgNO3 is added slowly and the solution is stirred well.
a) Which salt precipitates first, AgCl or Ag2CrO4? (Show
your work!)
b) What are the concentrations of [Ag+], [Cl-], and [CrO42-] at
the point when the second salt just begins to
precipitate?
c) Is this...

Suppose there is a solution containing 0.020 M Ba2+ and 0.020 M
Co2+. Which of them is precipitated first by addition of CO32? Is
it possible to lower the concentration of the first precipitated
ion by 99.99% without precipitating the other? (Ksp of BaCO3 = 2.58
x10^-9 and Ksp of CoCO3 = 1.00 x10-10)

Consider a solution that is 2.1×10−2 M in Fe2+ and
1.6×10−2 M in Mg2+.
Part A
If potassium carbonate is used to selectively precipitate one of
the cations while leaving the other cation in solution, which
cation will precipitate first? ANSWER: Fe 2+
Part B
What minimum concentration of K2CO3 is required to cause the
precipitation of the cation that precipitates first? ANSWER:
[K2CO3] = 1.5×10−9
M
Part C
What is the remaining concentration of the cation that
precipitates first,...

12.) An acid has a Ka = 1.0 x 10-6. At what pH would this acid
and its corresponding salt make a good buffer?
a.) 4
b.) 5
c.) 6
d.) 7
e.) not enough info is given to determine this answer.
13.) A weak acid, HA has a Ka= 1.00 x 10-3. If [HA] = 1.00 M,
what must [A-] be for the pH to be 2.70?
a.) 0.50 M b.) 2.0 M c.) 2.7 M d.) 0.37 M...

A solution contains 7.61×10-3 M
sodium chromate and
1.37×10-2 M sodium
chloride.
Solid silver nitrate is added slowly to this
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What is the concentration of chloride ion when chromate ion
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[chloride] = --------------M
Table of Solubility Product Constants (Ksp at 25
oC)
Type
Formula
Ksp
Bromides
PbBr2
6.3 × 10-6
AgBr
3.3 × 10-13
Carbonates
BaCO3
8.1 × 10-9
CaCO3
3.8 × 10-9
CoCO3
8.0 × 10-13
CuCO3
2.5 × 10-10
FeCO3
3.5 × 10-11
PbCO3...

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