Question

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, when the other cation just begins to precipitate? (ANSWER IS NOT .021 or 2.0E-6)

Answer #1

**Part
A**

Fe^{2+} will precipitate first as solubility product of
FeCO_{3} is lower than solubility product of
MgCO_{3}.

**Part
B**

FeCO_{3}
Fe^{2+} + CO_{3}^{2-}

K_{sp} = [Fe^{2+}][CO_{3}^{2-}] =
3.07 x 10^{-11}

3.07 x 10^{-11} = (2.1 x
10^{-2})[CO_{3}^{2-}]

[CO_{3}^{2-}] = 1.5 x 10^{-9} M to
precipitate the Fe^{2+} ions

**Part
C**

MgCO_{3}
Mg^{2+} + CO_{3}^{2-}

K_{sp} = [Mg^{2+}][CO_{3}^{2-}] =
3.07 x 10^{-11}

6.82 x 10^{-6} = (1.6 x
10^{-2})[CO_{3}^{2-}]

[CO_{3}^{2-}] = 4.3 x 10^{-4} M to
precipitate the Mg^{2+} ions

K_{sp} = [Fe^{2+}][CO_{3}^{2-}]
= 3.07 x 10^{-11}

3.07 x 10^{-11} = [Fe^{2+}](4.3 x
10^{-4})

[Fe^{2+}] = 7.1 x 10^{-8} M when the
Mg^{2+} ions precipitates

Consider a solution that is 2.5×10−2 M in Fe2+and
1.0×10−2 M in Mg2+.
What is the remaining concentration of the cation that
precipitates first, when the other cation just begins to
precipitate?

A solution of NaF is added dropwise to a solution that is 0.0532
M in Mg2+ and 1.43e-05 M in Y3+.
The Ksp of MgF2 is 5.16e-11.
The Ksp of YF3 is 8.62e-21.
(a) What concentration of F- is necessary to begin
precipitation? (Neglect volume changes.)
[F-] = M.
(b) Which cation precipitates first?
Mg2+Y3+
(c) What is the concentration of F- when the second
cation begins to precipitate?
[F-] = M.

A solution contains 5.84×10-3 M
potassium fluoride and
5.84×10-3 M ammonium
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Solid magnesium nitrate is added slowly to this
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A. What is the formula of the
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formula =
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A solution contains 1.43×10-2 M
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Solid manganese(II) acetate is added slowly to
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A) What is the formula of the substance that
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B) What is the concentration of
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Given: Ksp(Ag2CrO4) = 1.2×10-12 Ksp(BaCrO4) = 2.1×10-10
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Ag+, it is desired to precipitate one of these ions as its chromate
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Consider the reaction
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at 79 ∘C , where [Fe2+]= 3.30 M and [Mg2+]= 0.310
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Part A
What is the value for the reaction quotient, Q, for the
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Part B
What is the value for the temperature, T, in
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Express your answer to three significant figures and include the
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Part C
What is the value for n?
Express your answer as an integer and include the appropriate
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Part A:What is the value for the reaction quotient, Q,
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Express your answer numerically.
Part B:What is the value for the temperature, T, in
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Express your answer to three significant figures and
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formula =
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show work

A solution contains 9.78×10-3 M
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Solid ammonium carbonate is added slowly to this
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