Question

For each of the salts on the left, match the salts on the right that can be compared directly, using K_sp values, to estimate solubilities.

(If more than one salt on the right can be directly compared, include all the relevant salts by writing your answer as a string of characters without punctuation, e.g, ABC.)

	1.	iron(III) sulfide		A. CaCO3
	2.	manganese(II) carbonate		B. Ba3(PO4)2
				C. Zn3(PO4)2
				D. Co(OH)2

Write the expression for K in terms of the solubility, s, for each salt, when dissolved in water.

iron(III) sulfide			manganese(II) carbonate
Ksp =			Ksp =

Note: Multiply out any number and put it first in the K_sp expression. Combine all exponents for s.

Answer 1

1) iron(III) sulfide = Fe₂S₃ ---------> 2 Fe³⁺ + 3S^2-

Ksp = (2s)² (3s)³ = 108 s⁵

B. Ba3(PO4)2 ---------->  3 Ba2⁺ + 2PO₄^3-

  Ksp = (3s)³ (2s)2 = 108 s⁵

C:

Zn3(PO4)2 ---------->  3 Zn2⁺ + 2PO₄3-

  Ksp = (3s)³ (2s)² = 108 s⁵

2) manganese(II) carbonate

   MnCO3 ---------> Mn²⁺ + CO₃2-

  Ksp = s.s = s²

A: CaCO3 ---------> Ca²⁺ + CO₃^2-

  Ksp = s.s = s²

3) iron(III) sulfide

Fe₂S₃ ---------> 2 Fe³⁺ + 3S^2-

Ksp = (2s)² (3s)³ = 108 s⁵

manganese(II) carbonate

   MnCO3 ---------> Mn²⁺ + CO₃^2-

  Ksp = s.s = s²