Question #854b9

1 Answer
Jul 5, 2017

K_(sp) = 3.97 * 10^(-3)Ksp=3.97103

Explanation:

Notice that the problem provides you with the molar solubility of the salt, i.e. the number of moles that can be dissolved per liter of solution in order to have a saturated solution of "AB"AB.

In your case, you know that 0.06300.0630 moles of "AB"AB can be dissolved in "1.00 L"1.00 L of water to form "1.00 L"1.00 L of saturated solution at 25^@"C"25C.

You can thus say that the molar solubility of the salt, ss, is equal to

s = "0.0630 mol L"^(-1)s=0.0630 mol L1

Now, you know that when "AB"AB is dissolved in water, the following dissociation equilibrium is established

"AB"_ ((s)) rightleftharpoons "A"_ ((Aq))^(+) + "B"_ ((aq))^(-)AB(s)A+(Aq)+B(aq)

Notice that every mole of "AB"AB that dissociates produces 11 mole of "A"A and 11 mole of "B"B, so right from the start, you can say that the saturated solution will contain

["A"] = ["B"][A]=[B]

Since you already know the molar solubility of the salt at 25^@"C"25C, i.e. the maximum number of moles of "AB"AB that dissociate to produce solvated ions, you can say that

["A"] = ["B"] = s[A]=[B]=s

which means that you have

["A"] = ["B"] = "0.0630 mol L"^(-1)[A]=[B]=0.0630 mol L1

By definition, the solubility product constant, K_(sp)Ksp, is equal to

K_(sp) = ["A"] * ["B"]Ksp=[A][B]

This means that you have--I won't add the units here

K_(sp) = 0.0630 * 0.0630 = color(darkgreen)(ul(color(black)(3.97 * 10^(-3))))

The answer is rounded to three sig figs.