# How Do You Calculate Molar Solubility From Ksp?

at equilibrium :

[Pb2+] = x

[CO32-]= x + 0.02

Ksp = 7.4 x 10^-14 = [Pb2+][CO32-] = (x)(x+0.02)

x = molar solubility = 3.7 x 10^-12 M

## The Ksp of Cr(OH)2 is 6.7 E-31...help!?

Calculate its molar solubility in: a) neutral water b) in a solution buffered at pH 11 c) in a solution of .1M Cr(NO3)2 help! thanks.

Cr(OH)2(s) = Cr^2+(aq) + 2 OH^-(aq); Ksp = 2 x 10^-16

......................x.................2x

a) Ksp = [Cr^2+][OH^-]^2 = (x)(2x)^2 = 4x^3

4x^3 = 2 x 10^-16

x^3 = 5 x 10^-17

x = 3.68 x 10^-6 M This is the molar solubility of Cr(OH)2 in water

b) pH = 11. [H^+] = 10^-pH = 10^-11 = 1 x 10^-11; Kw = [H^+][OH^-] = 1 x 10^-14

[OH^-] = Kw/[H^+] = (1 x 10^-14)/(1 x 10^-11) = 1 x 10^-3 M OH^-

Ksp = [Cr^2+][OH^-]^2 = 2 x 10^-16

In this case the solubility of the Cr(OH)2 is equal to the [Cr^2+]

[Cr^2+] = Ksp/[OH^-]^2 = (2 x 10^-16)/(1 x 10^-3)^2 = 2 x 10^-10 M

molar solubility = 2 x 10^-10 M

c) 0.1M Cr(NO3)2 will give us a [Cr^2+] = 0.1M

In this case the molar solubility will be related to the [OH^-] in solution that is calculated from the Ksp equation. Remember, [Cr^2+] = [OH^-]/2 in the solubility equation.

[Cr^2+][OH^-]^2 = 2 x 10^-16

(0.1)[OH^-]^2 = 2 x 10^-16

[OH^-]^2 = 2 x 10^-15

[OH^-] = 4.5 x 10^-8 M For each Cr^2+ in solution 2 OH^- ions are produced by dissolving a Cr(OH)2 formula unit. Therefore, [Cr^2+] = [OH^-]/2 = 2.3 x 10^-8 M

molar solubility = 2.3 x 10^-8 M

## Molar solubility, calculate Ksp help?

The molar solubility of MgCO3 is 1.8 x 10^-4 mol/L. What is the Ksp for this compound? Ksp = [Mg] [CO]^3 Ksp = [1.8 x 10^-4] [3 x 1.8 x 10^-4]^3 Ksp = 2.8 x 10^-14 apparently thats not correct and the answer is actually 3.2 x 10^-8 What am I doing wrong?

You have the right idea, you just made an early mistake. First it helps if you write out the ionization equation, which is:

MgCO3 --> Mg2+ + (CO3)2-

From what you have, it looks as if you thought there were 3 moles of CO to each mole of Mg, but the ion is (CO3)2-, not (CO)3.

Once you know that, you should get the answer. Instead of your Ksp, the new Ksp you get should be:

Ksp= [Mg2+][CO32-]

From there, they give you the molar solubility, which by molar ratios is the same as the concentration of each ion, and you can solve.

## molar solubility Ksp question?

1) Use the molar solubility 1.55*10^-5 M in pure water to calculate Ksp for Ag2SO3. 2) Use the molar solubility 2.22*10^-8 M in pure water to calculate Ksp for Pd(SCN)2.

(1)

Ksp = [Ag+]^2 [SO3^-2]

[Ag+] = 2x1.55x10^-5

[SO3-2] = 1.55x10^-5

Ksp = 9.61x10^-10 x 1.55x10^-5 = 1.49x10^-14

(2)

Ksp = [Pb+2][SCN^-1]^2

[Pb+2] = 2.22x10^-8

[SCN-] = 4.44x10^-8

Ksp = 4.38x10^-23

## How to calculate Ksp from molar solubility?

A.)If the molar solubility of CaF2 at 35degC is 1.24x10^-2mol/L, what is Ksp at this temperature?? B.) It is found that 1.1x10^-2g of SrF2 dissolves per 100mL of aqueous solution at 25degC. Calculate solubility product constant. Answers: A.)Ksp = 7.63x10^-9 B.) Ksp= 2.7x10^-9 But how?! Help! Thanks!

CaF2 --> Ca 2+ + 2F-

0.0124M CaF2 --> 0.0124M Ca 2+ + 0.0248M F-

Ksp = [Ca2+][F-]^2

Ksp = (0.0124)(0.0248)^2 = 7.63x10^-6

0.011g / 125.6g/mole = 8.76x10^-5moles

8.76x10^-5moles / 0.1L = 8.76x10^-4M

8.76x10^-4M SrF2 --> 8.76x10^-5M Sr 2+ and 1.75x10^-4M F-

Ksp = [Sr2+][F-]^2

Ksp = 8.75x10^-4 x (1.75x10^-4)^2 = 2.68x10^-11

## Use the molar solubility in pure water to calculate Ksp for these three compounds.?

A) Use the molar solubility 1.08 x 10^-5 M in pure water water to calculate Ksp for BaCrO4. B) Use the molar solubility 1.55 x 10^-5 M in pure water water to calculate Ksp for Ag2SO3 C) Use the molar solubility 2.22 x 10^-8 M in pure water water to calculate Ksp for Pd(SCN)2.

A) Ksp = [Ba++][CrO4--]

For every x moles of BaCrO4 that dissolves in a liter of water, the concentration of Ba++ is x Molar, and the concentration of CrO4-- is x Molar. Therefore,

Ksp = (x)(x) = x² = (1.08 x 10^-5 M)² = 1.17 x 10^-10 M².

B) Ksp = [Ag]²[SO3--]

For every x moles of Ag2SO3 that dissolves in a liter of water, the concentration of Ag+ is 2x Molar, and the concentration of SO3-- is x Molar. Therefore,

Ksp = (2x)²(x) = 4x³ = (4)(1.55 x 10^-5 M)³ = 1.49 x 10^-14 M³.

C) Ksp = [Pd++][SCN-]²

In the same manner as question B),

Ksp = (x)(2x)² = 4x³ = (4)(2.22 x 10^-8 M)³ = 4.38 x 10^-23 M³.