Answer to Question #111143 in General Chemistry for mya 11

Question

A generic salt, AB2 , has a molar mass of 151 g/mol and a solubility of 3.80 g/L at 25 °C.

AB2(s)↽−−⇀A2+(aq)+2B−(aq)

What is the

Answer 1

Correct task : A generic salt AB₂, has a molar mass of 151 g/mol and a solubility of 3.80 g/L at 25^oC. What is the K_sp of this salt at 25^oC.

Solution:

When the salt dissolves, it dissociates as follows:

AB₂ --> A²⁺ + 2B⁻

--S--------S-------2S--

The molar solubility (S) is the number of moles that can dissolve in 1 L of solution.

Molar solubility of salt is (3.80 g/L) / (151 g/mol) = 0.0252 mol/L.

According to the dissociation equation:

Solubility of A²⁺ is 0.0252 mol/L and solubility of B⁻ is 2×0.0252 mol= 0.0504 mol/L.

[A²⁺] = 0.0252 mol/L.

[B⁻] = 0.0504 mol/L.

K_sp is the solubility product constant and calculated as follows:

K_sp(AB₂) = [A²⁺] × [B⁻]²

K_sp(AB₂) = [0.0252] × [0.0504]²

K_sp(AB₂) = 6.40×10^-5.

K_sp of this salt is 6.40×10^-5.

Answer: 6.40×10^-5 is the K_sp of this salt at 25^oC.