Question

The solubility product constant of calcium sulfate, CaSO4, is 7.10×10−5. Its molar mass is 136.1 g/mol. How many grams of calcium sulfate can dissolve in 41.5 L of pure water

Answer 1

the mass of calcium sulfate that can be dissolved = 47.64 grams

Step-by-step explanation:

Ksp of CaSO₄ = 7.10X10⁻⁵

The expression for Ksp will be:

Ksp = [Ca⁺²][SO₄⁻²]

Let solubility of CaSO₄ = s

Therefore

[Ca⁺²] = [SO₄⁻²]=s

Ksp = s² = 7.10X10⁻⁵

s = 8.43 X10⁻³ mol/L

this is the solubility thus this is the moles of calcium sulfate that can be dissolved per litre of pure water.

So the moles that can be dissolved in 41.5 L of water

= 8.43 X10⁻³X41.5 = 0.35 moles

the mass of calcium sulfate that can be dissolved = moles X molar mass

the mass of calcium sulfate that can be dissolved = 0.35X136.1 = 47.64 grams