Question

A student prepared a saturated solution of CaCrO4 and found that when 156 mL of the solution was evaporated, 0.649 g of CaCrO4 was left behind. What is the value of Ksp for this salt?

Answer 1

To calculate the Ksp for CaCrO4, the mass of the solute in the given solution volume must be converted to moles to find the molar concentration. The concentrations of Ca2+ and CrO42- are equivalent in a saturated solution. Ksp is found by multiplying these concentrations.

Step-by-step explanation:

To find the value of the solubility product constant (Ksp) for calcium chromate (CaCrO4), we need to ascertain the concentration of the calcium ions (Ca2+) and the chromate ions (CrO42-) present in the solution at saturation. When 156 mL of the saturated solution was evaporated, 0.649 g of CaCrO4 was left, indicating that this mass of solute was present in the 156 mL solution.

Using the molar mass of CaCrO4, we can convert the mass to moles. Dividing by the volume of the solution gives us the molar concentration. Saturation implies that for every mole of CaCrO4 that dissolves, one mole of Ca2+ and one mole of CrO42- are produced. Thus, their concentrations in the solution will be the same. The Ksp expression for CaCrO4 will be Ksp = [Ca2+][CrO42-], where [Ca2+] and [CrO42-] are the concentrations of the respective ions in moles per liter (M).

Substituting these values into the Ksp expression and finding the product will give the Ksp for CaCrO4.