Final answer:
The molar solubility of BaCrO₄ in pure water is approximately 4.59 × 10⁻⁵ M. The molar solubility of BaCrO₄ in 8.0 × 10⁻³ M Na₂CrO₄ cannot be determined without additional information.
Step-by-step explanation:
To find the molar solubility of BaCrO₄, we need to compare the value of Ksp with the concentration of BaCrO₄ in the solution. Let's solve each part of the question:
(a) To find the molar solubility of BaCrO₄ in pure water, we need to calculate the concentration of BaCrO₄ when Ksp is equal to the solubility product. Since the Ksp value is given as 2.1 × 10⁻¹⁰, the molar solubility of BaCrO₄ in pure water is approximately 4.59 × 10⁻⁵ M.
(b) To find the molar solubility of BaCrO₄ in 8.0 × 10⁻³ M Na₂CrO₄, we need to consider the common ion effect. The Na₂CrO₄ will provide additional CrO₄²⁻ ions, which will affect the solubility. Using the common ion effect equation, we can calculate the molar solubility of BaCrO₄. However, since the necessary information is not provided, we cannot determine the molar solubility in this mixture.