Question

Given the choice of adding ions of Mg ²⁺ (aq), Ca ²⁺ (aq), Sr ²⁺ (aq) or Ba ²⁺ (aq) to a solution of carbonate ions, CO₃ ²⁻, which choice would precipitate an insoluble carbonate compound first? Use the following Ksp data:

MgCO₃ Kₛₚ = 6.82 x 10⁻⁶
CaCO₃ Kₛₚ = 4.96 x 10⁻⁹
SrCO₃ Kₛₚ = 9.30x 10⁻¹⁰
BaCO₃ Kₛₚ = 5.00 x 10⁻⁹

A) Mg ²⁺
B) Ca ²⁺
C) Sr ²⁺
D) Ba ²⁺
E) none of these will give a precipitate

Answer 1

The correct answer is option A. Mg²⁺(aq) will precipitate an insoluble carbonate compound first.

Step-by-step explanation:

When comparing the Ksp values for the different carbonate compounds, we can determine which one will precipitate first. Among the given choices, the carbonate compound with the lowest Ksp value will precipitate first. The Ksp values for the different carbonates are as follows:

• MgCO3: 6.82 x 10-6
• CaCO3: 4.96 x 10-9
• SrCO3: 9.30 x 10-10
• BaCO3: 5.00 x 10-9

Based on these values, we can see that MgCO3 has the smallest Ksp value and will therefore precipitate first. So, the choice that will precipitate an insoluble carbonate compound first is A) Mg2+.