Calcium carbonate is used to form exoskeletons. It has a solubility-product constant of 5.0 $\times$ 10 ^-9. What is the molar concentration of calcium ions in a saturated solution of calcium carbonate? A)2.5 $\times$ 10^-9 M B)7.1 $\times$ 10^-5 M C)3.5 $\times$ 10 ^-5 M D)5.0 $\times$ 10^-9 M E)4.7 $\times$ 10 ^-7 M

Question

Quizplus · Accepted Answer

The solubility-product constant (Ksp) for calcium carbonate (CaCO3) is given as 5.0 x 10^-9. The dissolution of calcium carbonate can be represented as CaCO3(s) ⇌ Ca^2+(aq) + CO3^2-(aq). Since the stoichiometry of the dissolution is 1:1 for calcium ions to carbonate ions, the concentration of calcium ions ([Ca^2+]) will be equal to the concentration of carbonate ions ([CO3^2-]) in a saturated solution. Therefore, if we let [Ca^2+] = [CO3^2-] = x, then Ksp = [Ca^2+][CO3^2-] = x^2. Solving for x gives x = sqrt(Ksp) = sqrt(5.0 x 10^-9) = 7.1 x 10^-5 M, which corresponds to the molar concentration of calcium ions in the solution.

Calcium Carbonate Is Used to Form Exoskeletons ×\times× 10 -9 ×\times× 10-9 M B)7

Calcium Carbonate Is Used to Form Exoskeletons $\times$ 10 ^-9 $\times$ 10^-9 M
B)7