Answer to Question #170829 in General Chemistry for Mayuka

Question

Allotropes are substances with the same chemical formula but have different forms (e.g. crystal structure). An example of an allotropic pair is aragonite and calcite. The chemical formula of aragonite and calcite is CaCO3. Due to the difference in their crystal structure, their Ksp values are different. The Ksp of aragonite is 6.0  10-9 while that of calcite is 3.36  10-9.

A. Write the chemical equation for the dissociation of CaCO3 in water.

B. Write the Ksp expression for CaCO3.

C. Which between aragonite and calcite is more soluble? Why? 

Answer 1

A. CaCO3 = Ca^2+ + CO3^2-

B. CaCO 34.5 × 10 -9.

C. Scientists are particularly interested in aragonite, which is produced by many tropical corals, cold-water corals, pteropods and some molluscs. It is more soluble than calcite. Organisms grow shells and skeletons more easily when carbonate ions in water are abundant – it is supersaturated.