Which of the following compounds is the least soluble in water?
Answer Details
The solubility of a compound in water is determined by its ability to dissociate into ions in the water. Compounds that dissociate completely into ions are more soluble in water than those that do not dissociate as much. Looking at the given compounds, CaCl2 dissociates into three ions (Ca2+ and two Cl-) in water and NaCl dissociates into two ions (Na+ and Cl-). CaSO4 dissociates into two ions (Ca2+ and SO42-) but it is less soluble than CaCl2 because the SO42- ion is larger and more polar than the Cl- ion, so it has a stronger attraction to the Ca2+ ion, making it more difficult to dissociate. Na2SO4 dissociates into three ions (two Na+ and SO42-) but it is also less soluble than NaCl because of the larger, more polar SO42- ion. Therefore, CaSO4 is the least soluble compound in water because it has a weaker ability to dissociate into ions in water compared to the other given compounds.