Final answer:
The substances CaCO₃ and BaSO₄ are only slightly soluble in water due to their low solubility products. The solubility of CaCO₃ can increase with carbon dioxide, while BaSO₄ is not soluble in water, leading to precipitation.
Step-by-step explanation:
The substances CaCO₃ (calcium carbonate) and BaSO₄ (barium sulfate) are only slightly soluble in water. This limited solubility is because both calcium carbonate and barium sulfate have low solubility products in water, which means they do not dissociate significantly into their ions in water. Notably, while certain compounds like NaCl and (NH₄)₃PO₄ are readily soluble in water, there are exceptions like CaCO₃ and BaSO₄ due to their insoluble nature.
It is important to note that the solubility of substances like CaCO₃ can be increased in the presence of carbon dioxide due to the formation of carbonic acid, which helps the dissolution process. For BaSO₄, it precipitates according to the net ionic equation Ba²⁺ (aq) + SO⁴²⁺ (aq) → BaSO₄(s) as it is not soluble in water.