Final answer:
The compound PbCl₂ (lead(II) chloride) is insoluble in water, making it the correct answer to the question. Other options like CaCl₂, K2CO₃, and NaNO₃ are all soluble in water.
Step-by-step explanation:
The compound that is insoluble in water from the given options is PbCl₂ (lead chloride).
The solubility of ionic compounds in water depends on the nature of the compound. Lead chloride (PbCl₂) is considered insoluble in water. When PbCl₂ is added to water, it forms a precipitate due to its low solubility.
In contrast, the compounds CaCl₂, K₂CO₃, and NaNO₃ from the other options are soluble in water.
The question asks which one of the following compounds is insoluble in water: PbCl₂, CaCl₂, K2CO₃, or NaNO₃. According to solubility rules, most chlorides are soluble in water, with some exceptions such as silver, mercury, and lead salts. Calcium chloride (CaCl₂), potassium carbonate (K2CO₃), and sodium nitrate (NaNO₃) are all soluble in water. These compounds are part of the groups where all nitrates and most chlorides and carbonates of alkali metals are soluble. However, lead(II) chloride (PbCl₂) is an exception, and it is insoluble in water. Therefore, the correct answer is PbCl₂.