Final answer:
Among CaSO4, PbCl2, KBr, and KNO3, the compounds CaSO4 and PbCl2 are not soluble in water at room temperature due to their nature and solubility rules.
Step-by-step explanation:
In the context of solubility in water at room temperature, the compounds CaSO4 (calcium sulfate), PbCl2 (lead(II) chloride), KBr (potassium bromide), and KNO3 (potassium nitrate) can be evaluated. According to solubility rules, while compounds of alkali metal ions like K+ are generally soluble, leading to the solubility of KBr and KNO3, there are exceptions for certain other compounds. Specifically, PbCl2 is slightly soluble in water but may be considered insoluble in many practical situations, and CaSO4 has low solubility in water. Therefore, of the compounds listed, CaSO4 and PbCl2 are not soluble in water at room temperature.