Q1: Sodium __________ has inverted solubility curve i.e. its solubility increases with the lowering of temperature.

ANS:A - carbonate (monohydrate)

Sodium carbonate monohydrate (𝑁𝑎2𝐶𝑂3⋅𝐻2𝑂Na2​CO3​⋅H2​O) is a hydrated form of sodium carbonate. In this compound, one molecule of water (𝐻2𝑂H2​O) is associated with each formula unit of sodium carbonate (𝑁𝑎2𝐶𝑂3Na2​CO3​). When this compound dissolves in water, the water molecules interact with the crystal lattice of sodium carbonate, surrounding each sodium carbonate molecule with water molecules. This hydration process affects the solubility of sodium carbonate monohydrate. The solubility of sodium carbonate monohydrate exhibits an unusual behavior, known as an inverted solubility curve. In an inverted solubility curve, the solubility of the compound increases as the temperature decreases. This is contrary to the typical behavior of most salts, where solubility generally increases with temperature. The reason for the inverted solubility curve of sodium carbonate monohydrate lies in the hydration process. At higher temperatures, the energy provided to the system disrupts the hydration bonds between