Why does the solubility of lithium carbonate decrease with an increase in temperature?

Answer 1

The small lithium ions strongly orient water molecules in solution. At higher temperatures, thermal motion tends to disrupt this orientation, making it more difficult for the ions to enter solution. Thermal motion also tends to disrupt the lithium carbonate crystal, but the effect on organized water is quantitatively larger, enabling entropy to increase by expanding crystals at the expense of the dissolved substance.

Answer 2

The solubility of lithium carbonate decreases with an increase in temperature because it is an endothermic process. As temperature rises, the equilibrium shifts towards the reverse reaction (the solid lithium carbonate forming from the ions in solution) to counteract the increase in temperature, resulting in lower solubility.