As you surely know, an increase of solubility with rising temperature is the normal case. When the solubility is codependent with the pH, the trend may reverse, see https://www.researchgate.net/post/Why_such_a_temperature_influence_on_calcite_solubility

Dr Jurgen Weippert thank you for your contribution to the discussion

An increase in pressure and an increase in temperature in this reaction results in greater solubility. An increase in pressure results in more gas particles entering the liquid in order to decrease the partial pressure. Therefore, the solubility would increase. As the temperature of the solution increase, the average kinetic energy of the solute molecules also increases. This causes the molecules to be less able to hold together and hence they dissolve more readily. Hence increase in temperature increases the solubility of solid states. For many solids dissolved in liquid water, the solubility increases with temperature. The increase in kinetic energy that comes with higher temperatures allows the solvent molecules to more effectively break apart the solute molecules that are held together by intermolecular attractions. With an increase in temperature solubility of liquids and solids increases in the same way solubility of gases decreases with an increase in temperature as, when we mix salt or sugar in water. Both will be more easily soluble in hot water as compared to normal or cold water.Conversely, adding heat to the solution provides thermal energy that overcomes the attractive forces between the gas and the solvent molecules, thereby decreasing the solubility of the gas. The phenomenon is similar to that involved in the increase in the vapor pressure of a pure liquid with increasing temperature.Increasing the temperature will therefore increase the solubility of the solute. An example of a solute whose solubility increases with greater temperature is ammonium nitrate, which can be used in first-aid cold packs. Rises in temperature improve the solubility of solids in water, but reduce the solubility of gases in water because temperature increases produce an increase in the number of stimulated atoms or molecules of gases. Changes in pressure have essentially no effect on the solubility of solids and liquids. The trend is thus as follows: increased temperatures mean lesser solubility and decreased temperatures mean higher solubility. Gases increase in solubility as the temperature of the solvent decreases. Gases have the highest energy state between solids, liquids, and gases. When they absorb energy from a warm solvent, they escape the solvent.Because, when temperature is increased, more energy is given to the system, which is used by the gas molecules to overcome the solvent-gas interactions and break free to move into the gaseous state. So, solubility of a gas in liquid decreases with an increase in temperature. Thus, increasing the temperature increases the solubility’s of substances as, sugar and salt are more soluble in water at higher temperatures. The solubility of the gas in a liquid solution decreases with increase in temperature. This is because, with an increase in temperature, the kinetic energy of the gas molecule increases, thus it becomes difficult for liquid molecules to hold them. The solubility of most substances depends strongly on the temperature and, in the case of gases, on the pressure. The solubility of most solid or liquid solutes increases with increasing temperature. The solubility of a solid solute in a liquid solvent increases with increase in temperature. Solubility of the most of the salt rises with increase in temperature. This is because with increase in temperature, kinetic energy of the molecules increases and the solvent molecules break apart the solute molecules that are held together by intermolecular attractions more effectively. On decreasing the temperature, the solubility of a solute in a solution decreases. This means that more solute can be dissolved in the same amount of solvent at higher temperature.

It is known that gaseous solute has a decrease in the solubility with the temperature increase. Thermodynamically we can expect that, since with temperature increase we are giving more kinect energy to the solute, thus it tends to agglomerate with its own molecules than the solvent molecules, escaping from the intermolecular interaction with the solvent;

I think we can extrapolate (with lots and lots of restraints) this case for liquid-liquid and solid-liquid systems. Take for example the nicotine, that is not soluble in water at temperatures between 61 and 210 °C at some concentrations. This can occur due steric conditions inside the molecule that create a more favorable interaction between nicotine-nicotine molecules than nicotin-water; The answer is not always easy. Changes in the crystal structure, molecular dynamics, average kinect energy, all of this will interfere. However, we can approach this by theoretical calculations and experimental methods by the way.

In therms of thermodynamic variables, we can think that Free Gibbs energy is positive for this system for two phases that are not mixing, thus the entropic contribution could be negative. If the mixture enthalpy is /\H < 0, a decrease in temperature will move the free Gibbs energy towards positive values (spontaneous mixture) - This can be checked by /\G = /\H - T/\S.

If /\G < 0, /\H < 0, an increase in the T/\S term will make /\G > 0. This considering that the mixture enthalpy is constant during the temperature range of the study, which sometimes are not, and we may need to considerer the specific caloric capacity of the solute and solvent and use the differential equation.

That is a nice topic of discussion. Hope I could contributed.

Regards,

GG

Dr Gustavo Henrique de Magalhães Gomes thank you for your contribution to the discussion

Gases increase in solubility as the temperature of the solvent decreases. Gases have the highest energy state between solids, liquids, and gases. When they absorb energy from a warm solvent, they escape the solvent. Because, when temperature is increased, more energy is given to the system, which is used by the gas molecules to overcome the solvent-gas interactions and break free to move into the gaseous state so, solubility of a gas in liquid decreases with an increase in temperature. Thus, increasing the temperature increases the solubility of substances as; sugar and salt are more soluble in water at higher temperatures. The solubility of the gas in a liquid solution decreases with increase in temperature. This is because, with an increase in temperature, the kinetic energy of the gas molecule increases, thus it becomes difficult for liquid molecules to hold them. With an increase in temperature solubility of liquids and solids increases in the same way solubility of gases decreases with an increase in temperature as when we mix salt or sugar in water. Both will be more easily soluble in hot water as compared to normal or cold water. On decreasing the temperature, the solubility of a solute in a solution decreases. This means that more solute can be dissolved in the same amount of solvent at higher temperature. The solute's solubility falls because the kinetic energy of the gaseous solute increases as the temperature rises. As a result, its molecules are more likely to escape the solvent molecule's attraction and return to the gas phase. Several substances—HCl, NH3, and SO2—have solubility that decreases as temperature increases. They are all gases at standard pressure. When a solvent with a gas dissolved in it is heated, the kinetic energy of both the solvent and solute increase.The addition of more heat facilitates the dissolving reaction by providing energy to break bonds in the solid. This is the most common situation where an increase in temperature produces an increase in solubility for solids. Cool the mixture and record the temperature, in °C, at which crystals begin to form. The mass of solid added is the mass of this substance required to saturate 10 g of water at the temperature recorded. Multiplying the mass of the substance by 10 gives the solubility in g/100 g water. As the kinetic energy of the gaseous solute increases, its molecules have a greater tendency to escape the attraction of the solvent molecules and return to the gas phase. Therefore, the solubility of a gas decreases as the temperature increases.