Solutions And Solubility Homework Pass

Temperature changes affect the solubility of solids, liquids and gases differently. However, those effects are finitely determined only for solids and gases.

Solids

The effects of temperature on the solubility of solids differ depending on whether the reaction is endothermic or exothermic. Using Le Chatelier's principle, the effects of temperature in both scenarios can be determined.

  1. First, consider an endothermic reaction (\(\Delta{H_{solvation}}>0\)): Increasing the temperature results in a stress on the reactants side from the additional heat. Le Châtelier's principle predicts that the system shifts toward the product side in order to alleviate this stress. By shifting towards the product side, more of the solid is dissociated when equilibrium is again established, resulting in increased solubility.
  2. Second, consider an exothermic reaction ((\(\Delta{H_{solvation}}<0\)): Increasing the temperature results in a stress on the products side from the additional heat. Le Châtelier's principle predicts that the system shifts toward the reactant side in order to alleviate this stress. By shifting towards the reactant's side, less of the solid is dissociated when equilibrium is again established, resulting in decreased solubility.

Gases

In understanding the effects of temperature on the solubility of gases, it is first important to remember that temperature is a measure of the average kinetic energy. As temperature increases, kinetic energy increases. The greater kinetic energy results in greater molecular motion of the gas particles. As a result, the gas particles dissolved in the liquid are more likely to escape to the gas phase and the existing gas particles are less likely to be dissolved. The converse is true as well. The trend is thus as follows: increased temperatures mean lesser solubility and decreased temperatures mean higher solubility.

Le Chatelier's principle allows better conceptualization of these trends. First, note that the process of dissolving gas in liquid is usually exothermic. As such, increasing temperatures result in stress on the product side (because heat is on the product side). In turn, Le Chatelier's principle predicts that the system shifts towards the reactant side in order to alleviate this new stress. Consequently, the equilibrium concentration of the gas particles in gaseous phase increases, resulting in lowered solubility.

Conversely, decreasing temperatures result in stress on the reactant side (because heat is on the product side). In turn, Le Châtelier's principle predicts that the system shifts toward the product side in order to compensate for this new stress. Consequently, the equilibrium concentration of the gas particles in gaseous phase would decrease, resulting in greater solubility.

  • Upon your observation; Solutes follow Like dissolve like principle to decide the extent to which they will get dissolved into solvent. It means more ionic solute will dissolve more in a polar solvent than a non-polar solvent and vice-versa.
  • KOH has a greater ionic character than NaOH and hence needs a more polar solvent to get dissolved as compared to the equivalent amount of NaOH needs to be. Since alcohols are very less polar, they may break bindings of NaOH effectively but are not able to break those of KOH to that extent. As a result KOH is less soluble in alcohols. This is also evident from the fact that KOH is more soluble in water as compared to NaOH because water is a polar solvent and hence it finds KOH more perfect match than NaOH.

  • As we all know solubility is a temperature-dependent property and does not possesses same slopes for all solutes. Hence you may get a lower solubility for KOH at some temperature.

  • By the word "Alcohols" we do not have a specific solvent and hence different solute-solvent pairs are possible and do not know exactly which alcohol you're discussing as some halogenated alcohol have greater affinity for NaOH.

  • Because of smaller size of sodium ion, hydration ease is another factor you should not ignore while concerning this.

  • Finally there are several other factors which leads to the greater solubility which include charge density, bond stability, percent ionic character etc. studying which may or may not give results contrary to your question.

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