questions about chemistry?

H4Cl??? There is no H4Cl. There is HCl, hydrogen chloride gas. And when it is dissolved in water it is called hydrochloric acid. Like all gases, as the temperature increases, the solubility decreases. A saturated solution is an equilibrium between the gas and the dissolved gas. As temperature increases, the equilibrium is shifted toward the gas phase. It's a matter of entropy. HCl as a gas is higher in entropy than as a solute in solution.

The same is true for a solid dissolved in water. As the temperature increases, more of the solid KNO3 in equilibrium with dissolved KNO3 will dissociate to form ions, thus increasing the solubility.