In the graphic, the first reaction shows citric acid producing hydrogen ions, therefore it is an acid. Bronsted-Lowery Definition (1923) - The definition of acids and bases involving hydrogen and hydroxide ions, respectively is much too limiting. A broader definition was proposed by Bronsted and Lowry in 1923. The main effect of the definition is to increase the number of substances that act as bases.
Although the solubility of a solid generally increases with increasing temperature, there is no simple relationship between the structure of a substance and the temperature dependence of its solubility. Many compounds (such as glucose and CH3CO2Na) exhibit a dramatic increase in solubility with increasing temperature.
Solubility is a chemical property referring to the ability for a given substance, the solute, to dissolve in a solvent. It is measured in terms of the maximum amount of solute dissolved in a solvent at equilibrium. The resulting solution is called a saturated solution. Certain substances are soluble in all proportions with a given solvent, such as ethanol in water. This property is known as miscibility. Under various conditions, the equilibrium solubility can be exceeded to give a so-called supersaturated solution, which is metastable.