Compounds which dissolve in 5% NaOH and 5% NaHCO3 will be classified into Aw group (weak acids) and As group (strong acids), respectively. Thus one can distinguish between weak and strong acids by determining their solubility in both strong (NaOH) and weak (NaHCO3) base. For the purpose of this experiment, carboxylic acids (strong acid pKa 5) are generally indicated when the unknown compound is soluble in both bases, while phenols (weak acid pKa 10) are indicated when a compound is soluble only in NaOH. Compounds dissolve in aqueous base solutions because they form sodium salts that are soluble in aqueous medium. However, the salts of some high molecular weight compounds are not soluble and will precipitate out. The salts of long chain fatty acids such as myristic (C14), palmitic (C16) and stearic (C18) acids are in this category, these salts form soaps.