The species which are marked with the symbol (aq.) are soluble in water and are dissociated to their free hydrated, provided they are strong electrolytes. Most inorganic ionic solids which are soluble and get dissociated into free ions. These are strong electrolytes. But there are others which are soluble in water but do not dissociate into free ions. Some weak electrolytes like HF, HCN, CH~3~COOH, NH~3~ etc and non-electrolytes C~2~H~5~OH, C~6~H~12~O~6~ etc. though they soluble in water. They are also given the (aq.) symbol. Note that the species marked with the symbol (s), (l) or (g) do not dissociate into ions and hence written as such. (s): solid (insoluble), (l) : liquid, (g) : gas Let us first know how ionic equations are written. For that purpose, let us take an acid-base reaction. You know that an acid reacts with a base to produce a salt