Aqueous solution
An aqueous solution refers to the solution of any hydrophilic substance, often a salt , in water .
That a substance is dissolved in water, in the total formula and in reaction equations by an appended, subscript "( aq (of)" lat. , Aqua ' water ) is displayed, for example, Cl - (aq) for dissolved chloride - ion . On the basis of their solubility, substances are also divided into two groups: hydrophilic ("water-loving"; e.g. sodium chloride ) and hydrophobic ("water-avoiding"; e.g. oils ) substances; In general: Ions and strongly polar substances can be dissolved better in water than weakly polar substances, because water is a dipole , which means that water molecules have a positively and a negatively charged side. For the same reason, only traces of non-polar substances can be dissolved in water; however, even these traces can already be so large that they become noticeable, which can have devastating consequences for oil, for example.
When dissolving, the hydration energy is usually released , although other reactions , especially the dissolution of the ion lattice in the case of salts , can even bring the energy balance into the negative range under certain circumstances.
An important property of many aqueous solutions is that they conduct electricity well , while pure water is a very poor conductor.