Match each term with its definition. the position of an equilibrium always shifts in such a direction as to relieve a stress applied to the system. a molecule that donates a proton when it encounters a proton acceptor. occurs when a reaction involving an acid and its conjugate base is combined with a second reaction involving a base and its conjugate acid. it ionizes completely when dissolved in water. the shift in the position of equilibrium caused by the addition of a participating ion. it only partially ionizes when dissolved in water. it is capable of acting as either an acid or a base depending upon the solute. the act of self-ionization of a solvent to produce both a conjugate acid and a conjugate base. a chemical species that bears both positive and negative charges.