An acid is practically defined as any proton donor in solution (refer to bronsted acids in your chemistry text). the most abundant isotope of h has a single proton for the nucleus, so an acid is capable of readily offering hydrogen ions (h+) when added into a solution. strong acids completely ionize every single h+ available, and weak acids only partially ionize available h+. in most practical applications, acidity / basicity is concerned only with aqueous solutions. when ph is measured or calculated, this is with the understanding that the acid or base is dissolved in water (an aqueous solution). it's theoretically possible to create acids in other solvents, such as liquid ammonia (nh3), but measuring the ph of this solution is an unusual procedure. ph essentially counts the number of h+ ions in a solution-it's a measure of how strong the acidity / basicity of a solution is ph is defined as the negative log (base 10) of the h+ concentration ph = -log(a.) pure water molecules (h20) continuously dissociate into h+ and oh, forming very short lived acid-base conjugate pairs. these pairs only dissociate for a very short time before recombining. this is called the autoionization of water. because this process is constant, pure water has a continuous level of hydrogen ion activity. at room temperature, only about 1 of every 1x10 water molecules are ionized at any moment. this rate of autoionization is constant at a given temperature. mathematically we can define an equilibrium constant that expresses the ratio of h+, oh and h20 at any moment: ( oh) (1.0] or k[h0]-[hor] h o w is known as the ion-product constant for water or k. it's possible to calculate k, using gibbs free energy concepts, but for now know that the equilibrium constant for water k, 1x10 mol/dm. (brackets around a molecular formula denote molarity or concentration in solution) 1) show how pure water has a ph of 7 using the definition of the log and k. one coveat: recall from class that transcendental functions (logs, exponents, trig functions) must not have any units in their argument. how do you manage this in your calculation? 2) a solution has a ph of 6.8. the number of he ions is doubled. what is the resultant ph? 3) a solution has a ph of 4. what is the poh? (let poh be defined as poh = -log(@