And of course values of #pH<7# indicate an acidic solution. #pH#, literally #"pouvoir hydrogen"#, measures the concentration of #H_3O^+#, conceived to be the acidic entity in aqueous solution. Extensive measurement has confirmed the following equilibrium in water under standard conditions:
#2H_2O(aq) rightleftharpoons H_3O^+ + HO^-#
And this reaction can be quantified by taking the ion product:
#[H_3O^+][HO^-]=10^(-14)#
If we take #-log_10# of both sides we get,
#-log_10[H_3O^+]-log_10[HO^-]=14#
But under our standard defintion of #pH# and #pOH#,
#pH+pOH=14#
And thus values of #pH>7# indicate a preponderance of hydroxide ions, and #pH<7# indicates a preponderance of hydronium ions.
What is #pH# at neutrality? Why?
