When dissolved in water, what do acids produce?

1 Answer
anor277
May 2, 2017

Dissolution of a gas in water causes an increase in the concentration of the characteristic cation of the solvent, i.e. #H_3O^+#, the #"hydronium ion"#.

Explanation:

We (well) know that water undergoes autoprotolysis......which we represent as:

#2H_2O(l) rightleftharpoonsH_3O^+ + HO^-#

And such protolysis may be quantitatively measured...

#K_w=[H_3O^+][HO^-]=10^-14#

Taking #log_10# of both sides we get...........on rearrangement.

#-log_10(10^-14)=-log_10[H_3O^+]-log_10[HO^-]#

But #-log_10(10^-14)=-(-14)=14# by definition, and also #pH=-log_10[H_3O^+]# and #pOH=-log_10[HO^-]#, i.e. #pH+pOH=14#.

And so the moral, dissolution of an acid in water causes AN INCREASE in the concentration of the characteristic cation, #H_3O^+#, and a DECREASE in #pH#.

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