What is the #"pH"# for #2.5 xx 10^(-6) "M"# #"HCl"#?

1 Answer
Jun 2, 2016

Answer:

#pH=5.60#

Explanation:

HCl is a strong acid that fully ionizes when dissolved in water according to the following equation:

#HCl + H_2O -> H_3O^+ + Cl^-#

Having 1:1 ratio #=> [H_3O^+] = 2.5xx10^-6\ M#

#pH = -log [H_3O^+]#
#pH = -log(2.5xx10^-6)#
#pH = 5.60#

Note that the contribution of the autoionization of #H_2O# to #[H_3O^+]# is small (in the range of #10^-7 M#) that is why it is neglected. If it was not, it may contribute about one-tenth or so to the #"pH"#.