How to calculate pKa of #HCl#?

1 Answer
Tanish J. · Media Owl
Nov 28, 2014

The ionisation of HCl can be shown as:

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

#K_a# can be calculated as the ratio of the product of the concentrations of the products to that of the reactant, that is,

#K_a= ([H_3O^+][Cl^-])/([HCl])#

Since #HCl# is a strong acid, the value of #K_a# turns out to be very large, that is,

#K_a=10^7/1=10^7# (approx.)

The value of #pK_a# is given by

#pK_a=-logK_a#
#pK_a=-(log10^7)#
#pK_a=-(7)=-7#

You can learn more about finding the values of #K_a# and #pK_a# [here.](https://www.khanacademy.org/science/organic-chemistry/organic-structures/acid-base-review/v/ka-and-pka-derivation)

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