Question

Enough of a monoprotic acid is dissolved in water to produce a 0.0147 M solution. The pH of the resulting solution is 2.46. Calculate the pKa for the acid.

Answer 1

First, we need to calculate Ka in order to determine the pKa. 

The formula for Ka = x^2/ initial concentration

initial concentration= 0.0147 M

we need to find x, and we can use the pH to find it because x is the [H+] concentration.

[H+]= 10^-pH----> [H+]= 10^-2.46= 0.00347 

Ka= x^2/ initial---------> (0.00347)^2/ 0.0147= 8.18 x 10^-4

now that we have Ka, we can determine pKa using the following formula--> pKa= -log Ka

pKa= -log (8.18 x 10^-4)= 3.087