Among the following Ka values, which represents the strongest acid?

Question

A. Ka = 1.2 x 10-3
B. Ka = 3.4 x 10-5
C. Ka = 8.7 x 10-8
D. Ka = 5.8 x 10-10

would the answer be A? please explain, don't just give me the answer.

Answer 1

Yes, A is the correct answer.
In the acid, HA, it ionizes as
HA ==> H^+ + A^-
Ka = (H^+)(A^-)/(HA)
The acidity of a solution depends upon the (H^+) so the higher that is the stronger the acid. Look at Ka values. If Ka is large then the numerator (the H^+) is larger. For the choices given,
A is stronger than B which is stronger than C which is stronger than D.