Acid strength is measured by the extent of the overall reaction of the acid with water.
K a is known as the acid dissociation constant and the acid ionization constant. We set up a table like we did in Chapter 14. The degree of dissociation is the fraction of molecules that react with water to give ions. As the original concentration decreases the percent dissociation increases. K a for acetic acid is 1.7 X 10 -5 .