A 0.60 M solution of a weak acid, HA, has a pH of 3.72. What is the percentage ionization of the acid? What is the value of Ka for the acid?

pH = -log(H^+)

pH = 3.72; (H^+) = approx 2E-4 but that's an approximation. You should do this more accurately as well as all of the calculations that follow.

%ion = [(H^+)/Msample]*100

...........HA ==> H^+ + A^-
I.........0.6.....0......0
C...........-x....x......x
E........0.6-x....x......x

You know x is approx 2E-4, Substitute that for x into the Ka expression for HA and solve for Ka.

To calculate the percentage ionization of the acid, we need to determine the concentration of the ionized form of the acid (A-) and the concentration of the unionized form (HA). If we assume that x represents the amount of HA that has ionized, we can write the following equilibrium equation:

HA ⇌ H+ + A-

Since we know the initial concentration of the acid is 0.60 M, the concentration of the ionized form (A-) is also x M, and the concentration of the unionized form (HA) is (0.60 - x) M.

Now, we need to calculate the concentration of H+ ions. Since pH is defined as the negative logarithm (base 10) of the concentration of H+ ions, we can calculate the concentration of H+ ions using the formula:

[H+] = 10^(-pH)

Substituting the given pH value, we find:

[H+] = 10^(-3.72)

Now, we can assume that most of the acid is unionized, meaning the value of x is small compared to 0.60. Therefore, we can ignore x when calculating the concentration of H+ ions and consider (0.60 - x) as approximately equal to 0.60.

Using the equation for the ionization constant (Ka) of the weak acid, which is given by:

Ka = [H+][A-] / [HA]

we can substitute the values we have:

Ka = ([H+])(x) / (0.60)

Now we can solve for x by rearranging the equation:

x = (Ka * 0.60) / [H+]

Using the concentration of H+ ions we calculated earlier, we can now calculate the value of x, which represents the concentration of the ionized form of the acid (A-).

Next, we can calculate the percentage ionization by using the formula:

Percentage ionization = (x / initial concentration of HA) * 100

Substituting the values we have, we can finally calculate the percentage ionization.

To calculate the value of Ka for the acid, we can use the equation we derived earlier:

Ka = ([H+])(x) / (0.60)

Now that we know the concentration of H+ ions and the concentration of A-, we can calculate Ka.

Remember, in solving these calculations, always double-check the assumptions and verify whether they are valid based on the given values and conditions.