What is the percent ionization of a 1.38 mol/L weak acid if its Ka = 2.7 x 10^-6?
Thanks again!
Write the ionization equation. I would call the weak acid HA.
Write the Ka expression.
Set up an ICE chart if that will help.
Let y = (H^+), then (A^-) will be y and the unionized HA will be 1.38 - y.
Substitute these variables into the Ka expression and solve for y = (H^+).
Then percent ionization =
[(H^+)/(HA)]*100 = ??
Post your work if you need further help.
To find the percent ionization of a weak acid, you need to know its Ka value, which is a measure of its acidity. The Ka value represents the extent of ionization of the weak acid in water.
The ionization of a weak acid can be represented by the following equation:
Weak Acid (HA) + H2O ↔ H3O+ + A-
The Ka expression for this reaction is:
Ka = [H3O+][A-] / [HA]
Given the Ka value of 2.7 x 10^-6, we know that at equilibrium, the concentration of [H3O+] and [A-] will be equal and can be represented as x. The equilibrium concentration of [HA] can be represented as (1.38 - x) because some of the weak acid will ionize.
Substituting the values into the Ka expression, we have:
2.7 x 10^-6 = x^2 / (1.38 - x)
To solve for x, we rearrange the equation:
2.7 x 10^-6 = x^2 / (1.38 - x)
Multiply both sides by (1.38 - x):
2.7 x 10^-6 (1.38 - x) = x^2
Expand:
3.726 x 10^-6 - 2.7 x 10^-6 x = x^2
Rearrange the equation to form a quadratic equation:
x^2 + 2.7 x 10^-6 x - 3.726 x 10^-6 = 0
To solve this equation, you can use the quadratic formula:
x = (-b ± √(b^2 - 4ac)) / (2a)
For this equation, a = 1, b = 2.7 x 10^-6, and c = -3.726 x 10^-6.
Substituting these values into the quadratic formula:
x = (-(2.7 x 10^-6) ± √((2.7 x 10^-6)^2 - 4(1)(-3.726 x 10^-6))) / (2(1))
Simplify and solve for x using a calculator. You will get two values for x.
Once you have the value of x, you can calculate the percent ionization:
Percent Ionization = (x / initial concentration of HA) * 100
Substitute the value of x and the initial concentration of HA (1.38 mol/L) into the formula to get the percent ionization of the weak acid.