Question

A 0.200 M solution of a weak acid, HX, is 9.4 percent ionized. Using this information, calculate Ka for HX.

a) 1.8 × 10⁻³
b) 2.0 × 10⁻³
c) 4.4 × 10⁻²
d) 8.3 × 10⁻²

Answer 1

To calculate Ka for a weak acid, HX, given a 0.200 M solution and 9.4% ionization, you can use the percent ionization and initial concentration of the solution. The resulting Ka value is approximately 1.8 x 10⁻³.

Step-by-step explanation:

To calculate the value of Ka for the weak acid, HX, we can use the percent ionization and the initial concentration of the solution. The percent ionization, 9.4%, can be converted to a decimal by dividing it by 100, giving us 0.094. This represents the fraction of the weak acid that has ionized, or dissociated, into H+ and X-.

Using the initial concentration of the solution, 0.200 M, we can calculate the concentration of the ionized and unionized weak acid. The ionized weak acid (HX) will have a concentration of 0.200 M * 0.094 = 0.0188 M, while the unionized weak acid will have a concentration of 0.200 M - 0.0188 M = 0.1812 M.

Finally, we can use these concentrations to calculate Ka using the equation Ka = [H+][X-] / [HX]. Plugging in the values we calculated, the answer is a) 1.8 x 10⁻³.