Calculate the percent ionization of nitrous acid in a solution that is 0.222 M in nitrous acid (HNO₂)and 0.278 M in potassium nitrite (KNO₂).The acid dissociation constant of nitrous acid is 4.50 × 10^-4. A)55.6 B)0.162 C)15.5 D)2.78 × 10^-³ E)3.448

Question

Quizplus · Accepted Answer

The percent ionization of nitrous acid can be calculated using the acid dissociation constant and the initial concentrations of nitrous acid and potassium nitrite.

First, we need to calculate the concentration of HNO2 that ionizes:

HNO2 ⇌ H+ + NO2-

Let x be the concentration of H+ and NO2-. At equilibrium, the concentration of undissociated HNO2 is (0.222 - x), and the concentration of NO2- is 0.278 + x.

The equilibrium constant expression for this reaction is:

Ka = [H+] [NO2-] / [HNO2]

Substituting in the equilibrium concentrations:

4.50 × 10^-4 = x * (0.278 + x) / (0.222 - x)

This is a quadratic equation that can be solved for x using the quadratic formula. The resulting value of x is 0.036 M.

The percent ionization is then:

% ionization = (x / 0.222) * 100

% ionization = (0.036 / 0.222) * 100

% ionization = 0.162 or 16.2%

Calculate the Percent Ionization of Nitrous Acid in a Solution