To calculate the percent ionization of nitrous acid (HNO2) in the given solution, we can use the acid dissociation constant (Ka) and the initial concentration of the acid.
The equation for the ionization of nitrous acid is:
HNO2 ⇌ H+ + NO2-
The acid dissociation constant (Ka) is given as 4.50 × 10^-4.
We are given the initial concentration of nitrous acid (HNO2) as 0.311 M.
Step 1: Write the expression for the percent ionization:
Percent ionization = (concentration of H+ ions / initial concentration of HNO2) × 100
Step 2: Calculate the concentration of H+ ions at equilibrium:
We can assume that initially, x amount of the nitrous acid ionizes, resulting in x amount of H+ ions and x amount of NO2- ions. Therefore, the concentration of H+ ions at equilibrium is also x.
Step 3: Use the acid dissociation constant (Ka) to write an expression for the equilibrium concentration of H+ ions and NO2- ions:
Ka = [H+][NO2-] / [HNO2]
Since the concentration of H+ ions and NO2- ions is x and the initial concentration of HNO2 is 0.311 M, we can substitute these values in the equation:
4.50 × 10^-4 = x^2 / 0.311
Solving for x, we find:
x ≈ 0.00539 M
Step 4: Calculate the percent ionization:
Percent ionization = (concentration of H+ ions / initial concentration of HNO2) × 100
= (0.00539 / 0.311) × 100
≈ 1.73%
Therefore, the percent ionization of nitrous acid (HNO2) in the given solution is approximately 1.73%.