Answer:
HNO₂ ⇄ H⁺ + NO₂⁻
Ka = 4.0 × 10⁻⁴
Explanation:
Step 1: Given data
- Concentration of nitrous acid (Ca): 0.010 M
Step 2: Write the acid dissociation reaction
Nitrous acid is a weak acid that dissociates according to the following expression.
HNO₂ ⇄ H⁺ + NO₂⁻
Step 3: Calculate the concentration of H⁺
We will use the definition of pH.
pH = -log [H⁺]
[H⁺] = antilog - pH = antilog -2.70 = 2.00 × 10⁻³ M
Step 4: Calculate the acid dissociation constant (Ka)
For a weak acid, we can calculate Ka using the following expression.
Ka = [H⁺]²/Ca
Ka = (2.00 × 10⁻³)²/0.010
Ka = 4.0 × 10⁻⁴
