What is the pH of a 3.40 M solution of HNO₂ (Ka = 4.5 x 10-4)? Your Answer: Answer

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**Question:**

What is the pH of a 3.40 M solution of HNO₂ (Kₐ = 4.5 x 10⁻⁴)?

**Response Section:**

- Your Answer: [Text Box]

This question requires you to calculate the pH of a nitrous acid solution using the given concentration and acid dissociation constant (Kₐ). 

**Instructions for Solving:**

1. Write the dissociation equation for nitrous acid (HNO₂):
   \[
   \text{HNO}_2 \rightleftharpoons \text{H}^+ + \text{NO}_2^-
   \]

2. Set up the expression for the acid dissociation constant (Kₐ):
   \[
   Kₐ = \frac{[\text{H}^+][\text{NO}_2^-]}{[\text{HNO}_2]}
   \]
   where:
   - [H⁺] = concentration of hydrogen ions
   - [NO₂⁻] = concentration of nitrite ions
   - [HNO₂] = initial concentration minus the change in concentration x due to dissociation

3. Use the given concentration of HNO₂ to determine changes in concentration:
   - Initial: [HNO₂] = 3.40 M, [H⁺] = 0, [NO₂⁻] = 0
   - Change: [HNO₂] = 3.40 - x, [H⁺] = x, [NO₂⁻] = x

4. Assume x is much less than the initial concentration (3.40 M), simplifying the Kₐ equation:
   \[
   4.5 \times 10^{-4} = \frac{x^2}{3.40}
   \]

5. Solve for x to find [H⁺]:
   - x = [H⁺] = √(3.40 * 4.5 x 10⁻⁴)

6. Calculate the pH:
   \[
   \text{pH} = -\log[\text{H}^+]
   \]

Fill in your answer in the text box provided.
Transcribed Image Text:**Question:** What is the pH of a 3.40 M solution of HNO₂ (Kₐ = 4.5 x 10⁻⁴)? **Response Section:** - Your Answer: [Text Box] This question requires you to calculate the pH of a nitrous acid solution using the given concentration and acid dissociation constant (Kₐ). **Instructions for Solving:** 1. Write the dissociation equation for nitrous acid (HNO₂): \[ \text{HNO}_2 \rightleftharpoons \text{H}^+ + \text{NO}_2^- \] 2. Set up the expression for the acid dissociation constant (Kₐ): \[ Kₐ = \frac{[\text{H}^+][\text{NO}_2^-]}{[\text{HNO}_2]} \] where: - [H⁺] = concentration of hydrogen ions - [NO₂⁻] = concentration of nitrite ions - [HNO₂] = initial concentration minus the change in concentration x due to dissociation 3. Use the given concentration of HNO₂ to determine changes in concentration: - Initial: [HNO₂] = 3.40 M, [H⁺] = 0, [NO₂⁻] = 0 - Change: [HNO₂] = 3.40 - x, [H⁺] = x, [NO₂⁻] = x 4. Assume x is much less than the initial concentration (3.40 M), simplifying the Kₐ equation: \[ 4.5 \times 10^{-4} = \frac{x^2}{3.40} \] 5. Solve for x to find [H⁺]: - x = [H⁺] = √(3.40 * 4.5 x 10⁻⁴) 6. Calculate the pH: \[ \text{pH} = -\log[\text{H}^+] \] Fill in your answer in the text box provided.
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