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Bromine in excess is dropped to a 0.01 M...

Bromine in excess is dropped to a 0.01 M `SO_(2)`. All of `SO_(2)` is oxidized to `H_(2)SO_(4)` and the excess `Br_(2)` is removed by flushing with gaseous `N_(2)`. Determine the pH of the resulting solution assuming `K_(a1)` of `H_(2)SO_(4)` vary large & `K_(a2) = 10^(-2)`. Take the value of `log (3.24) = 0.51`.

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To determine the pH of the resulting solution after the oxidation of SO₂ to H₂SO₄ by excess bromine, we can follow these steps: ### Step-by-Step Solution: 1. **Identify the Reactions**: The oxidation of sulfur dioxide (SO₂) to sulfuric acid (H₂SO₄) can be represented as: \[ \text{SO}_2 + \text{Br}_2 \rightarrow \text{H}_2\text{SO}_4 + \text{HBr} \] Given that the concentration of SO₂ is 0.01 M, after the reaction, we will have: - H₂SO₄ produced: 0.01 M - HBr produced: 0.02 M (since 2 moles of HBr are produced for every mole of SO₂ oxidized). 2. **Concentration of H⁺ Ions from HBr**: HBr is a strong acid and will completely dissociate in solution: \[ \text{HBr} \rightarrow \text{H}^+ + \text{Br}^- \] Thus, the concentration of H⁺ ions from HBr will be: \[ [\text{H}^+] = 0.02 \text{ M} \] 3. **Concentration of H⁺ Ions from H₂SO₄**: H₂SO₄ is a strong acid for its first dissociation: \[ \text{H}_2\text{SO}_4 \rightarrow \text{H}^+ + \text{HSO}_4^- \] The first dissociation is complete, contributing 0.01 M of H⁺ ions. The second dissociation is: \[ \text{HSO}_4^- \rightleftharpoons \text{H}^+ + \text{SO}_4^{2-} \] Given that \( K_{a2} = 10^{-2} \), we can set up the equilibrium expression: \[ K_{a2} = \frac{[\text{H}^+][\text{SO}_4^{2-}]}{[\text{HSO}_4^-]} \] 4. **Setting Up the Equilibrium**: Let \( x \) be the amount of H⁺ produced from the dissociation of HSO₄⁻. The concentrations at equilibrium will be: - \([\text{H}^+] = 0.02 + x\) - \([\text{HSO}_4^-] = 0.01 - x\) - \([\text{SO}_4^{2-}] = x\) Substituting into the \( K_{a2} \) expression: \[ 10^{-2} = \frac{(0.02 + x)(x)}{(0.01 - x)} \] 5. **Approximating x**: Assuming \( x \) is small compared to 0.01, we can simplify: \[ 10^{-2} \approx \frac{(0.02)(x)}{0.01} \] Solving for \( x \): \[ 10^{-2} \cdot 0.01 = 0.02x \implies x = \frac{10^{-4}}{0.02} = 0.005 \] 6. **Total H⁺ Concentration**: Now, we can find the total concentration of H⁺ ions: \[ [\text{H}^+] = 0.02 + 0.005 = 0.025 \text{ M} \] 7. **Calculating pH**: The pH is calculated using the formula: \[ \text{pH} = -\log[\text{H}^+] \] Substituting the value: \[ \text{pH} = -\log(0.025) = -\log(3.24 \times 10^{-2}) = 2 - \log(3.24) \] Given that \(\log(3.24) = 0.51\), \[ \text{pH} = 2 - 0.51 = 1.49 \] ### Final Answer: The pH of the resulting solution is **1.49**.
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