Solved: Drinking water is often disinfected with Cl2,

Chapter 18, Problem 119P

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Drinking water is often disinfected with chlorine gas, which hydrolyzes to form hypochlorous acid \((\mathrm{HClO})\), a weak acid but powerful disinfectant:

\(\mathrm{Cl}_{2}(a q)+2 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow \mathrm{HClO}(a q)+\mathrm{H}_{3} \mathrm{O}^{+}(a q)+\mathrm{Cl}^{-}(a q)\)

The fraction of $\mathrm{HClO}$ in solution is defined as

\(\frac{[\mathrm{HClO}]}{[\mathrm{HClO}]+\left[\mathrm{ClO}^{-}\right]}\)

(a) What is the fraction of \(\mathrm{HClO}\) at \(\mathrm{pH} 7.00\left(K_{\mathrm{a}}\right.\) of \(\mathrm{HClO}=\) \(2.9 \times 10^{-8}\) )? (b) What is the fraction at \(\mathrm{pH} 10.00\) ?

Equation Transcription:

Text Transcription:

Cl2(aq) + 2H2O(l) → HClO(aq) + H3O+(aq) + Cl⎺(aq)

HClOHClO + ClO ⎺

pH 7.00 (Ka of HClO = 2.9x10-8)