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Question
How will the pH of brine (aq. \[\ce{NaCl}\] solution) be affected when it is electrolysed?
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Solution
\[\ce{NaCl (aq) -> Na^{+} (aq) + Cl^{-} (aq)}\]
Cathode: \[\ce{H2O(l) + e^{-} -> 1/2 H2(g) + OH^{-} (aq)}\]
Anode: \[\ce{Cl^{-} (aq) -> 1/2 Cl2(g) + e^{-}}\]
Overall reaction: \[\ce{NaCl(aq) + H2O(l) -> NaOH(aq) + H2(g) + Cl2(g)}\]
\[\ce{NaOH}\] is a strong base, they turn the brine solution basic and pH will increase.
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