Problem 1

A mixture of hydrogen and chlorine kept in a closed flask at constant temperature was irradiated by scattered light. After a certain time the chlorine content had decreased by 20 % compared with that of the starting mixture, and the resulting mixture had the composition: 60 volume % chlorine, 10 volume % hydrogen and 30 volume % hydrogen chloride. (a) What was the composition of the initial gaseous mixture? (b) How are chlorine, hydrogen and hydrogen chloride produced industrially?

Step 3 of 3: Industrial production

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Intuition

At the cathode Na+ is not discharged; water is reduced instead and NaOH accumulates.

\text{anode: } 2\ce{Cl-} -> \ce{Cl2} + 2e^-, \quad \text{cathode: } 2\ce{H2O} + 2e^- -> \ce{H2} + 2\ce{OH-};\quad \ce{H2 + Cl2 -> 2HCl}

Analysis

Industrially, Cl2 and H2 are obtained by electrolysis of aqueous NaCl (brine): Cl2 at the anode and H2 (with NaOH) at the cathode. Hydrogen chloride is then produced by direct combination $\ce{H2 + Cl2 -> 2HCl}$ .