Concept:During the electrolysis of an aqueous solution, multiple cations migrate to the cathode. The cation with the higher (less negative) reduction potential is preferentially reduced.
Solution:- An aqueous solution of NaCl contains \( Na^+ \) ions from the salt and \( H^+ \) ions from the autoionization of water.
- The standard reduction potential of \( Na^+ \) to Na is \( -2.71 \text{ V} \).
- The reduction potential for the formation of \( H_2 \) gas from water is roughly \( -0.83 \text{ V} \).
- Because \( -0.83 \text{ V} \) is much higher than \( -2.71 \text{ V} \), the Hydrogen ions are preferentially reduced, and \( H_2 \) gas rapidly evolves at the cathode.
Why other options are incorrect:Sodium metal is too reactive to exist in water; it would immediately react even if it did form. Chlorine gas (\( Cl_2 \)) evolves at the anode, not the cathode.
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