Answer: [tex]Na[/tex]
Explanation:
Oxidation reaction : When there is a loss of electrons and thus an increase in oxidation number.
[tex]M\rightarrow M^{n+}+ne^-[/tex]
Reduction reaction : when there is a gain of electrons and thus a decrease in oxidation number.
[tex]M^{n+}+ne^-\rightarrow M[/tex]
Sodium metal has gone under oxidation, as its oxidation state is changing from 0 in [tex]Na[/tex] to +1 in [tex]NaOH[/tex]
[tex]H^+[/tex] ion has gone under reduction, as its oxidation state is changing from +1 in [tex]H^+[/tex] to 0 in [tex]H_2[/tex]
Those chemical agents which get oxidized itself and reduce others is called reducing agents. Thus [tex]Na[/tex] is a reducing agent here.
