# Electrolysis and reduction potentials [closed]

Why does the hydrogen gets reduced at the cathode and not $\ce{Na}$ when aqueous solution of brine is subjected to electrolysis?

My book says because discharge potential of hydrogen is lower than that of sodium but in the reduction potential table, hydrogen is assigned a value = 0 and sodium a value of -2.7. So isn't the negative value of sodium lesser than that of hydrogen? Or is it being talked just magnitude wise?

Please explain me the whole concept of what factors decide the reduction and oxidation of some elements over others.

## closed as off-topic by Todd Minehardt, ringo, Klaus-Dieter Warzecha, bon, M.A.R. ಠ_ಠMay 22 '16 at 9:52

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• The whole concept of what factors decide how a redox happens is a bit too broad. – M.A.R. ಠ_ಠ May 22 '16 at 9:52

Since $\ce{Na+}$ has a lower reduction potential than $\ce{H+}$, we can expect that $\ce{H+}$ will be preferentially reduced.