[Grrr]

Hi everyone,

I'm performing a coulometric rxn in my chemistry class. For one of the electrodes (auxilary, reduction occuring here) we are placing the Pt electrode in a tube (fritted) filled w/ 1 M NaHCO3. I saw bubbles forming at this electrode. I think that these are H2 bubbles but my friend thinks that they are CO2 bubbles. I was wondering if anyone could help me out w/ this.

Looking at the oxidation numbers of H2 & CO2 it leads me to believe that they are H2 bubbles at the electrode. Thanks for you help.

[Donaldson Tan]

why dont u carry a qualitative analysis of the gas to see if it's CO2 or H2.

theoretically speaking, given it's a dilute solution, I would expect H+ to be discharged at the cathode because it's less stable than Na+. Hence H2 gas will be formed.

A bicarbonate solution is alkali in nature. bicarbonate hydrolyeses to produce hydroxide and carbonate ions. The hydroxide ions will be discharged at the anode to produce oxygen gas.