In the electrolysis of DILUTE copper(II) sulphate, which cation is discharged at the cathode. Copper(II) or hydrogen. I know that copper(II) ions are more reactive than hydrogen ions, but since this is a dilute solution, shouldn't the hydrogen ions be discharged instead?Is it true that concentration does not affect which cation is discharged? (That's what my classmate said)This actually came out in the exam and the other parts of the same question seemed to hint that I should have put 'copper' as my answer earlier on.
copper is below hydrogen (is less electropositive) in the activity series and so will more readily accept electron at the cathode to be reduced. Only extremes of concentration will affect which ion discharges. The most concentrated ion is most likely to discharge. eg in concentrated brine (sodium chloride), chlorine will be discharged at the anode even though you might normally expect oxygen from the hydroxide ions. For positive ions, the ease of discharge increases in going from those most electropositive to those least electropositive. For negative ions, the ease of discharge increases in going from those most electronegative to those least electronegative.
I'm 99.9 % sure it'll just be the electrolysis of water. The sodium hydroxide will help the water to conduct electricity (it's an electrolyte), but it won't add anything new to be electrolyzed. Water is much easier to reduce than sodium ions, so there will be H2 given off at the cathode, same as in a dilute NaCl solution, and O2 will appear at the anode.
