The Naked Scientists

The Naked Scientists Forum

Author Topic: Electrolysis - In electroplating, specifically zinc plating....  (Read 6352 times)

Offline abdillah

  • First timers
  • *
  • Posts: 9
    • View Profile
In electrolysis, we know that for the discharge of cations in aqueous solutions, it is according to their position in the metal reactivity series.

Hence in electroplating, if I have zinc as my anode in a zinc solution and copper metal as my cathode. In theory, the zinc anode will dissolve and form Zn2+ ions. However, at the cathode, hydrogen ions will be discharged and hydrogen gas will be given off. However, there are cases of zinc electroplating in industrial applications.

How does that work? Are there other factors to what cations will be discharged?

Please help, I'm teaching junior high school students (in my country we call then secondary students) these concepts and they are asking whether it is possible to plate with metals that are above hydrogen...

Regards,
in dire straits Chem. teacher


 

Offline Hikazori

  • First timers
  • *
  • Posts: 4
    • View Profile
Actually, for a zinc/copper voltaic cell, the zinc solid does dissolve to form more Zn^2+ ions, but the movement of electrons causes the Cu^2+ ions to deposit onto the copper cathode. Hydrogen is not involved in this particular cell, so I'm not sure what you mean by the liberation of hydrogen gas in the reaction, unless you're talking about a different cell.

The cell notation for this reaction is Zn|Zn^2+||Cu^2+|Cu, and the standard cell voltage for the cell is +1.10 volts.
 

Offline Hikazori

  • First timers
  • *
  • Posts: 4
    • View Profile
You might be referring to the golden penny experiment, in which copper pennies in contact with granular zinc in a solution of 1M NaOH form a layer of zinc metal on them. This reaction does involve the liberation of some Hydrogen gas in the reaction Zn + 2OH-+2H2O --> Zn(OH)42-+ H2.
 

Offline abdillah

  • First timers
  • *
  • Posts: 9
    • View Profile
thanks for the replies, but it still does not answer my question.

hikazori, I'm not referring to the zinc/copper voltaic cell or the copper penny experiment.

I'm referring to the process of electroplating. I'm wondering if I use aqueous solutions of zinc (or even chromium), wouldn't hydrogen be given off instead of zinc? This is because of the position of zinc in the metal reactivity series. Thus hydrogen ions will be more easily discharged as compared to zinc?

 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8669
  • Thanked: 42 times
    • View Profile
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums