Lower secondary · 15 min

Activity series: zinc versus copper

Dip a zinc strip into blue copper sulfate and watch red copper grow while the blue fades.

Goal

Show that zinc is more reactive than copper by observing the displacement reaction $\ce{Zn + Cu^{2+} -> Zn^{2+} + Cu}$ .

Apparatus and reagents

Virtual beaker with $\ce{CuSO4}$ solution and a zinc strip; a slider sets how deep the strip is immersed.

Procedure

Start the simulation and note the initial blue colour of the $\ce{CuSO4}$ solution.
Increase the immersion slider and watch red-brown grains of copper appear and sink around the immersed part.
Wait and compare: the deeper and longer the contact, the more copper deposits and the paler the solution becomes.

What to observe

A red-brown copper deposit forms on the zinc surface while $\ce{Zn^{2+}}$ ions pass into solution.
The blue colour of $\ce{Cu^{2+}}$ gradually fades as the ions are consumed.

Explanation

Zinc gives electrons more easily than copper: $\ce{Zn}$ is oxidised ( $\ce{Zn -> Zn^{2+} + 2e^-}$ ) and $\ce{Cu^{2+}}$ is reduced to metal ( $\ce{Cu^{2+} + 2e^- -> Cu}$ ). A metal higher in the activity series always displaces a less reactive metal from its salt solution — the basis of the series $\ce{K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag > Au}$ .

Chemists behind it

Michael Faraday