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Metal Reactivity Series

Middle schoolChemistryA reference-potential displacement model for Mg, Zn, Fe and Cu, with divalent products, explicit limiting amounts and illustrative reaction progress

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About this experiment

Dip a chosen metal into dilute acid, copper sulfate or zinc sulfate and test a prediction about reactivity. Acid can produce hydrogen, while a salt solution can plate a different metal onto the strip. Tracking the remaining and deposited solid shows why an actively reacting strip need not lose total solid mass.

Learning goals

  • Compare metal reactivity using standard reduction-potential differences.
  • Distinguish hydrogen evolution from displacement deposition.
  • Apply mole and mass balances to the reacting strip and solution.

How to use it

  1. 1Dip magnesium, zinc, iron and copper separately into the acid and compare the predicted observations.
  2. 2Test iron in copper sulfate and inspect the copper deposit and changed solid mass.
  3. 3Test copper in zinc sulfate and explain the absence of displacement.
  4. 4Change metal mass and solution amount to find a limiting-reagent plateau, then record the gas or deposit.

The model

Reference displacement feasibility
Mass of the remaining strip and its deposit

Assumptions

  • Metals form divalent ions in this restricted model. Reference reduction potentials in volts are Mg -2.372, Zn -0.763, Fe -0.440 and Cu +0.340, with hydrogen at zero.
  • A reaction is enabled when its reference cell potential is positive. Actual concentration-dependent electrode potentials, oxide films, passivation and kinetic barriers are excluded.
  • The selected metal has a prescribed first-order progress constant. Rate differences are illustrative, not measured rate predictions. Solid mass includes both unreacted starting metal and deposited replacement metal.

Try this in class

  1. Q1Why can a magnesium strip gain total solid mass while magnesium atoms are leaving it?
  2. Q2Why is a standard reference potential not the actual voltage of every selected concentration?

Frequently asked questions

Should every favorable reaction make bubbles?

No. Acid reduction produces hydrogen in this model. Metal-ion displacement forms a solid deposit instead.

Does no visible change prove a real reaction is thermodynamically impossible?

No. Real observations also depend on surfaces and kinetics. This model uses a deliberately restricted standard-potential rule.