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Metals with Acid

Summary

Magnesium, mossy zinc and copper foil are reacted with hydrochloric acid to produce hydrogen gas and a salt. The reaction rates are compared.

Hazards

  • Hydrochloric acid is corrosive and toxic.
  • The hydrogen reaction product is flammable.

Chemicals and Solutions

  • Magnesium turnings
  • Mossy zinc
  • Copper foil
  • 3M HCl

Materials

Test tubes, hydrometer cylinders or crystallization dishes, 3 each.

  • Set-up #1: 3 test tubes in test tube rack
  • Set-up #2: 3 hydrometer cylinders
  • Set-up #3: 3 crystallization dishes

Procedure

Add HCl to just more than cover each metal.

Hint: If using the test tube racks or hydrometer cylinders, cover with enough acid (a couple of inches at least) so that the bubbles are obvious, making their up through the solution. The crystallization dishes work well if presenting the demo on the overhead.

Discussion

Many metals react with acids to form salts. Here three acids are placed in hydrochloric acid. Magnesium reacts followed by zinc. Copper does not react fast and will not evolve any visible hydrogen gas during a lecture period.

\( \ce{ Mg_{(s)} + 2HCl_{(aq)} -> MgCl2_{(aq)} + H2_{(g)} } \)

\( \ce{ Zn_{(s)} + 2HCl_{(aq)} -> ZnCl2_{(aq)} + H2_{(g)} } \)

\( \ce{ Cu_{(s)} + 2HCl_{(aq)} -> CuCl2_{(aq)} + H2_{(g)} } \)

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