Relative Reactivities of Metals

Last winter I watched a webinar put on by ACS and AACT called "NGSS in the Chemistry Classroom." As a result of watching that webinar, I took an activity that had NGSS Science & Engineering Practices (SEP) integrated into it and tried it out in class. In this activity, students are required to develop their own procedures and data tables. I provided the materials and equipment and only asked that they present their procedure to me before beginning. For some of the students I encouraged to them rethink their procedures to be more efficient (for example, do we need to react Mg with Mg(NO3)2??), whereas for others, I let them be so we'd have a point of discussion after the lab.

This week I had my current Honors Chemistry 1 students work through the lab. Every student was engaged and appropriately challenged. I posted a photo of a student's well plate on Twitter which led to AACT and another Twitter colleague seeking a copy of the lab for others to use a resource. I wanted to share it here in addition to it being available on AACT's website.


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Comments 1

Bob Worley's picture
Bob Worley | Sun, 12/20/2015 - 04:11

But what about iron?

Yes I know, you have used nitrates for all the solutions and there is no iron(II) nitrate solution readily available. So just switch to another salt such as iron(II) chloride or sulfate. Unfortunately there are problems again as these salts in solution air oxidise to iron(III). Iron(II) solutions are often made in 1M acid solutions and then other reactions mask the displacement reactions. Grrrr.

So why not start from the solid. As an extensions ask the students to add a few crystals of the iron (II) salt to the well-plate followed by 1 ml of water. When you add a tiny bit of magnesium, the coating of iron appears and with a magnet you can make it follow the field. Other metals can be used in other wellplates.

For a sample of iron, you can use a metal paper clip, cut with snippers or little pins, tack, nails( I sure you have a funny name for them in the States). You can then place iron in the series.

But it is really great to show another way of establishing the activity series.

In a Petri dish, place some filter paper and add drops of 0.1M sodium sulfate to the paper to dampen it. Put the magnesium strip on the paper alongside another metal eg, zinc, copper etc. Use a multimeter to establish the voltage obtain when you press on the metals with the electrodes. Investigate the other metals, keeping magnesium as the reference. You can even add aluminium foil to the series.

I had always done this with copper as the reference (read too many books) with very poor resutls. It was only on changing to Mg as the reference that the order became apparent.

The wonderful world of microchemistry ( )!

Merry Christmas to the chemistry teachers of the USA and Canada or as chemists say “Holmium, Holmium, Holmium.”