We're learning about single displacement reactions. What happens when Mg + Zn two nitrate reacts? And when Al + Zn two nitrate reacts? Are there colour changes or precipitates formed?

1 answer

Many single replacement reactions are oxidation/reduction reactions and many can be predicted with the help of the activity series. Here is a link to a good activity series table.
http://www.files.chem.vt.edu/RVGS/ACT/notes/activity_series.html
Here is how the activity series works. An element HIGHER in the series will displace an ION of an element LOWER in the series.
Mg(s) + Zn(NO3)2 ==> what happens.
Now look at the chart and notice Mg is ABOVE Zn in the series; therefore the Mg will displace the Zn ION of Zn(NO3)2.
Mg + Zn(NO3)2(aq) ==> Mg(NO3)2(aq) + Zn(s)
You can tell a reaction is taking place because the Mg metal (strip, powder, rod, whatever) disappears and Zn metal (usually finely divided and usually black although Zn is a silvery metal in the normal state and not finely divided).