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?
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).
To determine what happens when Mg reacts with Zn(NO3)2 and Al reacts with Zn(NO3)2, we need to know the reactivity series of metals. The reactivity series is a list that ranks metals in order of their reactivity with other substances.
The reactivity series of metals from most reactive to least reactive is as follows:
Potassium (K), Sodium (Na), Calcium (Ca), Magnesium (Mg), Aluminium (Al), Zinc (Zn), Iron (Fe), Tin (Sn), Lead (Pb), Copper (Cu), Silver (Ag), Gold (Au)
When a metal reacts with a metal nitrate, a single displacement reaction occurs. In a single displacement reaction, a more reactive metal displaces a less reactive metal from its compound.
1. Mg + Zn(NO3)2 → This reaction involves magnesium (Mg) and zinc nitrate (Zn(NO3)2). According to the reactivity series, magnesium (Mg) is more reactive than zinc (Zn). Therefore, magnesium will displace zinc from its nitrate compound. The balanced chemical equation for this reaction is:
Mg + Zn(NO3)2 → Zn + Mg(NO3)2
In this reaction, a colorless and soluble nitrate compound, Zn(NO3)2, is formed. There are no major visual changes or precipitates formed.
2. Al + Zn(NO3)2 → This reaction involves aluminum (Al) and zinc nitrate (Zn(NO3)2). Aluminum (Al) is more reactive than zinc (Zn) according to the reactivity series. Hence, aluminum will displace zinc from its nitrate compound. The balanced chemical equation for this reaction is:
2Al + 3Zn(NO3)2 → 3Zn + 2Al(NO3)3
In this reaction, a colorless and soluble nitrate compound, Al(NO3)3, is formed. Similar to the first reaction, there are no major color changes or precipitates formed.
In summary, when magnesium (Mg) reacts with zinc nitrate (Zn(NO3)2) and aluminum (Al) reacts with zinc nitrate (Zn(NO3)2), the less reactive metal, zinc (Zn), is displaced from its nitrate compound by the more reactive metal magnesium (Mg) or aluminum (Al). The resulting products are soluble nitrate compounds, Magnesium Nitrate (Mg(NO3)2) and Aluminum Nitrate (Al(NO3)3), respectively.