Simple exchange reactions in between metals they are chemical phenomena which can only occur when a simple substance, which must be a metal, is placed in the same container as a compound substance.
Conventionally, the simple exchange reaction between metals it is also called the displacement reaction. This is because the metal (A) of the simple substance changes position with the cation (Y) of the composite substance (YC), as represented in the following generic equation:
A + YC → AC + Y
However, the simple exchange reaction between metals occurs only if the simple metallic substance is more electropositive, that is, more reactive than the cation present in the compound.
To help, below is a scheme containing the descending order of electropositivity of the main chemical elements that participate in simple exchange reactions between metals:
In descending order of electropositivity, we emphasize the noble metals
In that order, the element lithium has the highest electropositivity, while the element gold has the lowest. All elements located below hydrogen are called noble metals.
Note: Noble metals are those with very low electropositivity, that is, the chemical reaction capacity of these metals is very limited. Generally speaking, a noble metal would only be able to displace another noble metal.
1st Example: Reaction between metallic copper and hydrochloric acid.
Ass(s) + HCl → Does not occur
That simple exchange reaction it does not occur because aluminum is a metallic element that is less electropositive than the sodium cation present in the composite substance, and is therefore not capable of displacing it.
2nd Example: Reaction between metallic aluminum and sodium bromide (NaBr).
Al(s) + NaBr → Does not occur
That simple exchange reaction it also does not occur because aluminum is a metallic element that is less electropositive than sodium cation (Na+), present in the compound, which makes it unable to displace it.
3rd Example: Reaction between potassium and copper sulfate II.
K + CuSO4 →
That simple exchange reaction it occurs because potassium is a more electropositive metallic element than copper. Thus, potassium displaces copper, generating the following changes:
- Transformation of copper into the simple substance Cu;
- Formation of the salt called potassium sulfate (K2ONLY4), resulting from the union of potassium (which has a +1 charge, as it belongs to the IA family) with the sulfate anion (SO4-2).
The following is the balanced equation that represents this process:
2K(s) + CuSO4 → Cu(s) + K2ONLY4
4th Example: Reaction between metallic magnesium and iron chloride III.
Mg + FeCl3 →
THE simple exchange reaction it occurs because magnesium is a more electropositive metallic element than iron. Thus, magnesium displaces iron and generates the following changes:
- Transformation of iron into the simple substance Fe;
- Formation of the salt called magnesium chloride (MgCl2), resulting from the union of magnesium (which has a +2 charge, as it belongs to the IIA family) with the chloride anion (Cl-1).
The following balanced equation represents this process:
3 mg(s) + 2 FeCl3 → 2 Fe(s) + 3 MgCl2
5th Example: Reaction between aluminum and sulfuric acid.
That simple exchange reaction it is because aluminum is a more electropositive metallic element than hydrogen. Thus, aluminum displaces hydrogen and generates the following changes:
- Transformation of hydrogen into the simple substance hydrogen gas (H2);
- Formation of the salt called aluminum sulfate [Al2(ONLY4)3], resulting from the union of aluminum (which has a +3 charge, as it is from the IIIA family) with the sulfate anion (SO4-2 ).
The following is the balanced equation that represents this process:
2 Al(s) + 3 H2ONLY4 → 3 H2(g) + Al2(ONLY4)3
By Me. Diogo Lopes Dias
Source: Brazil School - https://brasilescola.uol.com.br/quimica/reacoes-simples-troca-entre-metais.htm
