Question

What is the formation reaction of aluminum chloride molecules and its enthalpy of formation?

Answer 1

In order to answer this question, we should know about the chemical formula of Aluminum chloride and as the name indicates that it is composed of aluminum and chlorine elements which clearly shows that it is formed by these two elements.

Complete answer:
First, we should know the chemical formula of aluminum chloride i.e. $AlC{l_3}$ . The compound is formed when aluminum and chlorine react together. The process that produces aluminum chloride, $AlC{l_3}$ from the elemental states of the atoms. This process of the formation of aluminum chloride is an exothermic reaction.
Well we know that chlorine naturally exists as diatomic gas, $C{l_2}\,(g)$ at room temperature ( ${25^o}C$ ) and pressure $1\,atm$ whereas aluminum exists as solid at room temperature ( ${25^o}C$ ) and pressure $1\,atm$ .
The reaction for the standard formation of aluminum chloride is as follows:
$\dfrac{3}{2}C{l_2}(g) + Al(s) \to AlC{l_3}(s)$
Or we can write as,
$3C{l_2}(g) + 2Al(s) \to 2AlC{l_3}(s)$
Also, the enthalpy of formation of aluminum chloride has been found as:
$\Delta H_f^o\, = - 705.63\,\,KJ/mol$
The electronegativity difference of chlorine and aluminum is as follows:
Electronegativity of chlorine $(Cl)$ - Electronegativity of aluminum $(Al)$
$E.N\,(Cl) - \,E.N\,(Al)\, = 3.16 - 1.61 = 1.55$
This indicates that it has the least moderate ionic character in the bonds. Hence, this compound is nonpolar.

Note:
It should be remembered that Aluminum chloride is also referred to as aluminum trichloride or aluminum (III) chloride. The physical appearance of aluminum chloride is white in colour but due to contaminants it gets yellowish in colour. Also, aluminum chloride is a covalently bonded compound. It is also widely used in the production of aluminum metal. It particularly acts as a Lewis acid and is widely used in the various chemical industries.