Given, the enthalpy of formation of MgCl_((s)) is -125 kJ mol^(-1) and the entahpy of formation of MgCl_(2(s)) is-642kJ mol^(-1). Predict whether MgCl will undergodisproportionnation or not? If yes, calculate the enthalpy of disproportion.

Given, the enthalpy of formation of MgCl_((s)) is -125 kJ mol^(-1) and

1.	Given, the enthalpy of formation of MgCl_((s)) is -125 kJ mol^(-1) and the entahpy of formation of MgCl_(2(s)) is-642kJ mol^(-1). Predict whether MgCl will undergodisproportionnation or not? If yes, calculate the enthalpy of disproportion.
Answer» Solution : Given, (a). `Mg_((s))+(1)/(2)Cl_(2(g))rarrMgCl_((s)) ,DeltaH_(1)^(Θ)=-125 KJ mol^(-1)` (b). `Mg_((s))+Cl_(2(g))rarrMgCl_(2(s)),DeltaH_(2)^(Θ)=-642 kJ mol^(-1)` (C ). Disproportionation of `MgCl` is `OVERSET((1+))(2MgCl_((s)))rarroverset((2+))(MgCl_(2(s)))+overset((0))(Mg),DeltaH_(3)^(Θ)=?` `:.DeltaH_(3)^(Θ)=DeltaH_(2)^(Θ)-2DeltaH_(1)^(Θ)` `=[-642-2(-125)]kJ mol^(-1)` `=-392 kJ mol^(-1)` Since the enthalpy of dispropotionation is exothermic and much higher compared to the formation of `MgCl_((s))`, therefore, `MgCl_((s))` will redily undergo disproportionation reaction. Enthalpy of disproportionationof `MgCl_((s))=392 kJ mol^(-1)`. STATEMENT: Alkani nearth metals do not exhibit an oxidation state of `+3` in their compounds or `MX_(3)` type of compounds are not known. Explanation: For the formation of `M^(3+)` ION, the third electron has to be removed from an INERT gas core, which ishighly stable. `underset(["Noble gas"]ns^(2))(M_((g)))overset(IE_(1))underset(-e^(Theta))rarr underset(["Noble gas"]ns^(1))(M^(o+))overset(IE_(2))rarr underset(["Noble gas"]ns^(0))(M^(2+))` Third third ionisation energy of therse elements is too high to allow the formation of `M^(3+)`. Hence, `MX_(3)` type of compounds are not known.