Consider this reaction: Mg(s) + 2H20(1) ► Mg(OH)2(s) + H2(9)

What is the oxidation state of Mg in Mg(s)?

Oxidation state for Mg(s) is 0

Explanation:

This is redox reaction, where one element is oxidized and another is reduced.

H from water is being reduced while the Mg which is in ground state is oxidized.

When the element is reduced, the oxidation state is decreased:

2H⁺ + 2e⁻  ⇄  H₂

When the element is oxidized, the oxidation state is increased

Mg ⇄ Mg²⁺ + 2e⁻

As Mg(s) in the product side, is at ground state, the oxidation state is 0.

Any element in ground state has 0, as oxidation state.

answer: the enthalpy of the overall chemical reaction is +87.88 kj or +88 kj.

according to hess's law, the overall enthalpy of a reaction is the difference between the sum of enthalpy values of all the products and the sum of enthalpy values of all the reactants.

δh(reaction) = ∑nδh(products) - ∑nδh(reactants)

δh(reaction) = [δh +δh] - [δh]

δh(reaction) = [1(-287.02) + 1(0) ] - [1(-374.9)] kj = +87.88 kj

here, δh (pcl3) = -287.02 kj, δh(cl2) = 0, δh(pcl5) = -374.9 kj

therefore, enthalpy of the overall reaction is +87.88 kj or +88 kj.