29. explain why elements located in the alkali group bond so readily and easily with the
halogens group

Explanation:

Alkali metals are present in group one. All metals have one valance electrons. They need to lose their one valance electron, acquire complete octet and get stable. That's why these re more reactive.

Halogens are present in group seventeen. All halogen elements have seven valance electrons. The need only one electron to complete the octet and gets stable. The halogen readily combine with group one alkali metals. These metal lose their one valance electron which is accepted by halogen atom in this why both complete their octet get stable.

For example:

In sodium chloride electron from sodium is transfer to the chlorine. Sodium becomes positive and chlorine becomes negative ion. Thus both form an ionic compound sodium chloride.

The electronegativity of chlorine is 3.16 and for sodium is 0.93. There is large difference is present that's why ionic compound is formed.

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.