Alkynes do not react directly with aqueous acid as do alkenes, but will do so in the presence of mercury(II) sulfate as a Lewis acid catalyst. The reaction occurs with Markovnikov regiochemistry, so the OH group adds to the more highly substituted carbon and the H adds to the less highly substituted carbon. The initial product of the reaction is a vinyl alcohol, also called an enol. The enol immediately rearranges to a more stable ketone via tautomerization. Draw curved arrows to show the movement of electrons in this step of the mechanism

See explanation and image attached

Explanation:

According to Markovnikov regiochemistry, the negative part of the addendum is joined to the more substituted carbon atom. The addition of H-OH to alkynes occurs in the presence of mercury(II) sulfate as a Lewis acid catalyst.

So, the -OH group is added to the highly substituted carbon and the H adds to the less highly substituted carbon.

The enol produced is shown in the mechanism attached to this answer. Rearrangement of this enol form due to keto-enol tautomerism yields the ketone as shown.

Image credit: chemistry steps

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.