How can the speed of solvent molecules be slowed down?

Explanation:

The speed of molecules increases when temperature is increased as it will result in more number of collisions between the molecules. Thus, there will be  increase in kinetic energy of molecules and increase in the speed of solvent molecules.

Whereas on decreasing the temperature, the kinetic energy of molecules will decrease. This will result in less number of collisions between the molecules. Therefore, the speed of solvent molecules will slow down.

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.

the answer would be b i believe