In an ionic compound, the size of the ions affects the internuclear distance (the distance between the centers of adjacent ions), which affects lattice energy (a measure of the force need to pull ions apart), which affects the enthalpy of solution. based on ion sizes, rank these compounds by their expected heats of solution. most exothermic to most endothermic. substances are kf kl kbr kcl

Most exothermic

Kl

KBr

KCl

KF

Most endothermic

Explanation:

There is the presence of the same cation in the given salts, so only anion has to be compared.

The charge density of the anion decreases from the fluoride to the iodide as size increases from fluoride to iodide. Fluoride has highest charge density because of the smallest radius in halogen family. Also, potassium fluoride would have highest lattice enthalpy because there will be greater force of attraction between them. The trend for the lattice enthalpy is:

KF>KCl>KBr>KI

Since more energy to split KF , so it will be most endothermic and so on.

So trend is:

KF is most endothermic and KI being most exothermic.

Most exothermic

Kl

KBr

KCl

KF

Most endothermic

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