12 pts) 21. Which ion-dipole interaction below results in the smallest (less neg

Question

12 pts) 21. Which ion-dipole interaction below results in the smallest (less negative) hydration energy? water Li water Na water Provide a brief explanation for your answer. [2 pts! 22. Indicate the main type of intermolecular force (ion-dipole, dipole-dipole, hydrogen bonding. dispersion) that must be overcome in order to: 14x2 pts (i) melt solid ice (i) evaporate liquid benzene (CeHe) (ill) evaporate water from salt water (iv) sublime solid iodine 2n o ote b aheaelow. How many hentum atoms are present in ne unt cer Show your calculations in the space provided. 14 pts] Rhenium

Explanation / Answer

1. Hydration energy is the energy released when 1 mol of a substance is dissolved into a solution.
It is always negative, as bonds (e.g. dative, ion-dipole) are being formed. When the solvent is other than water the process is referred to as solvation..
The enthalpy change of a solution is equal to the sum of three different energy transfer processes
first is the lattice energy, the second is enthalpy change of hydration of cation and the third is the
enthalpy change of hydration of anion. By definition, the enthalpy change of hydration Delta H hyd is the enthalpy change that takes place when 1 mole of gaseous ion is dissolved in excess water to make one mole aqueous ion. The relationship depends on the charge density of the ions being hydrated - Higher charge density, more exothermic reaction and higher hidration energy.

So the answer is c) K+ because it has least charge density.

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