Question

Which of the following explains why the entropy change is greater for the dissolution of NaI compared to the dissolution of NaBr?

A. Iodide has weaker ion-dipole interactions with water than bromide.
B. The interactions between bromide ions with other bromide ions is stronger than the interactions between iodide ions with other iodide ions.
C. The more negative change in enthalpy observed with NaI implies greater dissociation and hence greater entropy.
D. The bromide ion has more negative charge than the iodide ion. Therefore, because of the greater charge, it forms a stronger ion-dipole network with water.
E. The cation forms stronger ion-dipole networks with water in NaBr than NaI because of the weaker bond to Br.

Answer 1

The entropy change for NaI is greater than that for NaBr because iodide ions have weaker ion-dipole interactions with water, leading to a more disordered system and higher entropy upon dissolution.

Step-by-step explanation:

The entropy change is greater for the dissolution of NaI compared to NaBr because Iodide has weaker ion-dipole interactions with water than bromide. This is attributable to the larger size and more diffuse electron cloud of the iodide ion, which makes its interactions with water molecules less specific and weaker compared to the smaller bromide ion. Due to these weaker interactions, when NaI dissolves, there is a greater increase in disorder or entropy within the system as the iodide ions are less constrained by water molecules relative to bromide ions. Since entropy is a measure of disorder or the number of available microstates for a system, the dissolution of NaI leads to a higher increase in entropy.

Answer 2

Answer:Iodide has weaker ion-dipole interactions with water than bromide.

Step-by-step explanation:

The electronegativity difference between sodium and iodine in sodium iodide is about 1.73. This shows that the compound is not composed of purely ionic bonds. Electro negativity decreases down the group hence iodine is far less electronegative than bromine and is thus ineffective in forming strong dipole interactions with water hence the higher entropy due to much less association of ions in solution.