Major Interaction in Mixtures

Dipole-dipole interaction is a type of intermolecular force that occurs between molecules with permanent dipoles. In mixtures, different types of intermolecular forces can be present, but one force may dominate over the others. The major interaction in a given mixture can be determined by understanding the nature of the molecules present in it.

Explanation

a) KCl and water:
KCl is an ionic compound, which means it has a high electronegativity difference between its constituent atoms. This results in the formation of ions and the presence of ion-dipole interaction with water molecules. However, the strength of this interaction is not as significant as dipole-dipole interactions. Therefore, dipole-dipole interaction is not the major interaction in this mixture.

b) Benzene and carbon tetrachloride:
Benzene is a nonpolar molecule, while carbon tetrachloride is a polar molecule. Although dipole-dipole interaction may occur between these two molecules, the strength of this interaction is not significant enough to be considered the major interaction.

c) Benzene and ethanol:
Benzene is a nonpolar molecule, while ethanol is a polar molecule. Similar to the previous mixture, dipole-dipole interaction may occur between these two molecules, but it is not the major interaction due to the weak strength of this interaction.

d) Acetonitrile and acetone:
Both acetonitrile and acetone are polar molecules, which means they have permanent dipoles. The electronegativity difference between the constituent atoms in these molecules is significant, resulting in a strong dipole-dipole interaction. Therefore, dipole-dipole interaction is the major interaction in this mixture.

Conclusion

The major interaction in a given mixture can be determined by understanding the nature of the molecules present in it. In the case of dipole-dipole interaction, it occurs between molecules with permanent dipoles and can be strong or weak depending on the electronegativity difference between the constituent atoms.