Indicate the type of solute-solvent interaction (Section 11.2) that should be most important in each of the following solutions: $(\mathbf{a}) \mathrm{CCl}_{4}\( in benzene \)\left(\mathrm{C}_{6} \mathrm{H}_{6}\right),(\mathbf{b})\( methanol \)\left(\mathrm{CH}_{3} \mathrm{OH}\right)\( in water, \)(\mathbf{c}) \mathrm{KBr}$ in water, (d) HCl in acetonitrile \(\left(\mathrm{CH}_{3} \mathrm{CN}\right).\)

First, we will determine the polarity of the molecules involved in each solution. Polar molecules have electronegativity differences causing a dipole moment, whereas non-polar molecules do not have any dipole moment. a) CCl₄ (carbon tetrachloride) in benzene (C₆H₆) - CCl₄: Tetrahedral molecule with evenly distributed charges - Non-polar - Benzene: Evenly distributed electron cloud since the molecule is aromatic - Non-polar b) Methanol (CH₃OH) in water - Methanol: Hydroxyl group (OH) renders it polar molecule - Water: High polarity due to electronegativity differences between H and O and its bent structure c) KBr in water - KBr: Ionic compound - Water: Polar molecule d) HCl in acetonitrile (CH₃CN) - HCl: Polar molecule with high electronegativity difference between H and Cl atoms - Acetonitrile: Polar molecule with a triple bond in the cyano group

Now that we have analyzed the polarity of each solute and solvent, let's identify the type of interactions. a) CCl₄ in benzene - Both are non-polar molecules, hence the main type of interaction is London dispersion forces. b) Methanol in water - Both are polar molecules capable of forming hydrogen bonds. Hence, the main interaction type in this solution is hydrogen bonding. c) KBr in water - The ionic compound (KBr) will be solvated by the polar water molecules due to ion-dipole interactions that are most significant in this case. d) HCl in acetonitrile: - Both the solute and solvent are polar molecules. However, HCl has the ability to form hydrogen bonds, but acetonitrile does not. Hence in this case, the most dominant interaction is dipole-dipole forces.