Question

The following substances dissolve when added to water. Classify the substances according to the strongest solute-solvent interaction that will occur between the given substances and water during dissolution.

(1) ion-ion forces
(2) dipole dipole forces
(3) ion dipole forces
(4) london dispersion forces

(A) HF
(B) CH3OH
(C) CaCl2
(D) FeBr3

Answer 1

a) (2)

b) (2)

c) (3)

d) (3)

Step-by-step explanation:

The intermolecular forces are the forces that make molecules to be bond in a substance. When a solvent dissolves a solute, the molecules of the solvent and the solute will be attached by the forces. The types of forces are:

• Ion-ion -> It occurs at ionic compounds, which are formed by the attraction of a cation and an anion. It's the strongest force;
• Dipole dipole -> It occurs at polar covalent compounds. The polarity of the molecule makes that it has partial charges. The positive charge of one molecule will be attached to the negative of the other;
• London dispersion -> It occurs at nonpolar covalent bonds. Partial charges are induced and the attraction happen;
• Hydrogen bond -> It's a kind of dipole dipole force, which is strongest, and it's formed when the hydrogen is bonded to a high electronegativity element (N, O, and F).

The bonds between substances can mix these forces. So if one is polar and the other is nonpolar, the bond will be London dipole; if both are polar, dipole dipole, if one is polar and the other is ionic ion dipole; and if one is nonpolar and the other is ionic, ion London.

Water (H2O) is a polar molecule, so the dipole must happen in all of the dissolutions.

a) HF is a polar molecule, so the bond of it and water will be dipole dipole. In both substances the hydrogen is bonded to high electronegativity elements, so its hydrogen bond! But, because there's no answer to it, we can call it dipole dipole. (2)

b) CH3OH is a polar compound, and have hydrogen bonds, but, as explained above, it'll be dipole dipole forces. (2)

c) CaCl2 is an ionic compound (cation Ca+2 and anion Cl-), thus the force will be ion dipole. (3)

d) FeBr3 is an ionic compound (cation Fe+3 and anion Br-), thus the force will be ion dipole. (3)

Answer 2

Step-by-step explanation:

Ion-ion forces are defined as the forces that exist between oppositely charged ions.

Dipole-dipole interactions are defined as the forces which exist between positive end of polar molecule and negative end of another polar molecule.

Ion-dipole forces are defined as the forces that exist between a charged ion and a polar molecule.

London dispersion forces are defined as the forces that arise due to the development of temporary charges on the combining atoms of a molecule.

Hence, the given substances are classified as follows.

(a) HF - It is a covalent compound but due to the difference in electronegativity of hydrogen and fluorine there will be development of partial charges on both of them.

Hence, in a HF molecule there will be dipole-dipole forces.

(b)
`CH_(3)OH` - There will also be development of partial charges due to the difference in electronegativity of oxygen and hydrogen atoms.

Hence, in a
`CH_(3)OH` there will be dipole-dipole forces.

(c)
`CaCl_(2)` - It is an ionic compound. Hence, there will be partial positive charge on calcium and partial negative charge on chlorine atom.

Hence, in a
`CaCl_(2)` molecule there will exist ion-ion forces.

(d)
`FeBr_(3)` - It is an ionic compound. Hence, there will also exist ion-ion forces.