Identify the predominant intermolecular forces in each of these substances.

Note: If you answer any part of this question incorrectly, a single red X will appear indicating that one or more of the phrases are sorted incorrectly.

1.

H

2

O

2.

C

a

C

l

2

3.

C

H

3

C

H

(

C

H

3

)

O

H

4.

C

H

4

5.

N

H

3

1. Hydrogen bond

2. Ion-ion

3. Hydrogen bond

4. London force

5. Hydrogen bond

Explanation:

Intermolecular forces are the ones that keep the molecules, or ions, together in the substance. If the substance is metal then, metallic forces are involved in it; if it's an ionic compound, then ion-ion forces are involved in it, and, if the compound is a molecule, it may have 3 different types of forces.

The force depends on the polarity of the molecule, which is given by the measure of the dipole moment. If the dipole moment is 0, the molecule is nonpolar, and if it's different from 0, it's polar. The polarity is given by the dipole moment, which is the vector sum of the dipoles of the bonds. The dipole is the difference of electronegativity between the elements of the bond.

The nonpolar molecules have a London force, which is the weakest force. The polar molecules have dipole-dipole forces, and, if the dipole is formed by hydrogen and a high electronegative element (N, O, or F), the dipole-dipole is extremely strong and it's called a hydrogen bond.

1. The water is a polar molecule because it has angular geometry, so, the dipole of the O-H bond is not canceled. Because it has the bond between H and O, the force is hydrogen bond.

2. CaCl2 is an ionic compound formed by the ions Ca+2 and Cl-, so the force is ion-ion.

3. CH3CH (CH3) OH has a polarity at the O-H bond, so as the water it has hydrogen bond.

4. CH4 has a tetrahedral geometry, and the dipole of the C-H bonds are canceled, so it's a nonpolar molecule with the London force.

5. NH3 has a pyramid trigonal geometry, and so the dipole of N-H is not canceled, so it's polar and has the bond of H with N, so, it has hydrogen bond force.