Does ethylene glycol have dipole-dipole forces

Which will have the strongest dipole (a) F2 or HF, (b) CH3Cl or CH3Br? Answer

(a) HF

(b) CH3Cl

Which is more polarizable? (a) Cl2 or I2, (b) C2H6 or C10H22? Answer (a) I2 (b) C10H22

Which of the following materials is likely to have (a) no dipole-dipole forces, but the largest London dispersion forces, (b) the largest dipole-dipole intermolecular forces: I2, He, H2S, H2Te. Answer (a) I2, it is the largest nonpolar molecule. (b) H2S, S is more electronegative and will make the molecule more polar.

What kind of attractive forces must be overcome to (a) sublime At2; (b) vaporize C2H5F; (c) boil hydrogen fluoride, HF; (d) melt LiBr? Explain. Answer (a) Nonpolar - London Dispersion Forces. (b) Polar - Dipole-dipole attractions (and dispersion forces). (c) Very polar - Hydrogen bonds between the molecules. Hydrogen bonds form when hydrogen is covalently bonded to N, O, or F. (d) No molecules, so there are no intermolecular forces - Ionic bonds.

Identify the following crystals (A-E) as ionic, polar-molecular, nonpolar-molecular, covalent (network), or metallic. Explain. There could be more than one or none of the crystal types in the chart.

Crystal	Melting Point (°C)	Boiling Point (°C)	Electrical Conductivity Solid Liquid
A	-83.1	19.54	No	No
B	-259.14	-252.5	No	No
C	1535	3000	Yes	Yes
D	686	1330	No	Yes
E	-56.6	-78.5	No	No
F	-182.48	-164.8	No	No
G	3550	4827	No	No

Answer

A ⇒ good separation between melting and boiling points, relatively high m.p. for molecular, no conductivity - polar-molecular. (HF - polar molecule)

B ⇒ close and low melting and boiling points, no condutivity - nonpolar-molecular. (H2 - nonpolar molecule)

C ⇒ high mp and bp, good conductor - metallic. (Fe - metal)

D ⇒ high melting and boiling points, conducts as a liquid - ionic. (KI - ionic compound)

E ⇒ low and close together mp and bp, nonconductor - nonpolar-molecular. (CO2 - nonpolar molecule)

F ⇒ low and close together mp and bp, nonconductor - nonpolar-molecular. (CH4 - nonpolar molecule)

G ⇒ very high mp and bp, nonconductor - covalent (network). (Diamond - covalent network)

Indicate the type of crystal (ionic, polar-molecular, nonpolar-moleculas, covalent, or metallic) and predict some of the properties (difference in melting and boiling points, conductivity, etc.) for each of the following substances upon solidification: HF, H2, Fe, KI, CO2, CH4, and diamond. Answer

HF - polar molecule, good separation between melting and boiling points, relatively high m.p. for molecular, no conductivity - polar-molecular.

H2 - nonpolar molecule, close and low melting and boiling points, no condutivity - nonpolar-molecular.

Fe - metal, high or low mp and bp, good conductor - metallic.

KI - ionic compound, high melting and boiling points, conducts as a liquid - ionic.

CO2 - nonpolar molecule, low and close together mp and bp, nonconductor - nonpolar-molecular.

CH4 - nonpolar molecule, low and close together mp and bp, nonconductor - nonpolar-molecular.

Diamond - covalent network, very high mp and bp, nonconductor - covalent (network)