Polarity and Intermolecular Forces

Question 1

CF₂Cl₂ is a common freon used in refrigerators. The strongest intermolecular forces holding these molecules together are:

Answer 1

Dipole-Dipole forces

Slightly polar molecule since fluroine is more EN than chlorine.

Question 2

Which of the following molecules has the greatest dipole moment?

A. SO3

B. H2O Correct Answer

C. SiCl4

D. CO2

Answer 2

H2O

EN of O is producing overal moment toward O.

Question 3

Each of the following pairs of substances interact through van der Waals forces EXCEPT:

A. Na+ and H2O

B. HCl and Ar

C. Cl2 and Br2

D. NH3 and H2S

Answer 3

Na+ and H2O

VDW forces interact only between neutral atoms

Question 4

Which of the following molecules contains the most polar covalent bond?

A. CH4

B. H2O

C. NaCL

D. HF

Answer 4

HF

Most polar covalent bond. F is more EN that O or C. NaCl is ionic, not covalent

Question 5

At room temp, H2S is a gas, H2O is liquid. Which of the following plays an important role in this observation?

A. The electronegativity of oxygen is greater than that of sulfur.

B. Sulfur has a greater ionization energy than oxygen has.

C. Sulfur has a smaller atomic radius than oxygen.

D. Stronger hydrogen bonds form between molecules of hydrogen sulfide than between molecules of water.

Answer 5

A. The EN of O is > S

Question 6

The BeCl2 molecule is

A. linear and polar.

B. bent and nonpolar.

C. linear and nonpolar.

D. bent and polar.

Answer 6

C. Linear and nonpolar

CL on either side of Be, so liner, and EN cancels out

Question 7

Which of the following molecules has the lowest boiling point?

A. F2

B. Cl2

C. H2O

D. HCN

Answer 7

A. F2

Weakest intermolecular force. F2 and Cl2 have only london dispersion, and F2 is smaller.

Question 8

Which mixture of molecules will have the strongest interactions?

A. F2/Cl2

B. Cl2/NH3

C. CH3I/H2O

D. NH3/H2O

Answer 8

D.

Identify intermolecular forces of each component, then the forces between components. D has hydrogen bonding individually and with each other.

Question 9

SDS has a highly charged head and long hydrocarbon tail. SDS increases a proteins solubility in water, which forces are responsible for this?

A. Dipole-Dipole

B. Hydrogen Bonding

C. Ion-Dipole

D. London Dispersion forces

Answer 9

D.

LD predominates with nonpolar molecules. The hydrocarbon tail, which interacts with the protein, is nonpolar.

Question 10

Which of the following compounds displays the lowest vapor pressure at 15 Celcius?

A. NH3

B. CO2

C. SO2

D. HF

Answer 10

D

Least vapor pressure is associated with strong intermolecular force. NH2 and HF both form Hbonds. HF more polar and greater weight.

Question 11

All of the following are examples of polar molecules except:

A. CCl4-

B. HF

C. CO

D. H2O

Answer 11

A

Dipole moments are all cancelled out

Question 12

Among the following, which molecular geometry CANNOT result in nonpolar structure?

A. Bent

B. Diatomic Covalent

C. Square planar

D. Trigonal planar

Answer 12

A

Bent cannot be nonpolar. Only symmetrical molecules can be nonpolar.

Question 13

The vapor pressure of liquid 1 is greater than liquid 2. Which is true of liquid 1?

A. Stronger IM forces than L2

B. Higher heat of fusion than L2

C. Higher heat of vaporization thatn L2

D. Boils at lower temp than L2

Answer 13

D

Boiling=vapor pressure equaling atmospheric. Higher vapor pressure means lower boiling point due to weaker bonds.