CHEM 112

Question 1

intermolecular forces

Answer 1

weak attractions between SEPARATE molecules that hold them together; NOT bonds

Question 2

types of IMF in order of increasing strength

Answer 2

dispersion, dipole-dipole, hydrogen-bonding, ion dipole

Question 3

What IMF is present in all molecules?

Answer 3

dispersion forces

Question 4

dipole-dipole forces

Answer 4

occur due to unequal sharing of electrons (polar molecules)

Question 5

Dispersion forces are the only IMF present in ________ molecules

Answer 5

nonpolar

Question 6

How does hydrogen-bonding work?

Answer 6

Can only form between a lone pair on N, O, or F in one polar molecule and an H bonded to N, O, or F in another polar molecule

Question 7

ion-dipole

Answer 7

strongest IMF, occurs between ionic compounds

Question 8

Which is the better solvent for NaCl and why? CH3OH or CH3(CH2)5OH

Answer 8

CH3OH- has fewer hydrocarbons
the other molecule is too nonpolar, so it cannot dissolve ionic compounds as well

Question 9

Why do ionic compounds have high conductivity? What about acids?

Answer 9

They dissociate in water, allowing CHARGED ions to move freely

Question 10

How and why does the presence of solute change the vapor pressure and boiling point of a solution as opposed to a pure solvent?

Answer 10

VP decreases, BP increases because solute particles block gas escape

Question 11

Which has a higher conductivity, KNO3 or CaBr2

Answer 11

CaBr2 has more ions (1 Ca and 2 Br), KNO3 has 1 K and 1 nitrate

Question 12

What does Tf represent?

Answer 12

freezing point

Question 13

What is the formula for molar ratio?

Answer 13

X = mol component/total mol

Question 14

What is the formula for molality?

Answer 14

m = mol solute/kg solvent

Question 15

What is the formula for Vant Hoff?

Answer 15

i = mol particle/mol solute

Question 16

What is the van’t Hoff factor?

Answer 16

shows how solutes affect colligative properties of solutions

Question 17

What is the van’t Hoff factor of a covalent compound?

Answer 17

i = 1

Question 18

What is the van’t Hoff factor of an ionic compound or acid?

Answer 18

i = number of particles in compound (ex: HNO3 i = 2, 1 hydrogen, 1 nitrate)

Question 19

intramolecular forces

Answer 19

attractions between atoms WITHIN in a molecule that keep them bonded together

Question 20

covalent bonds vs. IMFs

Answer 20

• covalent bonds share electrons to create strong INTRAmolecular forces inside a molecule; are not broken by phase changes
• INTERmolecular forces create attractions between SEPARATE molecules and CAN be broken by phase changes

Question 21

van der Waals forces

Answer 21

collective term for dispersion, dipole-dipole, and hydrogen bonding

Question 22

The higher the mass of a compound, the _____ its boiling point

Answer 22

higher, larger molecules generally have more IMFs so more heat is needed to disrupt and cause liquid —> gas change

Question 23

The stronger the IMFs of a compound, the _____ its boiling point

Answer 23

higher; need more heat to disrupt IMFs and allow vaporization