Exam 1

The molar heats of sublimation and fusion of iodine are 62.3 kJ/mol and 15.3 kJ/mol,respectively. Calculate the molar heat of vaporization of liquid iodine.

47 kJ/mol DHfusion + DHvaporization = DHsublimation DHvaporization = DH sublimation - DHfusion DHvap= 62.3-15.3

how many basic unit cells are there?

7

Which of the following properties indicates the presence of strong intermolecular forces in a liquid? A)a low vapor pressure B)a low critical temperature C)None of the above. D)a low heat of vaporization E)a low boiling point

A

Which of the following characteristics indicates the presence of weak intermolecular forces in a liquid? A) a high boiling point B) a low heat of vaporization C) None of the above. D) a low vapor pressure E) a high critical temperature

B

Which of the following is expected to have the highest normal boiling point? H2 Br2 O2 N2 F2

Br2 because it is the largest

Butter melts over a range of temperatures, rather than with a sharp melting point. Butter is classified as a/an A)covalent solid. B)ionic crystal. C)amorphous solid. D)metallic crystal. E)molecular crystal.

C

Charcoal is classified as a/an A)ionic crystal. B)metallic crystal. C)molecular crystal. D)amorphous solid. E)covalent solid.

C

which of the following is expected to have the highest normal boiling point? C2H6 C3H8 C5H12 C4H10 CH4

C5H12 -> it's the largest molecule

Which of the following is expected to have the lowest normal boiling point? C2H6 C3H8 C5H12 C4H10 CH4

CH4 -> the smallest molecule

Which substance would have the smallest molar heat of vaporization? C4H10 C5H12 C3H8 CH4 C2H6

CH4 is the smallest -> weaker intermolecular force

What type(s) of intermolecular forces exist between the following pairs? HBr and H2S

Dipole-Dipole

Which pure substance would have the largest molar heat of vaporization? Ar H2 N2 H2O CH4

H2O has hydrogen bonding -> stronger intermolecular force

Which of the following is expected to have the highest normal boiling point? HF HCl HBr HI HAt

HF -> Florine is the most electronegative -> strongest intermolecular forces

molecular crystal

Held together by H-bonding, dipole-dipole dispersion forces Low melting point Soft No conductivity

The intermolecular forces present in CH3CH2NH2 include which of the following? I. dipole-dipole II. ion-dipole III. dispersion IV. hydrogen bonding

I., III., IV.

an example of a covalent network solid is:

a diamond

hydrogen bonding

a special dipole-dipole interaction between hydrogen atoms in polar N-H, O-H, F-H bonds AND have a lone pair on the N, O, or F

dipole-dipole forces

attractions between oppositely charged regions of polar molecules

ion-induced dipole

cation or anion causes a neutral atom (non-polar) to become temporarily polar by unevenly distributing the electrons within the cloud

does viscosity increase or decrease with increasing temperature?

decreases

The solubility of gases in water usually increases with

decreasing temperature and increasing pressure

Soot collecting on the inside of a chimney is an example of which phase transition?

deposition gas -> solid

What type(s) of intermolecular forces exist between the following pairs? NH3 and C6H6

dipole-induced dipole

boiling point elevation and vapor pressure lowering are _______ proportional to the molal concentration of solute species:

directly

freezing point depression and molality are ____ proportional

directly

electronic geometry vs molecular geometry

electronic geometry describes the spatial arrangement of all pairs of electrons around the central atom, both bonding and lone pairs molecular geometry describes the spatial arrangement of only the bonding pairs of electrons ex. NH3 electronic G= tetrahedral molecular G= trigonal pyramidal

Which phase changes are exothermic?

freezing, condensation, deposition

Rank the states of matter from weakest to strongest intermolecular forces.

gas < liquid < solid

deposition

gas to solid

greater intermolecular forces = ______ boiling point

greater

if there is a positive slope, the density of the state on the left will be _____ than the state on the right

greater ex: solid carbon is more dense than liquid carbon

if there is a negative slope, the density of the state on the right will be _____ than the state on the left

greater ex: water is more dense than ice

covalent solids

high melting point hard poor conductor of heat and electricity

ionic solids

high melting point hard but brittle as a solid is a poor conductor of heat and electricity as a liquid is a good conductor of electricity

the larger the molecule, the ________ it's viscosity

higher

the lower the freezing point, the _____ the delta T (change in freezing/melting point)

higher

What type(s) of intermolecular forces exist between the following pairs? Cl2 and HBr4

instantaneous dipole-induced dipole

ion-dipole forces

ion bonding to polar molecules

What type(s) of intermolecular forces exist between the following pairs? I2 and NO3-

ion-induced dipole

what types of molecule experiences larger dispersion forces?

larger and heavier atoms and molecules exhibit stronger dispersion forces

the higher the molality, the _____ the freezing point

lower

adding a nonvolatile solute to a solution _____ the freezing point

lowers

adding a nonvolatile solute to a solvent

lowers the solutions vapor pressure making the water boil hotter

Which phase changes are endothermic?

melting, vaporization, sublimation

crystalline solid

particles are arranged in a definite repeating pattern

dipole-induced dipole

polar molecule when placed next to a non-polar molecule temporarily creates an induced charge within the non-polar molecule

What is the result of a force distributed over an area?

pressure

during osmosis, what passes through a membrane?

pure solvent

strong intermolecular forces = ______ vapor pressure

smaller

metallic crystals

soft or hard low or high melting point good conductor

sublimation

solid to gas

amorphous solid

solids that lack an ordered internal structure melts over a wide range of temperatures rather than a sharp melting point

strong or weak intermolecular forces have a greater sufrace tension?

strong

strong or weak intermolecular forces have a high boiling point?

strong

What factors affect the pressure of an enclosed gas?

temperature

what is viscoity?

the resistance of a liquid to flow greater resistance = greater viscosity

if there is a negative deviation to raoult's law, then:

the solvent-solute interaction is stronger than the solvent-solvent interaction and the solute-solute interaction

if there is a positive deviation to raoult's law then"

the solvent-solvent and solute-solute interaction are stronger than the solvent-solute interaction

in terms of x-ray diffraction patterns, what is the difference between a natural diamond and a man-made/synethetic one

there is no difference

instantaneous dipole-induced dipole

two non-polar molecules next to each other creates an instantaneous dipole in a molecule and can cascade down a system