Lecture 2.1

Phase diagram of water - draw

negative slope solid-liquid line When ice melts, molar volume decreases.

Dipole moment formula

u = QxR where Q: charge, and r: distance between charges.

Phase Changes: 1. Solid to liquid 2. Liquid to gas 3. Solid to gas 4. Liquid to solid 5. Gas to liquid 6. Gas to solid

1. Melting (fusion) 2. Vaporisation 3. Sublimation 4. Freezing 5. Condensation 6. Deposition

At an underwater depth of 250 ft, the pressure is 8.38 atm. What should the mole percent of oxygen in the diving gas be for the partial pressure of oxygen in the gas to be 0.21 atm, the same as in air at 1.0 atm?

2.5% O2

Phase Diagram - draw

A graph of pressure versus temperature that shows the conditions under which the phases of a substance exist

Define intramolecular and intermolecular forces.

An intramolecular force is any force that binds together the atoms making up a molecule or compound, not to be confused with intermolecular forces, which are the forces present between molecules

Hydrogen bond

Attractive force between hydrogen atom bonded to very electronegative O,N or F.

Which of the following rare gases effuses twice as fast as Br2, with molar mass 159.8 g mol-1? A. Ne, 20.18 g mol-1 B. Ar, 39.95 g mol-1 C. Kr, 83.80 g mol-1 D. Xe, 131.3 g mol-1 E. Rn, 222 g mol-1

B. Ar, 39.95 g mol-1

Compare the boiling point of methane and carbon tetrachloride. CH4 CCl4

Both are apolar - London forces Cl has more electrons than H - carbon tetrachloride is more polarizable - it has higher Bp

Compare the boiling point of n-pentane and 2,2-dimethylpropane

Both are apolar - London forces n-pentane has bigger surface - stronger London forces -higher Bp

How many moles of methane gas, CH4, (16 g/mol) are in a container with a volume of 448 L at STP? A. 1.2x1024 mol B. 12 mol C. 20 mol D. 2 mol E. 1.2x1025 mol

C. 20mol

A solid characterized by a well ordered structure containing ions is best described as a(n) A. amorphous solid. B. crystalline solid. C. ionic solid. D. molecular solid. E. covalent network solid.

C. Ionic solid

In which of the following are London dispersion forces not the only forces at play? A. Kr B. CH4 C. NH3 D. AlCl3 E. CBr4

C. NH3

The dipole moment of HCl is 1.11 D, and the distance between atoms is 127 pm. What is the percent ionic character of the HCl bond?

If HCl were 100% ionic, a negative charge (Cl) would be separated from a positive charge (H+) by 127 pm. Calculate the expected dipole moment, and compare that calculated value to the actual value. The calculated dipole moment is mu = Q x r =6.09D 1.11/6.09D = 18.2%

What are the major types of crystalline solids?

Ionic, metallic, molecular, covalent network.

Name the types of bonding forces (intramolecular)

Metallic, ionic and covalent bonding

Mole fraction (X)

Moles of solute in solution divided by total number of moles of both solvent and solute

Boyle's Law and constants

P is proportional to 1/V PV=k P1V1=P2V2 Constants: n and T

Guy-Lussac's Law

P is proportional to T P=kT P1/T1=P2/T2

Ideal Gas Law

PV=nRT

A closed flask contains liquid water at 73 oC. The total pressure of air and water vapor mixture is 672 Torr. The vapor pressure of water at this temperature is 268 Torr. What is the partial pressure of the air in the flask?

Pair = Ptotal - Pwater = 672 Torr -268 Torr = 404 Torr

Charge of 1e-

Q = 1.6x10^-19C

Graham's law of effusion

Rate of effusion for a gas is inversely proportional to the square root of its mass, m.

Identify the likely kinds of intermolecular forces in the following substances: (a) HCl (b) CH3CH3 (c) CH3NH2 (d) Kr

Solution (a) HCl is a polar molecule but can't form hydrogen bonds. It has dipole-dipole forces and dispersion forces. (b) CH3CH3 is a nonpolar molecule and has only dispersion forces. (c) CH3NH2 is a polar molecule that can form hydrogen bonds. In addition, it has dipole-dipole forces and dispersion forces. (d) Kr is nonpolar and has only dispersion forces.

What does molecular mass and surface area have to do with the temporary polarisation of a molecule?

The larger the molecular mass and surface area, the greater the temporary polarisation of a molecule. Molecules that are really compact have weaker dispersion forces, whereas ones with long chains feel stronger dispersion forces.

Dalton's Law of Partial Pressures

The total pressure exerted by a mixture of gases in a container is equal to the sum of the pressures of each individual gas in the container. Ptotal = P1+P2+...+Pn

Charles's Law and constants

V is proportional to T V=kT V1/T1=V2/T2 Constants: n and P

Avogrado's Law

V is proportional to n V =kn V1/n1 = V2/n2 where Constants: T and P

Which substance in each of the following pairs would you expect to have the larger vapor pressure at a given temperature. Explain. a) C6H6 or C6Cl6 b) H2C=O or CH3OH c) He or Kr d) H2Se or H2O

a) C6H6 smaller mass, weaker London dispersion forces b) H2C=O no H-bonding c) He smaller mass d) H2Se no H-bonding

Describe the force(s) that must be overcome in converting each of the following substances from liquid to gas state. a) liquid O2 b) Mercury c) CH3I d) CH3-CH2-OH

a) London forces b) Metallic bond c) dipole-dipole d) H-bonding

Name the types of Intermolecular forces

Dipole-diple forces London dispersion forces Hydrogen bonds

A solid characterized by a well ordered structure containing discrete molecules is best described as a(n) A. amorphous solid. B. crystalline solid. C. ionic solid. D. molecular solid. E. covalent network solid.

Discrete means dispersion forces so D. molecular solid

Choose the correct statement about the compounds listed below? tetrachloromethane, tetrabromomethane, tetraiodomethane A. The dipole moment of the compound decreases in the given order. B. Polarizability of the compounds increases in the given order. C. The type of chemical bonding in the compounds are ionic, polar covalent and apolar covalent bonding, accordingly. D. The compounds have about the same boiling point. E. The other statements are not correct.

E.

What is the molar mass of an ideal gas with the density of 7.4 kg/m3 at 298 K and 1.013 MPa? R=8.314 Nm/molK A. 0.018 g/mol B. 18 kg/mol C. 1800 g/mol D. 0.18 kg/mol E. 18 g/mol

E. 18g/mol

Which of the following is an allotrope of carbon? A. Diamond B. Graphite C. Carbon nanotubes D. Fullerene E. All of the above

E. all of the above