Chapters 10, 11 & 12

First chem test

linear molecular geometry

• 180 degrees

• ex: BeCl2, HgCl2, CO2

• Orbital: sp

Trigonal planar

• 120 degrees

• ex: BF3, CO3²-, NO3-, SO3

• orbital: sp²

Tetrahedral

• 109.5 degrees

• ex: CH4, PO4³-, TiCl4

• orbital: sp³

sigma bond

A sigma bond is a strong covalent bond formed by overlapping atomic orbitals along the bonding axis, enabling electron sharing between atoms.

pi bond

A pi bond is a covalent bond formed by overlapping atomic orbitals in a side-by-side manner. It occurs when two p orbitals align parallel to each other and share electrons. Pi bonds are found in double and triple bonds, adding stability and strength to the molecule.

Element Be in electron configuration, Molecular orbital configuration, and bond order

bond order formula:

½ (antibonding-bonding)

Element N2 in electron configuration, Molecular orbital configuration, and bond order

unpaired electrons:

attracted

paired electrons:

unattracted

Carbon disulfide, Cs2, has a normal boiling point of 46 degrees celsius and a heat of vaporization of 26.8kJ/mol. What is the vapor pressure of carbon disulfide at 35 degrees celsius in mmh Hg?

Selenium tetrafluoride is a colorless liquid. It has a vapor pressure of 757 mmHg at 105 degrees celsius and 522 mmHg at 95 degrees celsius. What is the heat of vaporization of selenium tetrafluoride?

London Dispersion Forces

• weakest force

• hydrocarbon

• Higher LDF

• Longer the molecular chain = Higher molecular weight

• ex: Ch4

Dipole - Dipole

• H-Cl…H-Cl

• CH3CH2CH3

Hydrogen Bonding

• super dipole

• Only when H is connected to F, O, & N

• ex: H2O

What time of bond is propanol (CH3CH2CH2OH)?

• hydrogen Bonding

• LDF

• Dipole-Dipole

• It has all 3 but hydrogen bonding is the strongest

What type of bonding is methane (CH4)?

• LDF

What type of bonding is fluoromethane (CH3F)

• LDF

• Dipole - Dipole

• It has both but Dipole - Dipole is stronger

Arrange the following hydrocarbons in order of increasing vapor pressure: ethane(C2H6), propane(C3H8), butane(C4H10), hexane (C6H14)

• C6H14 < C4H10 < C3H8 <C2H6

Molecular solid:

• gas elements

• ex: C02(s) = dry ice

Metallic solid:

• just metal elements

• conductors

• Ex: Cu —> 3s3p4s3d

Ionic solid:

• Nonmetal + metal

• insulators

• ex: NaCl, Zns, CsCl

Covalent bonds

• Strongest bond

• can either lose or gain 4e’

• ex: diamond, graphite, asbestos

Classify the following Zinc, Zn according to the forces of attraction that exist between the structural units

• Metallic solid

Classify the following Sodium iodide, NaI according to the forces of attraction that exist between the structural units

• Ionic solid

Classify the following Silicon carbide, SiC according to the forces of attraction that exist between the structural units:

• covalent solid

Classify the following methane, Ch4 according to the forces of attraction that exist between the structural units:

• molecular solid

Arrange the following elements in order of increasing melting point: Silicon, hydrogen, lithium

• H < Li < Si

• The higher the IMF = higher MP

• The higher the MW = higher IMF

Describe what type of solid is formed for each of the following substances and arrange these in order of increasing melting point:

• C2H5OH = Molecular solid, Hydrogen bonding

• CH4 = Molecular solid, LDF

• CH3Cl = Molecular solid, Dipole - Dipole

• MgSO4 = Ionic Solid

• CH4 < CH3Cl < C2H5OH < MgSO4

Solute:

• The smaller amount

• the gas or solid dissolved into a liquid

Solvent:

• The greater amount

Miscible fluids:

• Fluids that mix with or dissolve in each other in all proportions

• ex: Air

Solubility:

• The amount of substance that dissolves in a given quantity of water at a given temperature

Which ion has the larger hydration energy, NA+ or K+?

• Na+

• The higher the radius the smaller the hydration energy, vice versa

A liter of water at 25 degrees celsius dissolves 0.0404 g O2 when the partial pressure of the oxygen is 1.0 atm. What is the solubility of oxygen from air, in which the partial pressure of O2 is 159 mmHg

• 8.44×10^-3 g-L

Mass % of solute:

• the % by mass of the solute contained in a solution

Mass % of solute:

• mass of solute - the mass of solution x 100

ppb =

• 1 mg for every 109g of solution

ppm =

• 1g solute for every 10^6g solutions

Calculate the mass percentage of NaCl in a solution containing 1.50g of NaCl in 50.0g of water.

• 2.91%

Molality =

• moles of solute - kg of solvent

G —> moles

• use when solving for moles

G —> kg

• use when solving for solvent

Toluene, C6H5CH3, is a liquid compound similar to benzene, C6H6. It is starting material for other substances, including trinitrotoluene. Find the molality of toluene in a solution that contains 35.6g of toluene nd 125 g of benzene

What are the mole fractions of glucose and water in a solution containing 5.67g of glucose, C6H12O6, dissolved in 25.2g of water?

A sample with the density of 0.876g/mL contains 5.0g of toluene (C7H8) and 225g of benzene. Calculate the molarity of the solution

White phosphorus, P4, is a white waxy solid melting at 44C to a clear liquid. The liquid has a vapor pressure of 400.0 mmHg at 251C and 760 mmHg at 280C. What is the heat of vaporization of this substance?

• 53.29 kj/mol

mothballs slowly becoming smaller and eventually disappear

• Sublimation

Raindrops hit a cold metal surface, which becomes covered with ice

• Freezing

Rubbing alcohol spilled on the palm of your hand feels cool as the volume of liquid decreases

• Evaporation

List the following substances in order of increasing boiling point: CH3OH, C2H5OH, C2H6, CH4

• CH4 < C2H6 < CH3OH < C2H5OH

Which substance has the lower boiling point: LiCl or HCl

• HCl

Which substance has the lower boiling point: NH3 or PH3

• PH3

In each of the following pair of molecules, which compound experiences the strongest london dispersion force: CCl4 or CF4

• CCl4 because it has a higher molecular weight

Draw a molecular oribital energy diagram for the O2 ion. Write the molecular orbital configuration and determined the bond order for this ion

How much heat is required to vaporize 546.0g of NH3? The heat of vaporization is 23.4 kJ/mol.

7.50×10²kJ

Ethanol (C2H5OH) melts at -114C and boils at 78C. The enthalpy of fusion of ethanol is 5.02 kJ/mol and its enthalphy of vaporization is 38.56 kJ/mol. The specific heats of solid and liquid ethanol are 0.97 and 2.3 J/g*K, respectively. How much heat is required to convert 49.0 g of ethanol at 35C to the vapor phase at 78C

Which hybridization schemes allows for the formation of at least one pi bond: sp³, sp², sp³d²

• sp²

Which hybridization scheme allows the central atom to form more than 4 bonds: sp³, sp³d, sp62

• sp³d