Gen Chem 2: Bonding, Intermolecular Forces, Thermodynamics

Question 1

bond dissociation energy (BDE) refers to ?

Answer 1

the energy required to break a bond homolytically, that is where one electron of the bond being broken goes to each fragment of the molecule, creating radical

Question 2

stronger covalent bonds are associated with what 4 thing?

Answer 2

1. shorter bond length
2. higher bond order
3. greater proportion of S character
4. more BDE required to homolytically cleave

Question 3

a coordinate covalent bond refers to ?

Answer 3

when one atom will donate both of the shared electrons in a bond

aka lewis base and ligand

also a nucleophile

Question 4

bond order is determined by

Answer 4

the number of bonds between adjaent atoms. Single ond has bond order of 1 while triple bond has bond order of 3

Question 5

A triple bond would have a BDE of ____ and an r of ____ compared to a single bond with BDE of 83 and R of 1.5

1. 200 and 1.2
2. 64 and 1.7

Answer 5

higher BDE and lower radius, so

1. 200 and 1.2

Question 6

Vapor pressure definition

Answer 6

the pressure exerted by the gaseous phase of a liquid that evaporated from the exposed surface of the liquid.

Question 7

The weaker a substance’s intermolecular forces, the higher/lower its vapor pressure and the more/less easily it evaporates.

Answer 7

higher

more

Question 8

a substance with a high vapor pressure is said to be

Answer 8

volatile

Question 9

the smaller/larger the ions in an ionic solid, the more they are attracted to eachother

Answer 9

smaller

Question 10

what is a network solid?

Answer 10

a lattice of covalent bonds where the only interactions are intramolecular forces.

e.g. diamond

Question 11

types of solids are:

Answer 11

ionic solid: atoms held together by strong anionic and cationic ionic forces e.g. salt

network solid: lattice of covalent bonds being the only forces. e.g. diamond

metallic solids: lattice of nuclei and intter shell electrons surrounded by a cloud of valence electrons that are freely roaming and contribute to metal’s conductivity and malleability

molecular solids: liquids or gases at room temperature because they have a lower boiling point and melting point than the other solids d/t the weak intermolecular forces: hydrogen bonds, dipole-dipole forces, london dispersion forces

Question 12

All metals besides ____ are solids at room temperature

Answer 12

Hg (mercury)

Question 13

a solid at room temp will have a higher/lower melting point?

Answer 13

higher

Question 14

a hydrogen bond acceptor must have:

Answer 14

a oxygen, nitrogen, or flourine atom with an unshared pair of electrons

NOT sulphur!

Question 15

in order to act as a hydrogen bond donor a molecule must have

Answer 15

a hydrogen atom covalently bonded to a nitrogen, oxygen, or flourine atom

NOT sulphur!

Question 16

an induced dipole is an example of inter or intramolecular bonding?

Answer 16

intermolecular

Question 17

a coordinate covalent bond is

Answer 17

a covalent bond formed from a lewis base reaction

Question 18

Zeroth law of thermodynamics

Answer 18

if 2 systems are in thermodynamic equilibrium with a third system then they are in equiliubrium with eachother

e.g. thermometers attempt to reach equiliubrium with their surrounding environment and in doing so, they give a reading of the temperature on the outside of itself

_{menmonic: Zeroth sounds like an egyptian word, which is where pyramids are and this relationship is trangular in nature}

Question 19

First law of thermodynamics

Answer 19

energy is neither created nor destroyed thus the total energy of the universe is constant

Question 20

the thermodynamic universe is:

Answer 20

the system and the surround

Question 21

what factors contribute to change in enthalpy

Answer 21

phase change, formation of stronger intermolecular forces, breaking covalent bonds, temperature

Question 22

ΔH is said with respect to the surround/system?

Answer 22

the system

Question 23

ΔH equation

Answer 23

ΔH_products-ΔH_reactants

Question 24

standard state (ΔH°) specifies:

Answer 24

The standard state temperature is 25°C (298 K). _{Note that temperature is not specified for standard state conditions, but most tables are compiled for this temperature.}

All gases are at 1 atm pressure.

All liquids and gases are pure.

All solutions are at 1M concentration.

The energy of formation of an element in its normal state is defined as zero.

Question 25

Br₂ is a gas/liquid/solid at standard conditions?

Answer 25

liquid

Question 26

I₂ is a gas/liquid/solid at standard conditions?

Answer 26

solid

Question 27

F₂ is a gas/liquid/solid at standard conditions?

Answer 27

gas

Question 28

Cl₂ is a gas/liquid/solid at standard conditions?

Answer 28

gas

Question 29

If there is no change in oxidation state then no oxidation occurs

Answer 29

true.

*This means that when looking at a reaction and deciding whether oxidation has occured, don’t look ONLY at gain or loss of hydrogens, the primary criteria is whether there is a change in oxidation state. For example a

R—C=O-H⁺ → R—C=O would not a change in oxidation state so it is not an oxidation reaction even though there is loss of hydrogens

Question 30

Which of the following relationships are direct or inverse?

1. wavelength and energy

and

2. wavelength and frequency

Answer 30

1. wavelength and energy: inverse
2. wavelength and frequency: inverse

Question 31

A slope on a graph that expresses rate (e.g. y axis= concentration, x axis=time) is constant when the rate is constant.

Answer 31

e.g.