CHEM 1515 Final Conceptual Review

CHAPTER 12

Intermolecular Forces

Attraction between molecules

Intramolecular forces

Forces within one molecule

Ion-Dipole Attractions

form between ions and polar molecules

Dipole-Dipole Attractions

form between 2 polar molecules

Hydrogen bonding

strong type of dipole-dipole attraction and occurs between hydrogen and F, O or N

What is the importance of hydrogen bonding?

Responsible for the low density of ice and is involved in the helical structure of DNA

How does atomic size affect the strength of dispersion forces?

The larger the atomic size, the stronger the LDF

How does molecular size and chain length affect the strength of dispersion forces?

the larger the size and chain length, the stronger the LDF

How does molecular shape affect the strength of dispersion forces?

Linear shapes have stronger LDF and branched shaped molecules have weaker LDF

Intermolecular forces strongest to weakest

Ion-dipole, hydrogen bonding, dipole-dipole, dispersion

Viscosity

A liquid's resistance to flowing

Surface tension

the tendency of a liquid to minimize its surface due to intermolecular forces

Capillary action

ability of liquid to flow up a tube

Cohesion

attraction between like molecules

Adhesion

attraction between different molecules

Concave meniscus

adhesive forces > cohesive forces; u shape

Convex meniscus

cohesive forces > adhesive forces; horseshoe shape

Vaporization (evaporation)

liquid to gas

Condensation

gas to liquid

Sublimation

solids to gas directly

Deposition

gas to solid directly

Relationship between temperature and vapor pressure

High temperature = High VP (directly proportional)

Relationship between IM forces and vapor pressure

Strong IM forces = Low VP (inversely proportional)

Volatile

evaporates quickly (weak IM forces), and has more gas phase molecules

What temperature and pressures would indicate a substance in a solid phase?

low temperatures and high pressure

What temperature and pressures would indicate a substance in a gas phase?

high temps and low pressure

What temperature and pressures would indicate a substance in a liquid phase?

moderate temperature and pressure

Relationship between atmospheric pressure and boiling point

low atm pressure, low boiling point (directly proportional

CHAPTER 13

What 3 processes occur during solution formation

1. the IM forces between solute particles are broken (endothermic)

2. the IM forces between solvent particles are also broken (endothermic)

3. new IM forces form between solute and solvent particles (exothermic)

Entropy

the degree of randomness or disorder

Saturated solution

a solution that contains the maximum amount of dissolved solute

Unsaturated solution

a solution that contains less solute than max of solute that can be dissolved

Supersaturated solution

a solution that contains more dissolved solute than a saturated solution contains

Crystallization (after saturation)

Raise the temperature and excess solute can crystalize by lowering the temperature

Relationship between solubility of gases and temperature

as solubility of gases decreases, temp increases

Molality

moles of solute/kg of solvent

Osmosis

diffusion of water from low conc to high conc

Nonelectrolytes

do not dissociate in water and dissolve in water as molecules

Electrolytes

either dissociate into ions or ionize in aqueous solution

CHAPTER 14

1st order

rate is directly proportional to concentration ( rate doubles when the conc is doubled)

2nd order

rate is squared (rate quadruples and conc doubles)

Zero order

rate is independent of concentration

5 factors that affect reaction rates

Particle size of solid reactants, concentration, temperature, nature (potential energy) of reactants, presence of a catalyst

what reaction occurs when plot [A] vs time is linear

zero order

what reaction occurs when plot ln[A] vs time is linear

first order

what reaction occurs when plot 1/[A] vs time is linear

second order

what kind of energy diagram shows the reactants with a higher potential energy than the products where ΔH < 0

exothermic

what kind of energy diagram shows the reactants with a lower potential energy than the products where ΔH > 0

endothermic

Relationship between activation energy and rate constant

as activation energy increases, the rate constant decreases

If the molecule has a double bond, will the activation energy be higher or lower?

higher

When can the rate of collisions be increased?

increasing the temperature and the concentration

How do you determine which elementary step is the slow step for the rate-determining step?

the elementary step with the highest activation energy

What are catalysts function?

they lower activation energy which speeds up the reaction

CHAPTER 15

What is the equilibrium constant, K, dependent upon?

the chemical equation and the temperature

K = 1

both reactions are equally favored and at equilibrium

K >> 1

product and forward reaction favored

K << 1

reactant and reverse reaction favored

Q = K

reaction is at equilibrium

Q > K

reaction shifts left (towards reactants)

Q < K

reaction shifts right (towards products)

If A ⇌ B and you add more A, what will happen to the reaction and the comparison of Q and K?

reaction shifts right; Q < K

If A ⇌ B and you add more B, what will happen to the reaction and the comparison of Q and K?

reaction shifts left; Q > K

If A ⇌ B and you remove A, what will happen to the reaction and the comparison of Q and K?

reaction shifts left; Q > K

If A ⇌ B and you remove B, what will happen to the reaction and the comparison of Q and K?

reaction shifts right; Q < K

What happens to the pressure and how does the reaction shift if you decrease the volume of a container of gas?

the pressure increases and the reaction shifts toward the side with fewer moles of gas

What happens to the pressure and how does the reaction shift if you increase the volume of a container of gas?

the pressure decreases and the reaction shifts toward the side with more moles of gas

For endothermic reactions where ΔH > 0 what happens to the change in K, the Q vs K, and the reaction shift when T increases?

K increases, Q < K, and the reaction shifts right

For endothermic reactions where ΔH > 0 what happens to the change in K, the Q vs K, and the reaction shift when T decreases?

K decreases, Q > K, and the reaction shifts left

For exothermic reactions where ΔH < 0 what happens to the change in K, the Q vs K, and the reaction shift when T increases?

K decreases, Q > K, and the reaction shifts left

For exothermic reactions where ΔH < 0 what happens to the change in K, the Q vs K, and the reaction shift when T decreases?

K increases, Q < K, and the reaction shifts right

CHAPTER 16

Arrhenius acid

increase H+ ion conc

Arrhenius base

increase the OH- ion conc

7 strong acids

HCl, HBr, HI, HNO3, H2SO4, HClO3, HClO4

Strong base categories

OH- with group 1 or 2 element

Bronsted acid

proton (H+) donor

Bronsted base

proton acceptor

The stronger the acid, the ________ its conjugate base

weaker

Acid strength compared to bond energy

inversely related

Acid strength compared to anion size and electronegativity

directly related

2 things that affect bond strength?

size of anion and electronegativity

Acid strength compared to Ka and pKa

Ka: directly related

pKa: inversely related

Lewis acid

electron pair acceptor

Lewis base

electron pair donor

CHAPTER 17

Buffer

a solution that resists a change in pH even when an appreciable amount of of acid/base is added

Strong acid with strong base titration

initial pH: pH = -log[H3O+]

half-equivalence point: the amount of acid (or base titrated); pH = -log[H3O+]

equivalence point: pH = 7

after equivalence point: convert excess OH- to moles

Strong base with strong acid titration

initial pH: pOH to pH = 14 - pOH

half-equivalence point: (1) calculate the moles of base before adding acid, (2) calc moles of acid added, (3) use ICE table to find [OH-] and calc pH

equivalence point: pH = 7

after equivalence point: calc moles of acid [H3O+] added after equivalence point

Weak acid with strong base titration

initial pH: pH = -log√Ka⋅[HA]

half-equivalence point: pH = pKa

equivalence point: pOH = -log√Kb⋅[A-] and then pH = 14-pOH

after equivalence point: excess OH-; pOH = -log[OH-] and convert to pH

Weak base with a strong acid titration

initial pH: pOH = -log[OH-] and convert to pH

half-equivalence point: pH = pKa

equivalence point: calc moles of conj acid where mol of strong acid = mol of weak acid

after equivalence point: excess H3O+ moles and conc with total volume

Relationship between the solubility product constant (Ksp) and the solubility

directly related

Molar solubility

number of moles of a substance that can dissolve in 1L (solve for x)

A common ion can ______ the solubility of an ionic compound in solution

suppress

Q < Ksp

solution is not saturated

Q = Qsp

solution is saturated and at equilibrium

Q > Ksp

solution is supersaturated and will precipitate until Q = Ksp