chem final 1120

nucleophile

electron rich

electrophile

electron lacking

chilarity

connected to 4 different centers

rank the carbocation stability from most → least stable

3 > 2 > 1 > CH bonds

Sn1 reactions

rate = ?

__ step reaction

• what are the steps?

overall reaction order = ?

• substrate = ?

• nucleophile = ?

rate = k [substrate]

two step reaction

• Leaving group leaves (step 1)

• carbocation leaves (step 2)

overall reaction order = 1st

• substrate = 1st order

• nucleophile = 0th order

Sn2 reactions

rate = ?

__ step reaction

• what are the steps?

overall reaction order = ?

• substrate = ?

• nucleophile = ?

rate = k [substrate][nucleophile]

one step reaction

• LG & carbocation leaves at same time

overall reaction order = 2nd

• substrate = 1st

• nucleophile = 1st

1st order reactions

• how do you determine?

• what is the rate equation?

• what is the unit?

• what is the graph?

• if one concentration gets an increase of x2, x3, etc, then the initial rate will be affected in the same manner = x2, x3, etc

  • EX: [BrO3]= x2 & Rate= x2

• rate= k[A]¹

• unit: s^-1

• graph = ln[R]

  • linear

2nd order reactions

• how do you determine?

• what is the rate equation?

• what is the unit?

• what is the graph?

• if one concentration gets an increase of x2, x3, etc, then the initial rate will be affected by a more of an increase = x4, x6, etc

  • EX: [BrO3]= x2 & Rate= x4

• rate= k[A]²

• unit: M^-1s^-1

• graph = 1/[R]

  • exponential

0th order reactions

• how do you determine?

• what is the rate equation?

• what is the unit?

• what is the graph?

• if one concentration gets an increase of x2, x3, etc, then the initial rate will NEVER be affected

  • EX: [BrO3]= x2 & Rate= x1

• rate= k

• unit: M/s

• graph = [R]

  • straight

oxidative states for a elementary substance = O₂ , Cl₂ , H₂ , etc

always 0

oxidized & reducing agent

what does this mean for the oxidative state

lose e^-

oxidative state: INCREASE

• ex = 0 → +1

reduction & oxidizing agent

what does this mean for the oxidative state

gain e^-

oxidative state: DECREASE

• ex = 0 → -1

is anode oxidation or reduction

oxidative

is cathod oxidation or reduction

reduction

how to use cell voltage

Vc - (Va) = Δ V

if ΔV > 0, what does this mean

its POSITIVE (+)

spontaneous which means its better for reducing

if ΔV < 0

its NEGATIVE (-)

non-spontaneous, which means its not good for reducing

• oxidative

what weakens a base vs strengthens

weak- e- withdrawing (OH group close to NH), high electronegativity, resonance

strength - e- donating (CH group close to NH), low electronegativity, inductive

how to tell if reaction is PF vs RF

PF = strong —> weak

RF = weak —> strong

if a question gives molarity, pH/Ka what should you do

ICE TABLE

-then the assumption method = concentration / Ka > 400

more acidic =

bigger sixes & large EN

rate of the foward reaction depends on what

products

rate of reverse reaction depends on what

reactants 

relationship between pH and pKa @ equivilance point

pH = pKa at 50 

more basic

less electronegativity + lone pair of e-

pH and pKa

pH ~ pKa

pH —> pOH

14 = pH + pOH

pH —> [H3O+]

10^-ph = [H3O+]

[H3O+] —> pH

pH = -log[H3O+]

small pKa

big pKa

small = strong acid

big = weak acid

Ka equation

Ka=[A-][H3O+]/[HA]

thermodynamic argument 

kinetic argument

thermo - @ equilibrium

kinetic - rate of forward v rate of reverse

large rate of forward > small rate of reverse shift towards…

shift toward PRODUCTS

small rate of forward < large rate of reverse shift towards…

shift toward REACTANTS

relative abundance equation

pH = pKa + log [A-]/[HA]

which species would be found in this pH

if the pH’s are LESS than the pKa = it will be found in this area

buffer

weak acid + weak base

only differ by 1 proton

oxidation equation

A —> A^n+ + ne-

reduction equation

B^m+ + me- —> B

mnemonic for cathode and anode

AN OX (oxidation = anode) carried electrons to a RED CAT (reduction = cathode)

what is the anode in the salt bridge

Zinc

what is the cathod in the salt bridge

copper

what is the salt bridge doing

salt bridge doesnt disrupt equilibrium because it creates a closed circuit that helps electrons run thru to get to teh cathode side

rate law

rate = k [A][B]..

how to find intermediate

produced then consumed

how to find overall reaction

reaction WITHOUT intermediates

k =

Ae^(-Ea/RT)

given TWO temps equation

e^(-Ea/R)(1/T2 - 1/T1)

what does a catalyst (enzyme) do

consumed then produced

rate average equation

[A2] -[A1] / ( t2 - t1 )

how would you find the rate of decomposition

rise/run ==> SLOPE

What is a 0th order reaction, and how does its rate depend on the concentration of reactants?

• 0th order reaction is a reaction whose rate is independent of the concentration of the reactant(s).

• Rate law: Rate= k (k = rate constant)

• Concentration vs. time: decreases linearly over time:

  [A]=[A]0−kt[A] = [A]_0 - kt[A]=[A]0​−kt

• Half-life: t1/2=[A]02kt_{1/2} = \frac{[A]_0}{2k}t1/2​=2k[A]0​​ (depends on initial concentration)

what graph is this: 0, 1, 2 order

0th order

what graph is this: 0, 1, 2 order

1st order

what graph is this: 0, 1, 2 order

1st order

what graph is this: 0, 1, 2 order

2nd order

What are the key features of a first-order reaction?

• Rate law: Rate=k

• Units of k: s−1

• Graph: Straight line when plotting ln⁡[A] v t

What are the key features of a second-order reaction?

• Rate law: Rate=k[A]^2 OR Rate=k[A][B]

• Units of k: M−1s−1

• Graph: Straight line when plotting 1/[A] vs. t

half life of 1st order reaction

ln(2)/t1/2

given three graphs: [R], ln[R], or 1/[R]

two graphs are NOT aligned with the dots and are not lines of best fit = [R] and 1/[R]

one graph is = ln[R] 

what order is it and how do you know

1st order

ln[R] —> line of best fit 

ln[R] = first order

y = mx + b

y= ln(k)

m = -Ea / R

x = 1/T

ln(a) = b

when drawing the arrows where do the arrows go

high e- density —> low e- density

acid reaction equation

HA (acid) + H₂O (base) ⇌ A⁻ (conjugate base) + H₃O⁺ (conjugate acid)

base reaction equation

B (base) + H₂O (acid) ⇌ BH⁺ (conjugate acid) + OH⁻ (conjugate base)

water autoionization equation

Kw = [OH-][H3O+]

what does both [OH-] & [H3O+] equal

1.0 × 10^-7

what does Kw =

1.0 × 10^-14

pH equation

pH = -log[H3O+]

[H3O+] equation

[H3O+] = 10^-pH

how to find pOH

pOH = 14 - pH

[OH-] = 10^pOH

if Ka / Kb > 1, what does this mean? strong or weak?

product favored (want)

strong because it completely dissociates into the particles in the products

if Ka / Kb < 1, what does this mean? strong or weak?

reactant favored (dont want,, majority is this)

weak because it partially dissociates

acid

donates H+

base

accepts H+

conjugate base

donates H+

goes with acid

conjugate acid

accepts H+

goes with base

exothermic

release heat into surroundings

• surroundings = increase temp

• inside = decrease temp

freezing, condensation, deposition

endothermic

absorb heat from surroundings

• surroundings = decrease temp

• inside = increase temp

melting, boiling, sublimation

AA + BB → AB

endo or exo

EXOthermic

weak → stronger bonds

AB → AA + BABY

endo or exo

ENDO thermic

strong → weak bonds

energetics on Ep

low Ep

entropics on configurations

high # of configs

negative H

postive S

product favored → -G

what you want !

postive H

negative S

reactant favored → + G

dont want !