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Chem 112 > Exam Review > Flashcards

Exam Review Flashcards

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1
Q

delta H and spontaneity

A

H +ve- endothermic and non-spontaneous

H-ve - exothermic and spontaneous

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2
Q

Gibbs energy

A

free energy of a reaction, indicates spontaneity
-ve delta G mean spontaneous(favours products)
+ve delta G means non spontaneous(favours reactants)

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3
Q

entropy (S)

A

thermodynamic property related to energy configurations
- greater entropy means greater number of configurations(increase in disorder)
positive entropy means spontaneous
negative entropy means non-spontaneous

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4
Q

3rd law of thermodynamics

A

the entropy of a pure perfect crystal at 0K is 0

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5
Q

2nd law of thermodynamics

A

all spontaneous processes produce an increase in the entropy of the universe

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6
Q

physical vs chemical equilibrium

A

physical equilibrium: equilibrium of a substance from one phase to another
chemical equilibrium: equilibrium of 2 substances(reactants and products)

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7
Q

at equilibrium concentrations become _____________ and rates become _____________

A

constant, equal

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8
Q

Large K means _______

Small K means _______

A
  • reaction strongly tends to go to completion(alot of products)
  • reaction strongly does not tend to go to occur (alot of reactants)
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9
Q

Which way will the rxn shift when:
QK
Q=K

A
  • to the right
  • to the left
  • at equilibrium, no change
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10
Q

Le Chatelier’s Principle

A

a equilibrium is a dynamic system that can respond to change

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11
Q

Which way does the rxn shift
- increasing conc of starting materials
increasing conc of products

A
  • shifts towards products

- shifts towards reactants

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12
Q

Pressure and volume effect

  • reducing volume(increasing pressure)
  • increasing volume (reducing pressure)
A
  • shifts towards direction with fewer mols of gas

- shifts towards direction that produces more moles of gas

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13
Q

Temperature effect on equilibrium

  • increasing temperature
  • decreasing temperature
A
  • shifts towards direction of endothermic reaction

- shifts towards direction of exothermic reaction

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14
Q

Arrhenius theory of acids and bases

A

when dissolved in water, acids produce H+ ions

when dissolved in water, bases produce OH- ions

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15
Q

Bronsted-Lowry Theory of acids and bases

A
  • acids are proton donors and protonate water
  • bases are proton acceptors and deprotonate water
  • conjugate acid base pairs differ by one H+
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16
Q

Lewis theory of acids and bases

A
  • a lewis acid is an electron pair acceptor(electrophile)

- a lewis base is an electron pair donor(nucleophile)

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17
Q

amount of ionization of an acids depends on (2)

A
  1. initial concentration of the acid

2. the value of the ionization constant (Ka)

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18
Q

3 rules to predict acids/bases

A
  1. metal ions with a 1+ or 2+ charge do not affect pH(metal ions with a >+2 charge can act as an acid
  2. polyatomic cations in water often act as acids
  3. many anions in water will act as a base
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19
Q

What determines acid strength

A
  1. electronegativity of neighbouring atoms

2. stability of the conjugate base(delocalization/resonance)

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20
Q

What determines base strength

A
  1. electronegativity of neighbouring atoms
  2. stability of the conjugate acid
  3. substituent groups on N
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21
Q

Common ion effect

A
  • ionization of a weak acid is suppressed by its conjugate base or a strong acid
  • ionization of a weak base is suppressed by its conjugate acid or a strong base
22
Q

Buffer solutions

A

have the ability to neutralize a small amount of strong acid or strong base

23
Q

saturated solution

A

no more solute can dissolve at a given temperature

24
Q

unsaturated solution

A

the solute can fully dissolve in a solution and more solute can dissolve

25
Q

supersaturated solution

A

has an excess of solute(higher than saturation point)

solution is unstable and will begin to precipitate

26
Q

common ion effect in solubility

A

the solubility of a slightly soluble ionic compound is lowered in the presence of a common ion

27
Q

Limitations of the Ksp concept

A
  1. limited to slightly soluble salts
  2. uncommon ion effect(uncommon ions increase solubility)
  3. Ksp assumes complete dissociation
28
Q

Predicting precipitation
Q>K
Q=K
Q

A
  • Precipitation should occur”supersaturated”
  • solution is saturated
  • precipitation cannot occur “unsaturated”
29
Q

redox reactions

A

a reaction consisting of oxidation and reduction half reactions
- oxidation is loss, reduction is gain

30
Q

Balancing redox reactions

A
  1. write half reactions and balance those
  2. balance O atoms using H20
  3. balance H atoms using H+
  4. balance charge with electrons
  5. balance # of electrons
31
Q

electrochemical cells vs electrolytic cells

A

electrochemical cells- if the reaction is spontaneous, electricity will be generated
electrolytic cells- if the reaction is non-spontaneous, it can be forced to happen with an external source

32
Q

electrochemical cell conventions

A

oxidation occurs at the anode

reduction occurs at the cathode

33
Q

standard cell potential

A

voltage due to a spontaneous redox reaction that forces electrons into motion

34
Q

standard reduction potential

A

the potential at each half cell

35
Q

cell potentials and spontaneity
Ecell>0
Ecell=0
Ecell<0

A
  • reaction proceeds spontaneously as written
  • reaction is at equilibrium
  • reaction proceeds in the reverse direction spontaneously
36
Q 
Batteries
Primary cells:
Secondary cells:
Reserve batteries:
Flow batteries and fuel cells:
A
  • non reversible, non rechargeable
  • can be reversed, rechargeable
  • designed for long term storage or delivering high power over a short time
  • can be run indefinitely
37
Q

reactions occur at _________

A

functional groups

38
Q

Nucleophiles and Electrophiles

A
  • can cause bonds to form and break

nucleophiles transfer electrons to electrophiles

39
Q

steps to analyzing a reaction mechanism

A
  1. Housekeeping
    - redraw starting materials, number relevant atoms
  2. Find reactivity
    - determines bonds formed and broken
    identify the nucleophile and electrophile
  3. Draw mechanisms/ draw the product
    - draw curved arrows/ interpret curved arrows
    - check that formal charges, atoms, and total charge are conserved
40
Q

types of reactions:

Acid-Base Proton Exchange

A
  • a proton is exchanged in a reversible reaction

- nucleophile (e donor) acts as a base

41
Q

nucleophile addition to a carbon double bonded to an oxygen

A

double bond is broken, Nu single bonds to carbon, oxygen is now single bonded not double bonded

42
Q

Reactivity can be influenced by

5

A
  1. Electronegativity
  2. Induction
  3. Atom size
  4. Electron delocalization
  5. Steric hindrance
43
Q

Role of electronegativity on electrophilicity

A
  • electronegative elements pull electron density towards them so greater electronegativity makes better electrophiles
44
Q

role of induction on electrophilicity

A

greater electronegativity of R group, greater electrophilicity

45
Q

role of atom size on electrophilicty

A

larger atoms are able to disperse negative charge over a larger area so they are a worse electrophile and a better nucleophile

46
Q

role of electron delocalization on electrophilicity

A

electron delocalization creates multiple sites of reactivity(resonance structures) so it stabilizes the molecule
- increasing electron delocalization(having more resonance structures) increases electrophilicity

47
Q

role of steric hindrance on electrophilicity

A

greater bulkiness of R group means more hindrance and less electrophilicity

48
Q

What factors control reaction rate (3)

A
  1. Concentration: greater conc, more molecules to collide
  2. temperature: increased temperature, more molecules at a higher kinetic energy
  3. Molecular structure: molecules must collide at their reactive sites
49
Q

rate constant

A
  • proportionality constant that relates concentrations and orders to the observed rate
  • larger k value means faster reaction
  • overall reaction order determines units for k
50
Q

overall reaction order of 0

A
  • sum of exponents=0
  • rate is constant throughout rxn
  • units of k same as unit for rate M/s
51
Q

overall first order reaction

A
  • sum of exponents equals 1
  • rate changes throughout rxn as concentration changes
  • units of k is 1/s
52
Q

overall second order reaction

A
  • sum of exponents equals 2
  • rate changes throughout rxn as concentration changes
  • unit of k must be 1/MS

Chem 112 (1 decks)

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