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chemistry > unit 9 - kinetics & equilibrium > Flashcards

unit 9 - kinetics & equilibrium Flashcards

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1
Q

a chemical equation describes

A

a chemical change (reaction)

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2
Q

kinetics

A

deals with the rates of chemical reactions

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3
Q

rate

A

describe how fast a reaction takes place

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4
Q

high rate

A

= fast (less time)

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5
Q

low rate

A

= slow (more time)

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6
Q

collision theory

A

For reactions to occur reactant particles must collide.

1) Spatial Orientation must be exact

2) Activation Energy must be met

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7
Q

more effective collisions: temperature

A

Increase in temperature increases reaction rates, due to more KE.

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8
Q

more effective collisions: concentration

A

The greater the concentration (M) of reactants, the greater the reaction rates.

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9
Q

more effective collisions: nature of the reactants

A

Ionic substances react faster (dissociate) than covalent ones
(larger & contain more bonds).

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10
Q

more effective collisions: surface area

A

Increase in surface area, increases the reaction rate because more
surfaces are exposed.
**powder

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11
Q

more effective collisions: pressure

A

Increase in pressure on gases
increases reaction rates, because it
increases the concentration of the
particles.

**Little or no effect on solids & liquids

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12
Q

more effective collisions: catalyst present

A

Increase the reaction rate by providing lowering the activation
energy & creates an alternate pathway.

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13
Q

potential energy

A

is the energy stored within the bonds of reactants and products of a reaction.

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14
Q

Heat Content (Heat of Reaction)

A

amount of heat absorbed or released in a chemical reaction

Heat of Reaction (ΔH = PEproducts – PEreactants)

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15
Q

PED - Endothermic Reactions

A
  • Gain more energy than is released
  • Energy of the products is higher
    than the reactants
  • Energy is absorbed

● ΔH is + (positive)

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16
Q

PED - Exothermic Reactions

A
  • More energy is lost to the surroundings
  • Products have less energy than
    the reactants
  • Energy was released
  • ΔH is - (negative)
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17
Q

∆H is the…

A

difference between the energy
needed to break the bonds in the reactants, and the energy given out when new bonds are formed in the products

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18
Q

ΔH is positive when the reaction is endothermic.

A

Heat of products are greater than reactants

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19
Q

ΔH is negative when the reaction is exothermic.

A

Heat of reactants are greater than the products

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20
Q

Endothermic: heat is a…

A

reactant (on left side)

Ex. N2 + O2 + 182.6 KJ → 2NO

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21
Q

Exothermic: heat is a…

A

product (on right side)

Ex. 2H2 +O2 → 2H2O + 486 KJ

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22
Q

(Δ H) is defined as the

A

difference in PE of the Products and the PE of the reactants

aka heat of reaction

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23
Q

Δ H is proportional To the AMOUNT of Material undergoing reaction.

A
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24
Q

Heat of Reaction & Surrounding Temperature: Exo Rxn

A

-Release Energy so the surrounding temperature (outside the reaction) gets warmed.

Ex. Heat Pack
Ex. From Table I the dissolving of NaOH (s), LiBr (s)

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25
Q

Heat of Reaction & Surrounding Temperature: Endo Rxn

A

-Absorb Energy so the surrounding temperature (outside the reaction) gets colder

Ex. A Cold Pack
Ex: From Table I the dissolving of KNO3, NH3Cl, NH4NO3

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26
Q

Surface Temp: Exothermic

A

Reactions in which Heat is Released to the surroundings

  • Contents of test tube get Hotter

-Surrounding Temperature INCREASES

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27
Q

Surface Temp: Endothermic

A

Reactions where Heat is Absorbed from the surroundings

  • Contents of test tube get Colder
  • Surrounding Temperature DECREASES
28
Q

equilibrium

A

is the state of balance between 2 opposite reactions occuring at the same time
- most reactions are reversible -><- must take place in a closed system

29
Q

the state of equilibrium is…

A

dynamic = changing

30
Q

equilibrium is reached when the reaction rates:

A

(Forward →) & (← Reverse) ARE EQUAL (are the same)

31
Q

AT EQUILIBRIUM, concentration of reactants

A

≠ concentration of products

  • concentration of reactants and products are CONSTANT (staying the same)
32
Q

point of equilibrium (balance) is affected by:

A
  • Temperature Change (Δ T)
  • Change in [ ] Concentration
  • Change in Pressure (on gases)
33
Q

reaction non-reversible

A

goes to completion

34
Q

A Reaction is NON - REVERSABLE when:

A
  1. a product is removed
  2. a product is a gas & the gas escapes
    ex: NaHCO3 + HCl → NaCl + H2O + CO2 (g)
  3. a product is a precipitate (insoluble) and can not react again **double replacement, table F
  4. a product is H2O
35
Q

types of physical equilibrium: phase equilibrium

A

Ex. H2O (s) → H2O (l) If no Δ T
←
- At 0°C in a closed container, both water and ice exist at the same time.

** remember: melting point = freezing point
Ex. H2O (l) → H2O (g) If no Δ T
←
- At 100°C in a closed container, both liquid and gas exist at the same time.

36
Q

phase equilibrium: in the open container

A

liquid evaporates until it is completely evaporated
H2O (l) -> H2O (g)

37
Q

in the closed container

A

evaporation continues but it is balanced by condensation

H2O ( l ) → H2O (g)
←

38
Q

types of physical equilibrium: solution equilibrium

A

dissolving
NaCl (s) → NaCl (aq)
←
recrystallization

  • rate dissolving = rate recrystall.
  • solution is saturated
39
Q

Solubility

A

Mass of solute (solid) which can
dissolve in a given amount of solvent.

40
Q

equilibrium is reached when the

A

concentration of the reactants and products remain constant

  • the rate of the forward reaction equals the rate of the reverse reaction so there is no net change in the system
41
Q

Le Chatelier’s Principle

A

if a chemical system at equilibrium is disturbed it will change (SHIFT) in the direction to relieve the stress

  • the result is a new equilibrium at a diff point
42
Q

how is stress applied

A
  • change of concentration of reactants or products
  • change of temperature
  • change of pressure
43
Q

equilibrium: increase in concentration

A
  • if concentration of a substance increases, the reaction that reduces the substance is favored
44
Q

equilibrium: increase in temperature

A
  • temperature increase will shift a system in equilibrium to favor the endothermic reaction (to use up heat)
45
Q

equilibrium: decrease in concentration

A

if concentration of a substance decreases, the reaction that increases that substance is favored

46
Q

equilibrium: decrease in temperature

A

temperature decrease will shift a system in equilibrium to favor the exothermic reaction (replace the heat lost)

47
Q

le chatelier’s principle: PRESSURE

A
  • pressure only effects the equilibrium of a system in which GASES are involved
  • pressure does not effect the equilibrium when there is no change in moles of gas
48
Q

equilibrium: increase in pressure

A

an increase in pressure will favor the direction with fewer moles of gas

49
Q

equilibrium: decrease in pressure

A

a decrease in pressure favors the direction with more moles of gas

50
Q

le chatelier’s principle: catalysts

A
  • catalyst increase the rate of both the forward and reverse reactions equally
  • equilibrium is not disrupted and the concentration of reactants and products stay constant
51
Q

common ion effect

A

ex: NaOH (s) ⟷ Na+ (aq) + OH- (aq) + 10.6 kcal

  • add KOH (adds OH-), amt NaOH (s) increases, Na+ decreases
52
Q

entropy

A

a degree of randomness or disorder

53
Q

More Organized → More Disorder

A

Solid to Liquid State
Solid to Gas State
Liquid to Gas State
NI3 (g) → N2 (g) + 3 I2 (g)
NaCl (s) → NaCl (aq)

54
Q

Spontaneous Reactions:

A

A reaction that when initiated will continue without any outside influence.

54
Q

Spontaneous Reactions are more favorable when:

A

1) Reactions are Exothermic- lower activation energy & Loss of energy (more stable state)

2) Increase in Entropy- Increase in Disorder

55
Q

In nature systems usually move in the

A

exothermic and more disorder direction

56
Q

what does nature prefer

A
  • analogy: bedroom
  • low energy and high entropy
57
Q

Law of Mass Action:

A

When a reversible reaction reaches equilibrium there is a mathematical relationship between the reactants and products.

58
Q

what can Law Of Mass Action help predict

A

This can help us predict if the product or reactant concentrations would be greater at equilibrium or if they will be equal.

59
Q

what is included in Keq equations

A

**Only concentration of gases and ions are included in the expression, OMIT solids & liquids.

60
Q

what is Keq used to predict

A

Keq value is used to predict the concentration of products and
reactants at equilibrium

61
Q

Keq greater than 1

A

→ there are more products than
reactants at equilibrium

62
Q

Keq less than 1

A

there are more reactants than products
at equilibrium

63
Q

Keq = 1

A

[Products] = [ Reactants] at equilibrium

64
Q

when there is a decrease in volume, the equilibrium will shift to favor the

A

direction that produces fewer moles of gas

65
Q

when there is an increase in volume, the equilibrium will shift to favor the

A

direction that produces more moles of gas

chemistry (11 decks)

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