Reaction Rates and Equilibria

Question 1

3 conditions required for a reaction to occur

Answer 1

1. collision
2. orientation: reactants must align properly to break and form bonds
3. energy: the collision must provide the energy of activation

Question 2

rate of the reaction equation

Answer 2

rate of reaction = change in concentration of reactant or product/ time

Question 3

factors that affect the rate of reaction

Answer 3

1. change in temperature
2. change in reaction conc
3. adding a catalyst

Question 4

what happens to the rate of reaction when increasing the temperature

Answer 4

there is an increase in the KE of the reactant molecules, which makes them move faster, makes them collide more often, and makes them collide with more energy

Question 5

what happens to the rate of reaction when increasing the reactant concentration

Answer 5

when there are more reacting molecules, more collisions that form products can occur and the reaction goes faster

Question 6

what happens to the rate of reaction when you add a catalyst?

Answer 6

speeds up the rate of the reaction of both the forward and reverse reactions by the same amountsk by providing an alternative pathway that has a lower activation energy. As a result, more collisions provide sufficient energy for reactants to form product

Question 7

activation energy

Answer 7

the minimum amount of energy required to break the bonds between atoms of the reactants

Question 8

what happens to k as you decrease activation energy?

Answer 8

the smaller the Ea the larger the k

Question 9

molecularity

Answer 9

the number of molecules that must collide to generate product

Question 10

half-life in a chemical reaction

Answer 10

the time required to halve the reactant concentration

Question 11

the half-life for a first-order reaction

Answer 11

t1/2 = ln2/k

Question 12

the half-life for a second-order reaction

Answer 12

t1/2 = 1/k[A]0

Question 13

dynamic equilibria

Answer 13

the reaction keeps happening both forward and reverse at the same rate

Question 14

equilibrium conditions

Answer 14

1. The rate of forward reaction is equal to the rate of the reverse reaction
2. the forward and reverse reactions continue at the same rate

Question 15

describe the properties of an equilibrium constant for a reversible chemical reaction

Answer 15

1. it is a fixed value at a specific temperature
2. the value that the system will evolve to reach an equilibrium

Question 16

what is activity

Answer 16

the effective molar conc of a species in the solution

Question 17

Kc

Answer 17

the numerical value obtained by substituting experimentally measured molar concentrations at equilibrium into the expression

Question 18

large Kc

Answer 18

large amounts of products produced from the forward reaction

Question 19

small Kc

Answer 19

low concentration of products and high concentration of reactants

Question 20

reaction quotient Q

Answer 20

uses non-equilibrium concentrations

Question 21

Q< Kc

Answer 21

more products will be synthesized

Question 22

Q> Kc

Answer 22

the reaction proceeds to the left

Question 23

le chatelier’s principle

Answer 23

when a stress is placed on a reaction at equilibrium the system responds by changing the rate of the forward or reverse reaction in the direction that relieves that stress

Question 24

k -1

Answer 24

the kinetic rate of the reverse reaction

Question 25

what is the relationship between the 2 rate constants of the forward and the reverse reaction?

Answer 25

k1/k-1 = Kc the rate is numerically identical to the equilibrium constant

Question 26

what is Ea (forward) - Ea (reverse) equal to

Answer 26

E (forward) - E (reverse)

Question 27

what state do catalysts decrease?

Answer 27

the transition state

Question 28

what does oxygen transport involve

Answer 28

an equilibrium between hemoglobin Hb, oxygen, and oxyhemoglobin HbO2

Question 29

Chatelier's principle of oxygen in water

Answer 29

oxygen is poorly soluble in water and so the equilibrium is in favour of the formatio of oxygen gas and not aqueous oxygen: the equilibrium shifts to the left O2 + H2O (equilibrium sign) O2

Question 30

how can we perturb the equilibrium of oxygen in water

Answer 30

by addition of hemoglobin which gives rise to oxyhemoglobin: the concentration of oxygen that is free decreases because it is bound to haemoglobin

Question 31

what happens when there is a high pressure of oxygen in the alveoli

Answer 31

the reaction shifts in the direction of oxyhemoglobin

Question 32

what happens when there is a low pressure of oxygen in the tissues

Answer 32

the equilibrium shifts to release oxygen from HbO2

Question 33

what happens at normal Patm

Answer 33

oxygen diffuses into the blood because the partial pressure of oxygen in the alveoli is higher than in the blood.

Question 34

what happens at a decrease in Patm

Answer 34

results in a lower pressure of oxygen which means less oxygen is available for the blood and body tissues

Question 35

the equilibrium constant for hemoglobin

Answer 35

Keq = [HbO2]/[Hb]p^4 O2 oxygen gas binds with a 1: 4 stoichiometry (1Hb: 4O2)

Question 36

what happens at an altitude of 18,000ft

Answer 36

a person will obtain 29% less oxygen and may result in hypoxia

Question 37

hypoxia

Answer 37

respiratory rate, headache, fatigue

Question 38

what happens when there is a general decrease of oxygen in the air

Answer 38

the equilibrium will shift in the direction of the reactants thus depleting the conc of HbO2

Question 39

thermodynamics

Answer 39

measure of energies

Question 40

state variables

Answer 40

define the conditions of a reaction in regard with pressure, volume, temperature and chemical composition

Question 41

system

Answer 41

the reaction mixture we have: where the reaction takes place

Question 42

1st law of thermodynamics

Answer 42

the change of the internal energy of a closed system equals to the heat supplies to the system minus the work done by the system

Question 43

internal energy U

Answer 43

a state function that represents all the internal energy present in our reactants, products and molecules

Question 44

variation of internal energy of a state

Answer 44

ΔU = q + w q= heat released/supplied by the system w= work done on/by the system

Question 45

how can work be manifested in chemistry

Answer 45

by observing a change in volume w = -pe ΔV pe = external pressure

Question 46

what is the variation of enthalpy at a constant pressure equal to?

Answer 46

the heat exchange ΔH = q

Question 47

enthalpy

Answer 47

comes from the combination of internal energy, pressure and volume and its variation is equal to heat.it is a state function and an extensive property

Question 48

extensive property

Answer 48

it depends on the state and size of the system

Question 49

what does the variation of enthalpy represent

Answer 49

the heat released or absorbed during a chemical reaction

Question 50

units of enthalpy

Answer 50

kJ/mol

Question 51

what does ΔHo mean

Answer 51

it is measured at the standard state (1atm, 298.15 K, and the solutions 1M)

Question 52

second law of thermodynamics

Answer 52

spontaneous processes are characterized by an increase in the disorder of the universe (entropy)

Question 53

what happens to the variation of entropy in spontaneous processes

Answer 53

the variation of entropy is equal or greater than the ratio between the heat exchange and teh temperature ΔS > q/t

Question 54

when is a reaction spontaneous

Answer 54

ΔH - TΔS < 0

Question 55

free energy

Answer 55

state function introduced by gibbs and it refers to the energy exchanged throughout a chemical reaction

Question 56

equation for gibbs free energy

Answer 56

ΔG = ΔH - TΔS

Question 57

ΔG < 0

Answer 57

exergonic and it occurs spontaneously

Question 58

ΔG > 0

Answer 58

endergonic and it requires an external input of energy to occur

Question 59

variation in the free energy in a chemical reaction

Answer 59

ΔG = ΔGo + RTlnQ

Question 60

free energy variation knowing the equilibrium constant

Answer 60

ΔGo = -RTlnK

Question 61

equilibrium constant is temperature-dependent

Answer 61

lnk = -ΔH/R (1/T) + ΔS/R

Question 62

what needs to be overcome to reach the products

Answer 62

the transition state