Reaction Rates And Equilibrium

Question 1

What is the collision theory

Answer 1

For a reaction to occur, particles must collide in the correct orientation and with sufficient kinetic energy to overcome the activation energy

Question 2

What is activation energy

Answer 2

The minimum energy which particles need to collide to starch a reaction

Question 3

What is rate of reaction

Answer 3

The rate of reaction measures how fast a reactant is being used up or how fast a product is being formed

Question 4

Rate =

Answer 4

Change in conc/ time

Y/x on graph

Question 5

Rate units

Answer 5

Moldm-3 s-1

Question 6

Factors that affect rate

Answer 6

Conc or pressure
Temperature
Surface area
Catalyst

Question 7

How does temerature affect reaction rate

Answer 7

HIGHER temp= more particles with higher kinetic energy

More successful collisions per second

Question 8

Surface area- how does it affect reaction rate

Answer 8

Increased surface area = total number of collisions increased

Greater probability of successful collisions per second

Greater SA:v ratio = more contact

Question 9

How do pressure /conc affect reaction rate

Answer 9

More particles per unit volume - frequency of collisions increased

Greater number of successful collisions per second

Question 10

METHODS for following reaction progress

Answer 10

Monitoring change in masss - moss of mass of reactants using a balance( when product is a gas)

Volume of gas given off

Question 11

What is a catalyst

Answer 11

Increases the rate of reaction by providing an alternate reaction pathway with a Lower Ea

Chemically unchanged

Question 12

TYPES of catalyst

Answer 12

Homogenous

Heterogenous

Question 13

Homogenous catalyst

Answer 13

Same psychical state as the reactants
E.g. In an aqueous state - or a reaction between 2 aqueous solutions e.g. Enzyme

• forms an intermediate species- the reactants combine with the catalyst to make an intermediate speciies which then reacts to form the products and reform the catalyst

Question 14

Heterogenous catalyst

Answer 14

Different phase from the reactant

• e.g. The haber proccess - gases passed over a solid iron catalyst

Reaction happens on the surface of the catalyst , so increasing the SA of the catalyst increases the rate of reaction

E.g. Usually solids wheras reactants are gaseous/solutions

ADSORBED9 weakly bonded, to surface and removed by DESORPTION

Question 15

WHAT DOES the Boltzmann distribution show

Answer 15

Starts at o,o because there are no molecules that have 0 energy

Most moecluels are original t moderate speed

Some molecules move sat and have high energy

Curve NEVER meets the x aci because there’s no maximum energy for a molecule

Question 16

Boltzmann distribution - area under the curve

Answer 16

Number of moecluels

Question 17

Temperature- the Boltzmann dis bitcoin

Answer 17

Peak moves , greater proportion exceed Ea

Question 18

Catalyst - Boltzmann distribution

Answer 18

Ea reduced

Question 19

Reversible

Answer 19

Reactions that take place in both the forward and backward directions

Question 20

Industry and environmental stability - benefits of using catalysts

Answer 20

Iron is used as a catalyst in ammonia production- means temperature design have to be so high( expensibe)

Lower temps+ pressures used- energy saved- less co2 and fossil fuels

Question 21

Dynamic equilibrium

Answer 21

Forward and backward reaction are occurring at equal rates

The concentration o reactants and products remain CONSTANT

Can only happen in a closed system - no external conditions, isolated from surroundings

Question 22

As reactants get used up…

Answer 22

Forward reaction slows

As more product is formed - the reverse reaction speeds up

After a while - forward reaction wil be going at same rate as backwards = amounts o products and reactants won’t change

Question 23

Le chateleirs principle

Answer 23

If an external condition is changed, the equilibrium will shift to oppose the change

Question 24

If equilibrium moves left…

Answer 24

Get more reactants

SMALLER yield

Question 25

If equilibrium moves right…

Answer 25

Get more products

GREATER yield

Question 26

Factors affecting equilibrium

Answer 26

Temperature
Concentration
Pressure

Question 27

How does temperature affect equilibrium

Answer 27

As temp decreases, the equilibirum will shift in the exothermic direction to product more heat

If temp increases , équilibré will shift in the endothermic direction, to abosrb more heat

Question 28

How does concentration effect dynamic eulilibium

Answer 28

If you increase reactant concentration, equilibrium shifts right o make more products

If you increase product concentration, equilibrium shifts left to make more reactants

• decrease reactant = shift left to make more reactants

Question 29

How does pressure affect equilibrium

Answer 29

Gases only
- INREASING pressure shifts equilibirum to side with fewer gas moles to reduce pressure

• decreasing pressure shifts equilibrium to side with more gas molecules to raise pressure

Question 30

Catalyst - dynamic equilibrium

Answer 30

QwNO EFFECT on equilibirum position

Speed up the forward and reverse reactions by the same amount

Equilibirum is reache faster