Rates of reaction - Chapter 4

Question 1

Rates of reactions definition

Answer 1

Change in concentration of any one reactant or product per unit time

Question 2

Concentration definition

Answer 2

Number of particles per unit volume

Question 3

Rate of reactions formula

Answer 3

Change in concentration of any one reactant or product / time taken

Question 4

Law of conservation of energy definition

Answer 4

Energy can be converted from one form to another but the total energy in the universe is constant

Question 5

Activation energy definition

Answer 5

Minimum energy required for colliding particles to have a successful collision. Symbol (Ea) Unit (Joules)

Question 6

Factors that affect rate of reaction

Answer 6

1. Concentration (greater)
2. Particle size/surface area (smaller)
3. Temperature (greater)
4. Pressure (greater)
5. Catalyst
6. Solvent (greater)

Question 6

For a reaction to happen particles must

Answer 6

1. Collide
2. Collide with correct orientation
3. Must collide with minimum energy

Question 7

Catalyst definition

Answer 7

Substance that alters the rate of a chemical reaction but not consumed in the reaction

Question 8

5 types of catalysis

Answer 8

1. Homogeneous
2. Heterogeneous
3. Autocatalysis
4. Negative catalyst (inhibitor)
5. Catalytic poison

Question 8

Experiment to show the rate of reaction

Answer 8

Monitoring rate of production of oxygen from hydrogen peroxide using manganese dioxide as a catalyst

Question 9

What is a homogeneous catalyst and an example

Answer 9

Both the reactants and the catalyst in the same phase

Iodine snake experiment
H202 —- H20 + 1/2 02

Question 10

What is a heterogeneous catalyst and an example

Answer 10

Different phases than reactants
N2 + 3H2 —- 2NH3
Catalyzed by Fe

Question 11

What is an autocatalysis

Answer 11

Reactant or product is also a catalyst

Question 12

What is a negative catalyst and an example

Answer 12

Slows down a reaction
Lead tetraethyl prevents pre-ignition of petrol

Question 13

What is a catalytic poison and an example

Answer 13

Destroys effects of catalysts
Arsenic kills people as it poisons enzymes in the body

Question 14

Mechanisms/theories of catalysis

Answer 14

1. Surface adsorption theory
2. Unstable intermediate theory
3. Intermediate formation theory

Question 15

What is surface adsorption theory and an example

Answer 15

Example is the heterogeneous catalysis of the addition of hydrogen to ethene to produce ethane
C2H4 + H2 —- C2H6

Question 16

What is adsorption

Answer 16

Attracts onto the surface, the gases contract and increases rate of reactions

Processes-
Adsorption – Reaction – Desorption

Question 17

What is the unstable intermediate theory

Answer 17

One of the reactants combines with the catalyst and forms an unstable intermediate. Reaction then proceed with the lower activation energy

Question 18

What is a catalytic converter

Answer 18

Device in the exhaust system or a motor which contains catalysts to convert pollutants in the exhaust gases to less harmful substances

Question 19

Use for a Maxwell Boltzmann curve

Answer 19

Shows distribution of different energies across the particles in a system

Question 19

What is intermediate formation theory and an experiment to prove it

Answer 19

Catalysis acts by providing a new path with lower activation energy

Potassium sodium tartrate and hydrogen peroxide experiment