Chp 4 Rates of Chemical Reactions

Question 1

Rate of reaction

Answer 1

The change in concentration of any one reactant or product per unit time

Question 2

Collision theory

Answer 2

1. Collide
2. With correct reaction geometry
3. Have the activation energy

Question 3

Activation energy (Eᴀ)

Answer 3

The minimum energy colliding particles require to have a successful collision hence successful reaction

Question 4

Breaking bonds

Answer 4

Require energy

Question 5

Forming bonds

Answer 5

Releases energy

Question 6

Exothermic reaction

Answer 6

Energy is released in the form of light and heat

Question 7

Endothermic reaction

Answer 7

Reactants absorbs heat energy from surroundings to form products

Question 8

Allotropes

Answer 8

Different physical forms of the same elements

Question 9

Factors affecting rate of reaction:
Catalyst

Answer 9

A substance which changes the rate of a reaction without being consumed in the reaction,
Provides an alternate reaction pathway that has a lower activation energy.

Question 10

Homogeneous catalysis

Answer 10

A homogeneous catalyst is in the same phase as the reactants. (Physical State)
E.g. Iodine snake
Hydrogen preoxide –> water and oxygen
Addition of aqueous iodide ion as catalyst

Question 11

Spectator ions

Answer 11

Ions which do not take part in a reaction

Question 12

Heterogeneous catalysis

Answer 12

A heterogeneous catalyst is in a different phase than the reactants

Reduction of Ethene
C₂H₄ + H₂ -> C₂H₆
Catalysed by Ni

Question 13

Autocatalysis

Answer 13

One of the products of the reaction acts as a catalyst for the reaction
Potassium permanganate and ethanedioic acid forms Magnesium which acts as a catalyst

Question 14

Negative catalyst (inhibitor)

Answer 14

Slows down a reaction

Question 15

Catalytic poison

Answer 15

Destroys the effect of a catalyst
Lead poisons the catalyst in a catalytic converter

Question 16

Adsorption

Answer 16

Reactants diffuses onto surface of catalyst. bonds weakened when adsorbed
Concentration weaken as reactants are clumped together

Question 17

Absorption

Answer 17

Contact throughout an object

Question 18

Enzyme

Answer 18

Biological catalyst

Question 19

Catalytic converter

Answer 19

A device in car exhaust, containing a catalyst to convert pollutant gas into less harmful ones

Question 20

Dust explosion

Answer 20

If a massive surface area of dust is ignited, a huge sudden release of energy can occur.
If happens in a confined space a dust explosion will occur.

Question 21

Instantaneous rate of reaction

Answer 21

Rate of reaction at a certain time
Found using line of best fit in graph

Question 22

Factors affecting rate of reaction:
Nature of reactants
(Covalent substance)

Answer 22

Reacts slower - Bonds have to be broken

Question 23

Factors affecting rate of reaction:
Nature of reactants
(Ionic substance)

Answer 23

Reacts faster - Ionic solution in aqueous solution are already dissolved in water

Question 24

Factors affecting rate of reaction:
Particle size

Answer 24

Larger surface area for collisions

Question 25

Factors affecting rate of reaction:
Concentration

Answer 25

More collisions between reactant particles

Question 26

Factors affecting rate of reaction:
Temperature

Answer 26

Higher temperature, greater rate of reaction
Increase activation energy of particles so effective collision can occur

Question 27

Factors affecting rate of reaction:
Presence of solvent

Answer 27

Particles in solution are freer to move around and collide with each other

Question 28

Factors affecting rate of reaction:
Pressure

Answer 28

Only occurs in gas
Increase in pressure = increase concentration of gas

Question 29

The surface adsorption theory

Answer 29

Adsorption -> Reaction -> Desorption
Generally heterogenous catalysis

Question 30

The unstable intermediate theory

Answer 30

One of the reactants combines with the catalyst and forms an unstable intermediate
Generally homogeneous catalysis

Question 31

Examples of catalytic converter

Answer 31

Ceramic honeycomb coated with platinum, palladium and rhodium catalysts
Carbon monoxide -> Carbon dioxide
Nitrogen monoxide -> Nitrogen
Hydrocarbons -> Carbon dioxide and water