Chapter 10 Reaction Rates And Equilibrium

Question 1

rate of reaction

Answer 1

The change in concentration of a reactant or a product in a given time.
Rate= change in conc. (mol dm-3) / time (s)

Question 2

Factors that can change rate of reaction

Answer 2

concentration- increase in conc. increases no. of particles in the same volume. They are closer together and collide more frequently
temperature
use of a catalyst
surface area of solid reactants
Pressure (gas)-conc. of gas molecule increases

Question 3

collision theory

Answer 3

Two reacting particles must collide for a reaction to occur, and must be in the correct orientation and have sufficient energy to overcome the activation energy of the reaction.

Question 4

How can the progress of a reaction be followed?

Answer 4

• monitoring the removal (decrease in conc.) of reactant
• following the formation (increase in conc.) of a product
  Gas
• monitoring the volume of gas produced at regular time intervals using gas collection
• monitoring the loss of mass of reactants using a balance

Question 5

initial rate of reaction

Answer 5

The change in concentration of a reactant or product per unit time at the start of the reaction: t = 0

Question 6

catalyst

Answer 6

A substance that increases the rate of a chemical reaction without being used up in the
process; a catalyst provide an alternative route for the reaction with lower activation energy.

Question 7

intermediate

Answer 7

A species formed during a reaction that reacts further and is not present in the final products.

Question 8

homogeneous catalysis

Answer 8

A reaction in which the catalyst and reactants are in the same physical state, which is most frequently the aqueous or gaseous state.

Question 9

heterogeneous catalysis

Answer 9

A reaction in which the catalyst has a different physical state from the reactants; frequently reactants are gases whilst the catalyst is a solid.

Question 10

adsorbed

Answer 10

reactants are weakly bonded onto the surface of the catalyst, where the reaction takes place

Question 11

desorption

Answer 11

Release of an adsorbed substance from a surface.

Question 12

Features of a Boltzman distribution

Answer 12

• no molecules have 0 energy, the curve starts at the origin
• Area under curve = total no. of molecules
  -no max energy, curve doesn’t meet x axis
  x-axis: energy y axis:number of molecules with a given energy

Question 13

reversible reaction

Answer 13

A reaction that takes place in both forward and reverse directions.

Question 14

dynamic equilibrium

Answer 14

The equilibrium that exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and concentrations do not change.

Question 15

closed system

Answer 15

A system isolated from its surroundings

Question 16

position of equilibrium

Answer 16

The relative quantities of reactants and products, indicating the extent of a reversible reaction at equilibrium

Question 17

Le Chatelier’s principle

Answer 17

When a system in dynamic equilibrium is subjected to a external change, the system readjusts itself to minimise the effect of the change and to restore equilibrium.

Question 18

equilibrium constant Kc

Answer 18

A measure of the position of equilibrium; the magnitude of an equilibrium constant indicates whether there are more reactants or more products in an equilibrium system.
Kc=1 equilibrium halfway between reactants and products
Kc1 equilibrium towards the products