Topic 6: Rates and Extent of Chemical Changes

Question 1

Collision theory

Answer 1

Collisions between reacting particles with the sufficient activation energy are needed for chemical reactions

Question 2

The rate of reaction is dependent on…

Answer 2

1) The collision frequency of reacting particles - more collisions, the faster the reaction
2) The amount of energy reacting particles collide with - more reach activation energy, more successful collisions, the faster the reaction

Question 3

Factors affecting rates of reaction

Answer 3

1) Temperature
2) Concentration or Pressure
3) Surface Area
4) Use of Catalysts

Question 4

Concentration

Answer 4

More particles in the same volume of water makes collisions more frequent

Question 5

Pressure

Answer 5

Same number of particles in a smaller space makes collisions more frequent

Question 6

Surface Area

Answer 6

Smaller pieces increases surface area so, for the same volume, particles have more area to work on making collisions more frequent

Question 7

Activation energy

Answer 7

The minimum amount of energy that reacting particles must have in order for a reaction to occur

Question 8

Catalysts

Answer 8

Substances that can increase the rate of reaction by lowering the activation energy and thereby increasing the likelihood of successful collisions without being in the reaction

Question 9

TWO RATES PRACTICAL

Answer 9

-

Question 10

(Dynamic) Equilibrium

Answer 10

When the forward and backward reactions happen at the same rate meaning there is no overall effect as the concentrations of product and reactant do not change

Question 11

Closed system

Answer 11

A system in which reactants and products can neither be added nor removed

Question 12

Le Chatelier’s Principle

Answer 12

If any of the conditions of a reversible reaction at equilibrium are changed, the system will counteract this change

Question 13

If the position of equilibrium lies to the right…

Answer 13

The concentration of products is greater than the reactants

Question 14

If the position of equilibrium lies to the left…

Answer 14

The concentration of reactants is greater than the products

Question 15

Changes to a reversible reaction

Answer 15

1) Temperature
2) Concentration
3) Pressure

Question 16

If the reaction in one direction is exothermic

Answer 16

The reaction in the other is endothermic

Question 17

Rate of reaction

Answer 17

Amount of reactant used | Amount of product formed
÷
Time

Question 18

Conversion of area

Answer 18

mm^2 –> cm^2 = ÷10^2
cm^2 –> m^2 = ÷100^2
m^2 –> km^2 = ÷1000^2

Question 19

Conversion of volume

Answer 19

mm^3 –> cm^3 = ÷10^3
cm^3 –> dm^3 = ÷10^3
cm^3 –> m^3 = ÷100^3
m^3 –> km^3 = ÷1000^3

Question 20

Temperature

Answer 20

Higher temperature means particles have more energy and move faster therefore they collide more frequently and more have the required activation energy

Question 21

Decreasing temperature in a reversible reaction (3)

Answer 21

1) Decrease temperature –> equilibrium shifts in exothermic direction
2) Shift in exothermic direction –> produces more heat
3) More products of exothermic reaction created | less products of endothermic reaction

Question 22

N-2 + 3H-2 –> 2NH-3

Answer 22

4 moles on left | 2 moles on right

Question 23

Increasing pressure in a reversible reaction (2)

N-2 + 3H-2 –> 2NH-3

Answer 23

1) Increasing pressure –> equilibrium shifts to reduce it
2) Equilibrium shift –> equilibrium shift in the direction producing fewer molecules
(More 2NH-3 produced as fewer moles on the right)

Question 24

Changing concentration in a reversible reaction (reactant + product)

Answer 24

1) Increase concentration of reactants –> equilibrium shifts right –> more products formed –> decrease concentration of reactants
2) Increase concentration of products –> equilibrium shifts left –> more reactants formed –> decrease in concentration of products