rate & extent of chemical change

Question 1

what is collision theory?

Answer 1

the theory that chemical reactions can only occur when reacting particles collide with each other with sufficient energy

Question 2

what is activation energy?

Answer 2

minimum amount of energy that particles must have to react

Question 3

describe the effect of increasing temperature on rate of reaction

Answer 3

• particles have more energy
• more collisions have energy higher than activation energy
• higher frequency of collisions

Question 4

describe the effect of increasing concentration on rate of reaction

Answer 4

• more particles in the same volume
• particles closer together
• higher frequency of collisions

Question 5

describe the effect of increasing pressure on rate of reaction

Answer 5

• particles closer together
• higher frequency of collisions

Question 6

describe the effect of increasing surface area on rate of reaction

Answer 6

• more surface available for collisions
• higher frequency of collisions

Question 7

how do catalysts work?

Answer 7

increase rate of reaction without being used up, by providing an alternative reaction pathway with a lower activation energy

Question 8

why are catalysts are used in industry?

Answer 8

• reduces temperature required for a reaction - lowers energy costs
• catalysts can be reused
• reactions are quicker

Question 9

define a reversible reaction

Answer 9

where products of reaction can react to produce original reactants

Question 10

how can the direction of a reversible reaction be changed?

Answer 10

by changing the conditions of the reaction

Question 11

if a reversible reaction is exothermic in one direction, what kind of reaction will it be in the other direction?

Answer 11

endothermic in the opposite direction, and the same amount of energy is transferred in each case

Question 12

when is equilibrium achieved?

Answer 12

when a reversible reaction occurs in apparatus which prevents escape of reactants and products and the forwards and reverse reactions occur at exactly the same rate

Question 13

what do the relative amounts of all reactants and products at equilibrium depend on?

Answer 13

the conditions of the reaction

Question 14

what is Le Chatelier’s Principle used for?

Answer 14

used to make predictions about reactions at equilibrium

Question 15

What is Le Chatelier’s principle?

Answer 15

if a system at equilibrium and a change is made to any conditions, the system will respond to counteract the change

Question 16

what are the factors affecting a reaction at equilibrium?

Answer 16

• concentration of reactants or products
• pressure - if reaction involves gases
• temperature
• catalysts

Question 17

if concentration of a reactant is increased, what will happen to equilibrium?

Answer 17

more products will be formed until equilibrium is reached again (forward reaction favoured)

Question 18

if concentration of a product is increased, what will happen to equilibrium?

Answer 18

less products will be formed until equilibrium is reached again (reverse reaction favoured)

Question 19

in an equilibrium reaction, an increase in pressure causes the equilibrium position to shift towards which side?

Answer 19

the side with the smaller number of molecules

Question 20

in an equilibrium reaction, a decrease in pressure causes the equilibrium position to shift towards which side?

Answer 20

the side with the larger number of molecules

Question 21

in an equilibrium reaction, an increase in temperature will favour which reaction?

Answer 21

the endothermic

Question 22

in an equilibrium reaction, an decrease in temperature will favour which reaction?

Answer 22

the exothermic