U1 KA4 - controlling the rate

Question 1

what is meant by collision theory?

Answer 1

for a chemical reaction to occur, the reactant molecules must collide with enough energy

Question 2

what is the activation energy?

Answer 2

the minimum kinetic energy required for a successful collision to occur

Question 3

what is meant my collision geometry?

Answer 3

the reactant molecules must be facing the right way for a successful collision to take place, so that the activated complex can be formed

Question 4

an increase in successful collision causes an increase in…

Answer 4

reaction rate

Question 5

what are the stages of a reaction?

Answer 5

1 - bonds start to break
2 - activated complex
3 - product molecule forms

Question 6

describe the first stage in a chemical reaction

Answer 6

as the reactant molecules collide, they must have enough energy to overcome the repulsive forces and start to break the bonds between the atoms

Question 7

describe the second stage in a chemical reaction

Answer 7

the intermediate stage is reached, in which a high energy, unstable arrangement of atoms is formed called the activated complex

Question 8

describe the third stage in a chemical reaction

Answer 8

energy is given out as new bonds are formed and the atoms are rearranged into the product molecules

Question 9

average rate formula

Answer 9

average rate = change in quantity/change in time

Question 10

relative reaction rate formula

Answer 10

1/t

Question 11

what apparatus is used to collect soluble gases?

Answer 11

gas syringe

Question 12

what apparatus is used to monitor the mass lost during a chemical reaction?

Answer 12

a balance

Question 13

what method is used to collect insoluble gases?

Answer 13

collection over water (downward displacement of water)

Question 14

factors affecting the rate of a reaction?

Answer 14

temp
concentration
particle size
use of catalyst

Question 15

describe how increasing temp affects reaction rate

Answer 15

particles have more energy and so move more quickly

increasing the temp increases the rate of the reaction because the particles collide more often

Question 16

describe how increasing the concentration of reactants affects the reaction rate

Answer 16

more reactant particles moving together
there will be more collisions so the reaction rate is increased
the higher the concentration of reactants the faster the rate of a reaction will be

Question 17

describe how decreasing the particle size of a reactant affects the reaction rate

Answer 17

surface area is increased so more collisions can take place, increasing the rate of reaction

Question 18

describe how the use of a catalyst affects the reaction rate

Answer 18

alters the rate of a reaction allowing it to be done at a lower temp + lowers the activation energy

Question 19

what is an exothermic reaction?

Answer 19

heat is given out

the products will have less energy than the reactants

Question 20

what is the enthalpy change?

Answer 20

the quantity of energy given out

Question 21

what is an endothermic reaction?

Answer 21

heat is absorbed

the products will have more energy than the reactants

Question 22

if a reaction has low activation energy then the reaction rate will be…

Answer 22

fast

Question 23

if a reaction has high activation energy then the reaction rate will be…

Answer 23

slow