kinetics

Question 1

what is the collision theory?

Answer 1

for a chemical reaction to occur, the particles need to collide with enough energy (with the required activation energy) and with the right orientation

Question 2

why is the activation energy for an endothermic reaction relatively higher than the activation energy for an exothermic reaction?

Answer 2

in exothermic reactions the reactants are higher in energy tha the products.
in exothermic reactions, the reactants are lower in energy than the products

Question 3

what is collision frequency

Answer 3

the number of collisions per unit of time

Question 4

5 factors which increase the rate of a reaction and why?

Answer 4

-increasing concentration of (aq): higher number of reactant molecules per unit volume so a higher frequency of successful collisions
-increasing pressure (g): higher number of reactant molecules per unit volume so a higher frequency of successful collisions
- increasing surface area (s): more reactant is exposed so higher frequency of successful collisions
- increasing temperature: reactant molecules gain kinetic energy, have more suffiecient energy to react (have the required activation energy) so there’s a higher frequency of successful collisions
- using a catalyst: lowers the activation energy so more reactant particles have sufficient energy (minimum activation energy) to react so there’s a higher frequency of successful collisions

Question 5

what does the area under the maxwell-boltzmann distribution curve represent?

Answer 5

the total number of reactant molecules (remains constant)

Question 6

draw and label a maxwell-boltzmann distribution curve

Answer 6

see paper

Question 7

do most collisions result in a reaction?

Answer 7

no

Question 8

define activation energy

Answer 8

the minimum energy that particles must collide with for a reaction to occur

Question 9

what happens to the maxwell-boltzmann curve when you increase the concentration of reactants ?

Answer 9

curve shifts up (the area under the curve increases because there’s more reactants but the proportion is relatively the same)

Question 10

draw a maxwell-distribution curve for increased concentration

Answer 10

see paper

Question 11

draw a maxwell-distribution curve for increased temperature

Answer 11

see paper

Question 12

draw a maxwell-distribution curve for decreased temperature

Answer 12

see paper

Question 13

draw a maxwell-distribution curve for when you add a catalyst

Answer 13

see paper

Question 14

what happens to the maxwell-boltzmann curve when you increase the temperature ?

Answer 14

curve shifts right and down (the same number of reactant particles but proportion changes)

Question 15

what happens to the maxwell-boltzmann curve when you decrease the temperature ?

Answer 15

shifts left and up (same number of reactant particles but proportion changes)

Question 16

what happens to the maxwell-boltzmann curve when you add a catalyst?

Answer 16

curve stays the same but position of activation energy line shift left as more particles will have the required activation energy to collide and react

Question 17

what is the rate of a reaction?

Answer 17

the change in the amount or concentration of a reactant or product per unit of time

Question 18

how do catalysts work?

Answer 18

a catalyst increases the reaction rate without being used up in the process by providing an alternative reaction route with a lower activation energy

Question 19

two types of catalysts?

Answer 19

homogenous: catalyst in the same phase as the reactant molecules
heterogenous: catalyst in a different phase to the reactant molecules