Unit 1- Subtopic A Controlling the Rate

Question 1

How to increase the rate of reaction

Answer 1

1. Use of a catalyst
   2 Decrease particle size (increase surface area)
2. Increase temperature
3. Increase concentration
4. Increase pressure (gaseous reactants only)

Question 2

what is collision geometry

Answer 2

the angle at which particles collide with each other

Question 2

What does the rate of reaction depend on

Answer 2

1. The frequency of collisions
2. the energy of the reactant particles
3. collision geometry

Question 3

why does the rate of reaction decrease as time goes on

Answer 3

concentration of reactions decreases. This reduces the frequency of collisions between reactants so rate of reaction decreases.

Question 4

steeper the gradient

Answer 4

faster rate of reaction

Question 5

no slope

Answer 5

reaction is finished

Question 6

methods of measuring the rate of reaction

Answer 6

1. gas syringe
   2.. displacement of water (collecting a gas under water)
2. measuring mass lost

Question 7

why does decreasing particle size increase the rate of reaction

Answer 7

as particle size decreases, surface area increases. collisions take place on the surface so by having a larger surface area there is a greater chance of successful collisions so the rate of reaction increases

Question 8

why does increasing pressure increase the rate of reaction

Answer 8

moves particles closer together which increases the frequency of collisions. particles are more likely to react

Question 9

what states does increasing pressure work with

Answer 9

gas

Question 10

why will increasing pressure of solids or liquids not impact the surface area

Answer 10

particles are already as close as they can be

Question 11

what is the relative rate

Answer 11

the rate at any one particular point during a chemical reaction

Question 12

what is enthalpy

Answer 12

The energy content of substance

Question 13

what is enthalpy change

Answer 13

The change in energy content of a substance after a reaction

Question 14

formula for enthalpy change

Answer 14

Hp-Hr

Question 15

for an exothermic reaction

Answer 15

enthalpy change is always negative

Question 16

for endothermic reaction

Answer 16

enthalpy change is always positive

Question 17

what is the activated complex

Answer 17

unstable arrangement of atoms formed when reactant bonds start to break and product bonds start to form

Question 18

units for enthalpy change

Answer 18

kJmol-1

Question 19

if a reaction is endothermic what happens to the temperature

Answer 19

decrease which decreases the reaction rate

Question 20

if a reaction is exothermic what happens to the tempreture

Answer 20

increase which increases the reaction rate

Question 21

What happens if the reactants do not have energy greater than or equal to

Answer 21

The activated complex will fall back to the reactants

Question 22

What is temperature?

Answer 22

A measure of the average kinetic energy of the particles in a chemical

Question 23

What is the acyivation energy?

Answer 23

The activation energy is the minimum energy that particles need to collide successfully. Only particles with energy above this level have the potential to react

Question 24

What is an enzyme

Answer 24

a biological catalyst

Question 25

What is a catalyst

Answer 25

Speeds up a chemical reaction and remains chemically unchanged

Question 26

A catalyst is thought

Answer 26

to help in the formation of the activated complex by helping the particles collide with the correct geometry

Question 27

What does a catalyst do to the activation energy

Answer 27

lower it

Question 28

Lower activation energy makes it

Answer 28

easier to form the activated complex to form

Question 29

What is the effect of a catalyst on enthalpy change

Answer 29

no effect