Paper 2 - Rates of Reaction

Question 1

what does the collision theory state?

Answer 1

Chemical reactions can only take place when they reacting particles collide of each other. The collisions must have sufficient energy.

Question 2

overtime why do reactions slow down?

Answer 2

Because the number of reactant molecules is running out, which means we have a small number of collisions per second

Question 3

The more molecules in a reaction…?

Answer 3

The faster the rate of reaction and more collisions per second

Question 4

What is a hypothesis?

Answer 4

A proposal that could explain a fact or observation

Question 5

when is a measurement reproducible?

Answer 5

If it can be repeated by another person or using a different technique or equipment, and still get the same result

Question 6

what is one problem with the disappearing cross experiment?

Answer 6

Different people have different eyesight

Question 7

if a solid is in a solution, what can the particles in the solution only react with?

Answer 7

Can only react with the particles on the surface of the solid (on the outside of the solid)

Question 8

when does the rate of reaction increase?

Answer 8

When we increase the surface area of a solid reactant

Question 9

how to know if a reaction is exothermic?

Answer 9

The product has less energy than the reactant started with

Question 10

why does increasing the temperature increase the rate of reaction?

Answer 10

Because it increases the energy of the particles

Question 11

Catalyst?

Answer 11

increase the rate of chemical reactions but are not used up during the reaction

Question 12

How do catalysts help us to save money?

Answer 12

because they allow us to carry out reactions quickly without needing to increase the temperature

Question 13

Can we re use catalysts?

Answer 13

yes because they are not used up in the reaction

Question 14

How do catalysts increase the rate of reaction?

Answer 14

by providing a different pathway for the reaction that has a lower activation energy (particles require less energy so more particles can collide per second)

Question 15

why do we not include catalysts in the chemical equation for a reaction?

Answer 15

Because they are not used up in the reaction

Question 16

Reversible reaction?

Answer 16

this reaction had a different kind of arrow, showing that the products can react to change back to the original reactants

Question 17

How can we change the direction of reversible reactions?

Answer 17

changing the conditions e.g. heat, cooling

Question 18

What happens in the reverse reaction?

Answer 18

energy is released so it is exothermic

Question 19

if a reversible reaction is exothermic in one direction…?

Answer 19

it is endothermic in the opposite direction

Question 20

equilibrium?

Answer 20

at some point, the forward and the reverse reactions will take place at exactly the same rate

Question 21

Le Chatelier’s Principle?

Answer 21

if a reaction is at equilibrium and a change is made to the conditions, then the system responds to counteract the change

Question 22

What happens if we change the concentration of the reactants or products?

Answer 22

then the reaction is no longer at equilibrium

Question 23

What does the pressure of gas depend on?

Answer 23

The number of molecules

Question 24

What happens if we increase the pressure on a reversible reaction at equilibrium?

Answer 24

The position of the equilibrium to the side with the smaller number of molecules
e.g. in a reaction, if 4 molecules are on one side of the reaction, and 2 on the other, the position will shift to the 2 molecules

Question 25

When does changing the pressure have no effect on the equilibrium?

Answer 25

when there is the same number of molecules on each side of the reaction