C6- the rate and extent of chemical changes

what is the collision theory

the more collisions there are the faster the reaction is. Particles have to collide with enough energy for the collision to be successful.

what is activation energy

the minimum amount of energy that particles need to react.

rate of reaction depends on four things

1. temperature

2. pressure/concentration

3. surface area

4. presence of a catalyst.

how does increasing temperature increase the rate of reaction

the particles move faster, so collide more frequently.

how does increasing pressure / concentration increase the rate of reaction

concentration- more particles in the same volume, will collide more frequently

pressure- the same number of particles occupy a smaller space, collide more frequently.

how does increasing the surface area increase the rate of reaction.

if one of the reactants is a solid then breaking it up into smaller pieces will increase its surface area to volume ratio.

how does a catalyst increase the rate of reaction

they all work by decreasing the activation energy by providing an alternate reaction pathway.

rate of reaction =

amount of reactant used or product formed / time

3 different ways of measuring the rate of a reaction

1. precipitation and colour change

2. change in mass

3. volume of gas given off

what is a reversible reaction?

a reaction where the products of the reaction can themselves react to produce the original reactants

what is equilibrium

the point at which the rates of the forward and backward reactions in a reversible reaction are the same, so the amounts of reactants and products in the reaction container don’t change

what does it mean is equilibrium lies to the right

the concentration of products is greater than that of the reactants

what is Le Chatelier’s principle

the idea that if you change the conditions of a reversible reaction at eqilibrium, the system will try to counteract that change

what are the three conditions that apply to Le Chateliers principle

1. temperature

2. pressure

3. concentration

le chalilliers principle - temperature

if you decrease temperature the equilibrium will move in the exothermic direction

if you raise the temperature, the equilibrium will move in the endothermic direction

Le Chateliers principle- pressure

if you increase the pressure the equilibrium tries to reduce it by moving in the direction that there are fewer molecules. and the opposite if you decrease pressure

Le Chateliers principle

if you change the concentration the system will no longer be a equillibrium. if you increase concentration the system tries to decrease it by making more products. if you decrease the concentration of products the system tries to increase it again by reducing the amount of reactants