reaction profiles

what must happen for atoms/ particles to react together in a chemical system?

For atoms or particles to react with each other in a chemical system they must first come into contact with each other in a collision

what are the 3 factors for analysing collisions?

• Energy

• Orientation

• Number of collisions per second

what is activation energy?

• , the minimum amount of energy required for the collision to be successful, that is for the particles to react together

This minimum amount of energy is called the activation energy and given the symbol Ea

how does activation energy compare in different chemical reactions?

Different reactions have different activation energies, depending on the chemical identities involved

how much energy would a reaction with higher activation require?

Reactions which have higher activation energies require more energy to start than those with lower activation energies

how many reactions have activation energy? why?

All reactions have an activation energy as the chemical bonds in the reactant molecules have to be broken first

what are energy profiles?

Energy profiles are graphical representations of the relative energies of the reactants and products in chemical reactions

what is displayed on the x and y axis of energy profiles?

• The energy of the reactants and products are displayed on the y-axis

• the progress of the reaction is shown on the x-axis

what do arrows on energy profiles indicate?

Arrows on the diagrams indicate whether the reaction is exothermic (downwards pointing) or endothermic (upwards pointing)

what represents the overall energy change of a reaction in energy profiles?

The difference in height between the energy of reactants and products represents the overall energy change of a reaction

describe this energy profile diagram of this exothermic reaction

• Energy is given out in exothermic reactions

  • The energy of the products will be lower than the energy of the reactants, so the change in energy is negative

  • This is represented on the energy profile with a downwards arrow as the energy of the products is lower than the reactants

describe this energy profile diagram of this endothermic reaction

• Energy is taken in in endothermic reactions

  • The energy of the products will be higher than the energy of the reactants, so the change in energy is positive

  • This is represented on the energy profile with an upwards arrow as the energy of the products is higher than the reactants