Rates of Reaction

affected by:

• concentration
• pressure
• a catalyst
• intensity of radiation
• surface area
• particle size
• temperature

For a reaction to occur, reactant particles must collide AND their combined kinetic energy must be equal to or greater than the activation energy for the reaction.

increasing CONCENTRATION/ PRESSURE:

• means more particles per cm³
• hence, more collisions per second
• hence, rate of reaction INCREASES

! no mention of activation energy !

increasing TEMPERATURE:

• particles have more kinetic energy
• so collisions have more knietic energy
• collisions occur more frequently
• as a greater proportion of collisions will equal or exceed the minimum activation energy needede to react
• hence, the rate of reaction INCREASES

addition of a CATALYST:

• provides an alternative pathway for the making and breaking of bonds
• hence, providing a lower activation energy
• so a greater proportion of collisions will equal or be greater than the minimum activation energy needed for the reaction to occur
• hence, the rate of reaction INCREASES

• The minimum combined kinetic energy required by a pair of colliding particles before a reaction will occur.

or

• The energy required to allow bonds in the reactants to stretch and break as the new bonds form in the products.