2.2 Rates of Reaction

Rate of reaction

the change in concentration of a reactant or product per unit time

when is the rate fastest in a reaction

at the beginning as each reactant is at its highest concentration

why does rate slow down as the reaction proceeds

concentration of reactants decreases

how are rates measured

measuring the concentration of a reactant or product over a certain period of time

Factors which effect the rate of a reaction

surface area
concentration
temperature
pressure
light

catalyst

what must happen for a chemical reaction to occur

the reacting molecules have to collide with the correct force and direction

Activation energy

The minimum energy required for the reaction to occur

catalyst

a substance that increases the rate of a chemical reaction without being used up in the process. It does this by providing an alternative route of lower activation energy

homogenous catalyst

catalyst is in the same phase as the reactants

heterogenous catalyst

in a different phase from the reactants

e.g gases are adsorbed onto the metal surface and react. The products are then desorbed from the surface

Benefits of using enzymes as catalysts

they don’t harm fabrics and food

they are biodegradable

lower temperatures and pressures can be used, which saves energy and costs.

pure products are usually formed

How to measure change in volume of a gas

collect gas using a gas syringe

how to measure change in pressure during a reaction

manometer

How to measure change in mass during a reaction

using an accurate mass balance

how to measure change in colour during a reaction

using a colorimeter