Rates of Reactions – Flashcards

The amount of a reactant of product used up or produced in a unit of time

We monitor the change in concentration of either reactant of the products over a unit of time.

For a reaction to take place, the particles of the reactants much collide with one another. The colliding particles must have sufficient energy to react, this energy is known as activation energy. Collisions of particles that have overcome their bonds and required activation energy are called successful collisions.

It is necessary to increase the frequency of successful collisions. i.e. more successful collisions need to take place every second.

the concentration of a reactant the temperature of at which the reaction takes place the surface area of the reactant the addition of a catalyst

Increasing the concentration of a reactant increases the number of particles of reactant in the given volume (of a liquid or gas). Therefore the reacting particles will collide more often and there is a greater chance that particles will collide and have successful collisions.

Increasing the temperature increases the average kinetic energy of the reactant particles and therefore more of the collisions that take place will have the necessary activation to react. Hence there will be more successful collisions per second. Every 10° increase the rate of reaction doubles.

Thus if you increase the surface area of the solid, there will be more particles of the solid exposed to the other reactant. Hence, there will be more successful collisions per second.

The iron powder(iron fillings) immediately burn and produce yellow - orange sparks.

A catalyst is a substance that increases the rate of a chemical reaction without being chemically unchanged at the end of the reaction. They never produce more product. They just produce the same amount more quickly.

Catalysts work by offering an alternative pathway to lower activation energy. This means that more of the collisions taking place will have the necessary activation energy. Hence there will be more successful collisions per second.

Transition Metals such as Nickel, Iron Platinum

The minimum amount of energy needed for the particles to react.

the frequency of collisions between particles. the energy with which particles collide.

Amount of product formed or reactant used up / time

In the production of margarine (hydrogenation of vegetable oils.)

In the production of ammonia from nitrogen and hydrogen. (the Haber process.)

In catalytic converters of car exhausts. It catalyses the conversion of carbon monoxide and nitrogen oxide into the less polluting carbon dioxide and nitrogen.

Products can be made more quickly, saving time and money. The catalysts reduce the need for high temperatures, saving fuel and reducing pollution.

Special types of protein called enzymes.

As living cells use chemical reactions to produce new materials. To do this quickly and effectively they use biological catalysts called ENZYMES.

Enzymes are large protein molecules which contain an area where a chemical reaction can take place;

At a temperature of around 37 Deg C (Body Temperature) as at high temperatures they are de-natured.

Different enzymes operate best at different pH values, so pH can also de-nature an enzyme if it is the incorrect one for a particular enzyme.