C3 - Chemical Economics

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Rates of Reaction.

Collision Theory

When the temperature is increased the reacting particles have more energy and move fatser. This enables them to have more successful collisions per second because they will be colliding with more force.

When you increase the concentration (liquid) or pressure (gas) there will be more particles in a given space which means they are more likely to collide.

Temperature of Reactants

Chemical reactions happen when particles collide with enough energy.

In a reaction at a low temperature the particles move slowly and collide less often, at a lower energy meaning they won't be as successful. This means that the reaction is going to take longer.

At a high temperature the particles move faster and have more energy so they will collide more often at a higher energy. This means the reaction will that place faster.

Increasing the temperature causes an increase in kenetic energy. 

Concentration of the Reactants

In a reaction with the reactants at a low concentration the particles will be more spread out, so they won't collide as often.

In a reaction with the reactants at a high concentration the particles will be closer together and will collide more often. 

Increasing the concentration causes and increase in the number of particles in a specific space.

Pressure of a Gas

When a gas is under a low pressure the particles are more spaced out and will collide less often. 

When the pressure is high the particles become more crowded and will collide more often.

Surface Area of Solid Reactants

The larger the surface area of a reactant the faster the reaction will be because there is more surface for the particles to collide with. A powder will react more quickly than a lump becuase the power has lots of particles spaces out so there is more surface area. Whereas a lump is all stuck together so the surface area is smaller.

Using a Catalyst

A catalyst is a substance that changes the rate of a chemical reaction without being used up or chnaged at the end. Catalysts are often used to speed up a reaction. Catalysts work by lowering the activation energy of a reaction. A catalyst is specific to a certain reaction.

Reacting Masses

In a reaction mass is conserbed. Nothing is gained or lost, it's just re-aragned.

Relative Atomic Mass

Every element has its own relative atomic mass. On the periodic table the larger number is the relative atomic mass.

Relative Formula Mass

The relative formula mass of a compound is the sum of the relative atomic masses of all the atoms.

eg. H2O     2xH(1) = 2  +  1xO(16) = 16   =18(Relative Formula Mass)

Calculating Reacants and Products

To calculate how much substance a reaction will produce (product) or the amount of starting materials (reactant) you need, you need to remember that the total mass of the reactant always equals the total mass of the product, and the more reactants you start eith the greater the amount


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