Rates of Reaction

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Rates of Reaction

The rate of a reaction can be defined as the speed at which a reactant is lost, and/or the speed at which a product is formed in a chemical reaction. All chemical reactions happen at different rates. Explosions are extremely fast, whereas rusting is extremely slow. There are five factors that affect the rate of a reaction. These are:

  • Temperature
  • Surface Area/Particle Size
  • Pressure
  • Concentration
  • Catalysts

In our everyday lives, we usually want to slow reactions down, rather than speed them up. For example, we store food in fridges or freezers to slow any reactions down which would otherwise make the food rot. Aging is a process that many people want to slow down. Scientists have blamed the appearance of wrinkles on free radicals in the skin. They have also found out that using antioxidant creams helps slow the aging of skin down. Some paints contain antioxidants, called corrosion inhibitors, which slow down the oxidation of iron.

The Collision Theory

        This kinetic theory will help me to explain the factors affecting the rate of a reaction. Firstly, reactions only occur when two reactants collide with each other with sufficient energy (i.e. more than the activation energy (Ea)). If there is not enough energy for a reaction to be activated, the bonds within the reactants will not break and they will simply bounce off each other. Therefore very few substances will react at room temperature because they do not have sufficient energy. This is why most substances have to be heated for a reaction to occur.

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        Below is a typical energy diagram, displaying the activation energy:

Changing Certain Factors

Temperature – The Collision Theory states that as temperature increases, so does the rate of reaction. This is because the reactant particles have more energy, which causes them to move faster. This causes more collisions with energy greater than the activation energy, causing the rate to increase.

Surface Area/Particle Size – As surface area increases/particle size decreases, the rate increases. This is because there are more solid particles or total surface area ...

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