Rates of Reaction
- Knowing and controlling the rate of chemical reactions is important in living cells, in the laboratory and in industry.
- We can measure the rate of a chemical reaction by following the rate at which the reactants are used up.
- Alternitively, we can measure the rate at which products are made.
- The minimum amount of energy that particles must have in order to react is called the activation energy.
- The rate of a reaction increases if the surface area of any solid reactant increases.
- Four main factors affect the rate of chemical reactions:
Temperature, Concentration or Pressure, Surface area, and the presence of a catalyst.
The effect of temperature
- Reactions happen more quickly.
- A 10 degree increase in temperature at room temperature roughly doubles the rate of a reaction.
- The rate of a chemical reaction increases with temperature because the particles collide more often and they have more energy.
The effect of concentration
- Increasing the concentration of reactants increases the frequency of collisions between particles, increasing the rate of reaction.
- Increasing the pressure of reacting gases results in particles colliding more often, increasing the rate of reaction.
The effect of catalysts
- A catalyst speeds up the rate of a chemical reaction.
- They are often very expensive, because they are made from precious metals. However, it is often cheaper to use a catalyst than to pay for the energy needed for higher temperatures or pressures in a reaction.
- A cataylst is NOT used up during a chemical reaction. It merely provides a surface for the reacting particles to come together.