Chemistry AQA iGCSE Chapter- 8

Chemistry AQA iGCSE Chapter- 8

1. C8.1 How fast?

   • We can find out the rate of the chemical reaction by following the amount of reactants used over some time.
     • RoR= Amount of reactant used/ time
   • We can also found out the rate of a chemical reaction by following the amount of products being made over time.
     • RoR=Amount of product formed/ time
   • The slope of any line of the graph at any given time tells us the rate of the reaction. The steeped the slope, the faster the reaction.

2. C8.2 Collision theory and surface area.

   • Main Factors that affect rates of reaction
     • Temperature
     • Surface Area
     • Concentration of solutions or pressure of gas.
     • presence of catalyst
   • Collision Theory
     • Particles must collide with each other with a certain minimum amount of energy before they can react.
     • Activation energy
       • The minimum amount of energy that particles must have before they can react
   • The rate of a chemical reaction increases if the surface area of any solid reactant increases. This increases the frequency of collisions between reacting particles.

3. C8.3 The effect of temperature.

   • As temperature increases, the rate of reaction increase too.
     • because particle collide more frequently with more energy as higher proportion of particles have energy higher than the activation energy.

4. C8.4The effect of concentration or pressure.

   • Increasing the concentration of the solution or pressure of gas increases the rate of reaction
     • because there are more particles closer to each other therefore there will more collisions for a reaction to occur.

5. C8.5 the effect of catalysts

   • A catalysts changes the rate of reactions but does not change the products. It is unaffected.
   • Different catalysts are used for different reactions
     • Usually used in industry to speed reactions up and reduce energy costs and help the environment
       • usually transition metal such as gold, platinum and palladium
         • Iron for ammonia and platinum for nitric acid
         • Used in the form of powders, pellets or fine gauzes to give them most possible surface area and makes the more effective.