Topics: Chemical reaction, Kinetic theory, Reaction rate Pages: 3 (674 words) Published: February 11, 2013
1. Describe qualitatively, in terms of collision theory, the effect of concentration changes on the rate of reaction.

-If the concentrations of the reactants are increased, the rate of reaction also increases. -The molecules will be closer together and there is a greater chance of the molecules colliding. -Collisions will be more frequent-more collisions will occur in a certain length of time.

2. Explain why an increase in the pressure of a gas may increase the rate of reaction. When the pressure of a gas is increased, the molecules are pushed closer together. -The same number of molecules occupy a smaller volume.

-For a gaseous reaction, increasing the pressure is the same as increasing the concentration.

So, for (for both) a particular time MORE collisions will take place and there will be MORE collisions with energy GREATER than the activation energy. There will be MORE frequent collisions and the rate of reaction will INCREASE.

3. What is a catalyst?
A substance that increases the rate of chemical reaction without being used up in the process.

4. Explain how a catalyst gives rise to an increased rate of reaction. A catalyst lowers the activation energy of the reaction by providing an alternative route for the reaction to follow and this alternative route has a lower energy. This means less energy is needed for the reactions to happen when the collisions occur, so more reactions will happen.

5. Draw and enthalpy profile diagram for an exothermic reaction with and without a catalyst.

6. Describe the benefits of using catalysts in industry
Using catalysts reduce energy consumption and therefore cost, as less activation energy will be needed. Also with less energy required, less fossil fuel is burnt and less carbon dioxide is released into the atmosphere. Some catalysts make a process more effective, improving the percentage yield of an industrial preparation.

7. What is an enzyme? Why do enzymes...
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