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Reasoning in Kinetics

By roquerodriguez May 07, 2013 432 Words
Use the knowledge of kinetics to explain each of the following statements. a. An increase in temperature at which a reaction takes place causes an increase in reaction rate . An increase in temperature means increasing the energy of the molecules present. If the molecules has more energy , then more of the them will collide often with enough energy , to overcome the activation energy barrier. causing the reaction to proceed more quickly. b.An addition of the catalyst increases the rate at which the reaction will take place Catalyst are the one which provides alternate path way with the lower activation energy .If the activation energy is lowered ,then more molecular collisions will occur with enough energy to overcome the activation energy , causing the reaction to proceed more quickly. c. A catalyst that has been ground into powder will be more effective than a solid block of the same catalyst. An effectiveness of a solid catalyst depends on the surface area of the catalyst that is exposed to the reactants. Grinding a solid into powder greatly increases its surface area. d. An increase in the concentration of reactants increases the rate of the reaction. Increasing concentration of reactants crowds the reactants more closely together, making it more likely to collide with one another. The more collisions that occur , the more likely the collisions that will result in reactions will occur. 2. A(g)+B(g)→C(g)

The reaction above is second order with respect to A and zero order with respect to B. Reactants A and B are present in a closed container. Predict how each of the following changes to the reaction system will affect the rate constant and explain why. a. More gas A is added to the container .

b. More gas B is added to the container.
c. The temperature is increased.
d. The inert gas D is added to the container.
e. The volume of the container is decreased.
a.The rate of reaction will increase ,because the rate depends on the concentration of A as given in the rate law. Rate= K[A]2
However , the rate constant does not change , because the rate constant is independent of change in the concentration. b. Neither the rate nor the rate constant will change ,because, B is Zero order. c. The increase in temperature will increase the rate as well as the rate constant. d. Neither the rate nor the rate constant will change.

e. The rate of the reaction will increase, because decreasing the volume of the container will increase the concentration of A ,Rate= k[A]2

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