8. (a) Define the rate of a chemical reaction - Leaving Cert Chemistry - Question 8 - 2004
Question 8
8. (a) Define the rate of a chemical reaction.
Explain why increasing the temperature has a significant effect on the rate of a reaction.
(b) The diagram shows a r... show full transcript
Worked Solution & Example Answer:8. (a) Define the rate of a chemical reaction - Leaving Cert Chemistry - Question 8 - 2004
Step 1
Define the rate of a chemical reaction.
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Answer
The rate of a chemical reaction is defined as the change in concentration of a reactant or product per unit time, typically expressed in mol/L/s.
Step 2
Explain why increasing the temperature has a significant effect on the rate of a reaction.
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Answer
Increasing the temperature increases the kinetic energy of the molecules involved in the reaction. This results in a greater number of collisions between reactant molecules. More collisions exceeding the activation energy lead to a higher frequency of effective collisions, thus accelerating the reaction rate.
Step 3
Name the quantities of energy marked A and B.
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Answer
A: Activation energy
B: Heat of reaction
Step 4
Copy this diagram into your answer book and indicate clearly on your diagram the likely effect of adding a catalyst on the energy profile for the reaction.
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Answer
When adding a catalyst, the activation energy of the reaction decreases, which can be illustrated by a lower peak on the reaction profile diagram.
Step 5
Name two elements used as catalysts in catalytic converters.
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Answer
Platinum and palladium.
Step 6
Name one substance which poisons the catalyst in a catalytic converter.
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Answer
Lead compounds.
Step 7
State the observations you would make when carrying out this experiment.
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Answer
The solution will change color, and there may be bubbling or fizzing, indicating gas production during the reaction.
Step 8
Explain how these observations provide evidence for the intermediate formation theory.
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Answer
The color change from pink to green indicates the formation of a new substance, suggesting an intermediate is present. Bubbling indicates that a gas is produced, which further supports the idea of an intermediary reacting before forming the final product.
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