Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

6. Thermodynamics and Kinetics

Energy Diagram

Organic Chemistry

6. Thermodynamics and Kinetics

Energy Diagram

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2:26 minutes

Problem 13a

Textbook Question

When a small piece of platinum is added to a mixture of ethene and hydrogen, the following reaction occurs: Ethene

Doubling the concentration of hydrogen has no effect on the reaction rate. Doubling the concentration of ethene also has no effect.
a. What is the kinetic order of this reaction with respect to ethene? With respect to hydrogen? What is the overall order?

Verified step by step guidance

Step 1: Analyze the reaction provided. The reaction involves ethene (C₂H₄) reacting with hydrogen (H₂) in the presence of a platinum catalyst to form ethane (C₂H₆). This is a catalytic hydrogenation reaction where the double bond in ethene is converted into a single bond in ethane.

Step 2: Understand the experimental observation. Doubling the concentration of ethene or hydrogen has no effect on the reaction rate. This indicates that the reaction rate is independent of the concentrations of these reactants.

Step 3: Recall the concept of reaction order. The kinetic order of a reaction with respect to a reactant is determined by how the rate of reaction changes with the concentration of that reactant. If the rate does not change when the concentration of a reactant is altered, the reaction is zero-order with respect to that reactant.

Step 4: Determine the kinetic order for each reactant. Since the rate is unaffected by changes in the concentration of ethene, the reaction is zero-order with respect to ethene. Similarly, since the rate is unaffected by changes in the concentration of hydrogen, the reaction is zero-order with respect to hydrogen.

Step 5: Calculate the overall order of the reaction. The overall order of a reaction is the sum of the orders with respect to each reactant. Since the reaction is zero-order with respect to both ethene and hydrogen, the overall order of the reaction is 0.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Kinetics and Reaction Order

Kinetics is the study of the rates of chemical reactions and the factors that affect them. The reaction order refers to the power to which the concentration of a reactant is raised in the rate law. It indicates how the rate of reaction is affected by the concentration of reactants. In this case, since doubling the concentrations of both ethene and hydrogen does not change the reaction rate, the reaction is zero-order with respect to both reactants.

Catalysis

Catalysis involves the acceleration of a chemical reaction by a substance called a catalyst, which is not consumed in the reaction. In this scenario, platinum acts as a catalyst for the hydrogenation of ethene to ethane. The presence of the catalyst lowers the activation energy required for the reaction, allowing it to proceed more quickly without affecting the overall stoichiometry or the reaction order.

Zero-Order Reactions

A zero-order reaction is one where the rate of reaction is constant and independent of the concentration of the reactants. This means that changes in the concentration of the reactants do not affect the rate of the reaction. In the context of the question, since increasing the concentrations of ethene and hydrogen does not alter the reaction rate, it indicates that the reaction is zero-order with respect to both reactants, leading to an overall zero-order reaction.