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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4:51 minutes

Problem 35

Textbook Question

All things being equal, would you expect a first-order reaction to be faster or slower than a second-order reaction?

Verified step by step guidance

Understand the rate laws for first-order and second-order reactions. A first-order reaction has a rate law of the form:

r = k [A]

, while a second-order reaction has a rate law of the form:

r = k {[A]}^{2}

r = k [A] [B]

Recognize that the reaction rate depends on both the rate constant (

k

) and the concentration of reactants. For a first-order reaction, the rate is directly proportional to the concentration of one reactant, while for a second-order reaction, the rate depends on the square of the concentration of one reactant or the product of two reactant concentrations.

Consider the effect of reactant concentration. At high concentrations, a second-order reaction can proceed faster than a first-order reaction because the rate depends on the square of the concentration or the product of two concentrations. However, as the concentration decreases, the rate of a second-order reaction decreases more rapidly than that of a first-order reaction.

Evaluate the role of the rate constant (

k

). The magnitude of

k

can vary depending on the specific reaction, so it is not possible to generalize whether a first-order or second-order reaction is inherently faster without knowing the value of

k

Conclude that all things being equal (e.g., similar concentrations and rate constants), a second-order reaction may initially be faster due to its dependence on higher powers of concentration, but it will slow down more quickly as the reactants are consumed compared to a first-order reaction.

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Key Concepts

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

Reaction Order

Reaction order refers to the power to which the concentration of a reactant is raised in the rate law of a chemical reaction. A first-order reaction depends linearly on the concentration of one reactant, while a second-order reaction depends on the square of the concentration of one reactant or the product of the concentrations of two reactants. Understanding reaction order is crucial for predicting how changes in concentration affect the rate of a reaction.

Rate Constant

The rate constant (k) is a proportionality factor in the rate law that is specific to a given reaction at a certain temperature. For first-order reactions, the rate constant has units of time⁻¹, while for second-order reactions, it has units of concentration⁻¹ time⁻¹. The value of the rate constant influences how quickly a reaction proceeds, with first-order reactions generally being faster due to their simpler dependence on concentration.

Half-Life

Half-life is the time required for the concentration of a reactant to decrease to half of its initial value. For first-order reactions, the half-life is constant and independent of concentration, while for second-order reactions, it increases with decreasing concentration. This difference in half-life behavior is significant when comparing the speed of reactions, as first-order reactions typically exhibit shorter half-lives, leading to faster overall reaction rates.

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Related Practice

Textbook Question

Identify the nucleophile and the electrophile in the following acid–base reactions:

Textbook Question

Within the following pairs, pick which reaction you would expect to be faster based on having a higher value of the frequency factor (A).

(b)

Textbook Question

For the following acid–base pairs, (vi) draw a reaction coordinate diagram.

(e)

Textbook Question

Parts (a)–(f) of this assessment refer to the rotation around the single bond of ethane.

Textbook Question

Parts (a)–(f) of this assessment refer to the rotation around the single bond of ethane.

(b) What is the order of the reaction with regard to ethane?

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?

Textbook Question

The reaction of tert-butyl chloride with methanol

is found to follow the rate equation

rate = k_r[(CH₃)₃C—Cl]

a. What is the kinetic order with respect to tert-butyl chloride?

Textbook Question

The reaction of tert-butyl chloride with methanol(CH3)3C—Cl Tert-butylchloride + CH3—OH methanol —> (CH3)C—OCH3 methyltert-butylether + HCl is found to follow the rate equation rate= Kt[(CH3)3C—Cl] a. What is the kinetic order with respect to tert-butyl chloride?

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