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Ch.14 - Chemical Kinetics
All textbooksBrown 14th EditionCh.14 - Chemical KineticsProblem 51
Chapter 14, Problem 51

(c) Which factor is most sensitive to changes in temperature—the frequency of collisions, the orientation factor, or the fraction of molecules with energy greater than the activation energy?

Verified step by step guidance
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Understand the three factors involved in the rate of a chemical reaction: the frequency of collisions, the orientation factor, and the fraction of molecules with energy greater than the activation energy.
The frequency of collisions refers to how often molecules collide with each other. This is generally influenced by concentration and temperature, but it is not the most sensitive to temperature changes.
The orientation factor, also known as the steric factor, relates to the spatial arrangement of molecules during collisions. While important, it is typically less sensitive to temperature changes compared to other factors.
The fraction of molecules with energy greater than the activation energy is described by the Arrhenius equation. This factor is highly sensitive to temperature changes because even a small increase in temperature can significantly increase the number of molecules that have enough energy to overcome the activation energy barrier.
Conclude that the fraction of molecules with energy greater than the activation energy is the most sensitive factor to changes in temperature, as it exponentially increases with temperature according to the Arrhenius equation.

Key Concepts

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

Collision Theory

Collision theory explains how chemical reactions occur and why reaction rates differ for various reactions. It posits that for a reaction to take place, reactant molecules must collide with sufficient energy and proper orientation. The frequency of these collisions is influenced by temperature, as higher temperatures increase molecular motion, leading to more frequent and energetic collisions.
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Collision Theory

Activation Energy

Activation energy is the minimum energy required for a chemical reaction to occur. It represents the energy barrier that must be overcome for reactants to transform into products. As temperature increases, a greater fraction of molecules possess energy exceeding this threshold, which significantly affects the reaction rate and is a key factor in determining how sensitive a reaction is to temperature changes.
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Activity Series Chart

Arrhenius Equation

The Arrhenius equation quantitatively describes how the rate constant of a reaction depends on temperature and activation energy. It shows that as temperature increases, the rate constant increases exponentially due to a higher fraction of molecules having sufficient energy to overcome the activation energy barrier. This relationship highlights the sensitivity of reaction rates to temperature changes, particularly through the fraction of molecules with adequate energy.
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Related Practice
Textbook Question

The gas-phase decomposition of NO2, 2 NO2(g) → 2 NO(g) + O2(g), is studied at 383°C, giving the following data:

Time (s) [NO2] (M)

0.0 0.100

5.0 0.017

10.0 0.0090

15.0 0.0062

20.0 0.0047 

(a) Is the reaction first order or second order with respect to the concentration of NO2?

(c) Predict the reaction rates at the beginning of the reaction for initial concentrations of 0.200 M, 0.100 M, and 0.050 M NO2.

Textbook Question

Sucrose 1C12H22O112, commonly known as table sugar, reacts in dilute acid solutions to form two simpler sugars, glucose and fructose, both of which have the formula C6H12O6. At 23 C and in 0.5 M HCl, the following data were obtained for the disappearance of sucrose: Time (min) 3C12H22o11 4 1M2 0 0.316 39 0.274 80 0.238 140 0.190 210 0.146 (a) Is the reaction first order or second order with respect to 3C12H22O114?

Textbook Question

(a) What factors determine whether a collision between two molecules will lead to a chemical reaction?

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Textbook Question

(b) Does the rate constant for a reaction generally increase or decrease with an increase in reaction temperature?

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