CHEM 112 Chapter 14: Chapter 14 Section 5

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redant354

6 Feb 2019

School

UMASS-Amherst

Department

Chemistry

Course

CHEM 112

Professor

Prof. Scott M. Auerbach

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Document Summary

When other reaction conditions are held constant, all reactions proceed mroe rapidly as temperature increases. All reactions have an activation barrier (an energy that must be overcome fore reactants to proceed to form products) and changing the temperature affects the ability of reactants to overcome this barrier. Reaction coordinate diagram: plot that shows energy as a function of the progress of the reaction from reactants to products. Activated complex/ transition state: conversion of reactants to products passes through a high-energy state. Activation energy, ea: energy required to reach this transition state. If some minimum amount of energy is required for the conversion of reactants to products, increasing the temperature will increase the number of molecules that have that minimum energy. If two similar reactions with the same delta e are run at the same temperature, the one with the larger activation energy will be slower. When the temperature of a reaction is increased, the rate of the reaction increases.

Related Questions

Theoretical Models for Chemical Kinetics and Reaction Profiles

Chemical reactions involve the making and breaking of chemical bonds. Since different types of bonds have different bond strengths, the energy of the reacting system changes as the reaction progresses. A graph that shows the change in energy as a function of the progress of the reaction is known as a reaction profile.

According to the theories of chemical reactions, when molecules collide in the correct orientation with a sufficient amount of energy, an activated complex or transition state is formed. The reaction then proceeds and the activated complex decomposes into products.

Part A

Observe the following reactants and predict which of the following may form the potential products given the values for the energy of activation, Ea, and enthalpy of the reaction, ÎH, in combination with the molecular orientation.

Check all that apply.

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Part B

The progress of a reaction is determined by various steps involving energy changes with respect to collision theory. Identify the key features of the reaction profile below.

Drag the appropriate labels to their respective targets in the energy profile diagram.

Hydrogen peroxide decomposes into water and oxygen by thefollowing reaction:

2 H2O2(aq) ? 2 H2O(l) + O2(g) ?Hrxn = -94.64 kJ/mol

Experimental evidence tells us that this reaction is first orderwith respect to hydrogen peroxide, with an activation energy of75.3 kJ/mol at 300 K.

(A.)What is the activation energy for the reverse reaction?

(B.)Sketch the reaction pathway below. Be sure to label the axes,reactants, products, transition state, and energies.

(C.)Assuming the forward and reverse reaction have the samefrequency factor, what is the equilibrium constant for thisreaction?

Catalase is an enzyme found in nearly all living organisms thatcatalyzes the hydrogen peroxide decomposition reaction shown aboveby lowering the activation energy of the forward reaction to 8.8kJ/mol.

(D.)How many times faster does hydrogen peroxide decompose inthe presence of catalase?

(E.)What temperature would we need to decompose hydrogen peroxodeat to achieve the same rate increase achieved with catalase?

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CHEM 112 Chapter 14: Chapter 14 Section 5

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