PR Diagrams

PE Diagrams

By NAUDIA LAWRENCE

A potential energy diagram plots the change in potential energy that occurs during a chemical reaction.

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Potential Energy Diagrams

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Exothermic = Downhill as enegy is lost

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Endothermic is uphill as energy is absorbed or put in​

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​Reactions are uphill or downhill

Multiple Choice

• Expthermic

• Endothermic

Multiple Choice

• Expthermic

• Endothermic

Multiple Choice

• Expthermic

• Endothermic

Multiple Choice

• Exothermic

• Endothermic

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You will be asked about the parts of the energy diagram on your exam.

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Let us look at what they are.​

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Parts of the reaction

A and B are reactants

The energy of reactants is measured from 0 - 40 kJ on the ​y axis

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​Energy of reactants

C and D are reactants

The energy of the products is measured from 0 - 20 kJ on the ​y axis

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​Energy of Product

Multiple Choice

What is the energy of the products in this reaction?

• 10 kJ

• 50 kJ

• 100 kJ

• 250 kJ

Multiple Choice

What is the energy of the reactants in this reaction?

• 10 kJ

• 50 kJ

• 100 kJ

• 250 kJ

Parts of the reaction

What is Activation Energy?

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To ACTIVATE means to get started.

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The activation energy is the energy it takes to get the reaction started.

Without this energy the reaction will not happen​

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Activation Energy

To ACTIVATE means to get started.

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The activation energy is the energy it takes to get the reaction started.

Without this energy the reaction will not happen​

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Activation Energy

Parts of the reaction

This is a high enegy state where all the atoms combine together before they reange into the products

The Activated complex

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​The activated complex is the highest point on the graph

Parts of the reaction

​When using a catalyst the activation energy is made smaller. This means that the reaction can go faster at the same temperature. amount of a catalyst is needed.

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Using a Catalyst

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The catalyst does not change the energy of the reagents or the products. Also, the catalyst does not change in the reaction.

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Using a Catalyst

Heat of Reaction, ΔH

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This is the energy that is absorbed by the reaction of given off.

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It is the difference between the reactanrs and products​

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​Heat of Reaction

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ΔH

is negative for exothermic reactants​

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ΔH

is positive for endothermic reactants​

Parts of the reaction

Use your note sheet to help you answer the following quesyions

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Multiple Choice

Does the graph represent an endothermic or exothermic reaction?

E

• Endothermic

• Exothermic

Multiple Choice

Determine the heat of reaction, DH,  for this reaction.

• 200 kJ

• 100 kJ

• 50 kJ

• 150kJ

Multiple Choice

Determine the activation energy, Ea for this reaction.

• 200 kJ

• 100 kJ

• 250 kJ

• 50 kJ

Multiple Choice

What is the energy of the activated complex for this reaction?

• 200 kJ

• 100 kJ

• 250 kJ

• 150 kJ

Draw

The balanced equation below represents the reaction between carbon monoxide and

oxygen to produce carbon dioxide.

2CO(g) + O2(g) → 2CO2(g) + energy

On the potential energy diagram in your answer booklet, draw a double-headed arrow (b) to indicate the interval that represents the heat of reaction.

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​Duplicate this text as many times as you would like.

​All provided templates can be reused multiple times.

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Draw

A 1.00-mole sample of glucose, C₆H₁₂O₆, completely reacts with oxygen, as represented

by the balanced equation below.

C₆H₁₂O₆(s) + 6O₂(g) → 6CO₂(g) + 6H₂O(ℓ) + energy

Using the axes in your answer booklet, complete the potential energy curve for the

reaction of glucose with oxygen.

Draw

One process used to manufacture sulfuric acid is called the contact process. One step

in this process, the reaction between sulfur dioxide and oxygen, is represented by the

forward reaction in the system at equilibrium shown below.

2SO₂(g) + O₂(g) ---> 2SO₃(g) + 394 kJ

On the labeled axes in your answer booklet, complete the potential energy diagram for the forward reaction represented by this equation.

Draw

Hydrocarbons and fissionable nuclei are among the sources used for the production of energy in the United States. A chemical reaction produces much less energy than a nuclear reaction per mole of reactant. The balanced chemical equation below represents the reaction of one molecule of a hydrocarbon with two molecules of oxygen.

Chemical equation: CH₄ + 2O₂ → CO₂ + 2H₂O + 1.48 × 10⁻¹⁸ J

On the labeled axes in your answer booklet, draw a potential energy diagram for the reaction of the hydrocarbon with oxygen.