Energy Level Diagrams

How to draw energy level diagrams

Multiple Select

Enthalpy Arrow down means

• exothermic reaction

• temperature decreases

• temperature increases

• endothermic reaction

​Basic Diagram

When drawing energy level diagrams you need to show the following:
-energy level for the reactants, their names or formulae
-energy level for the products, their names or formulae
- an arrow down to show the energy lost -Δ H
- OR an arrow up to show the energy gained Δ H

Draw

Draw an energy profile diagram for this reaction:

Mg(s) + 2HCl(aq)--> MgCl₂ (aq) + H₂(g) + energy

[4 marks]

All reactions need to overcome activation energy, this energy is needed to break the bonds of all of the reactants.
This is absorbed so the arrow goes up.

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​Activation energy

Once all of the bonds are broken, new bonds of the reactants can form. Forming bonds is exothermic.
Energy in - energy out = energy change

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​Another arrow

Open Ended

If the activation energy is 30kJ/mol, and 35KJ/mol is released when new bonds are made, what is the magnitude of the energy change?

Multiple Choice

How can the activation energy of a reaction be lowered?

• increase the surface area of the solid reagents

• increase the temperature

• increase the concentration of the reagent

• add a catalyst

Multiple Select

Which of these do NOT apply to a catalyst ?

• speeds up a reaction

• lowers the activation energy

• is used up

• is chemicallu changed by the reaction

Draw

Add a curved line to show the progress of reaction and and an arrow to show the activation energy for a catalysed reaction.

Draw

Draw an energy profile for an exothermic reaction, both catalysed and uncatalysed. Add arrows and label them to show the activation energies and the energy change Δ H.

Open Ended

Cold packs are used to treat sports injuries. A pack contains water and ammonium nitrate crystals. When the compartments are broken the reactants are mixed and rapid cooling takes place.

Explain in terms of bonds broken and bonds formed why this process takes in heat.

Draw

Cold packs are used to treat sports injuries. A pack contains water and ammonium nitrate crystals. When the compartments are broken the reactants are mixed and rapid cooling takes place.

Draw an energy level diagram to show the process occurring in the cold pack. Explain your diagram.

Poll

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Open Ended

Any questions that you want to ask?