# Energetics-Unit 2

• Created by: Heather
• Created on: 07-05-15 19:57
What is the definition of the activation energy?
The minimum energy required for a reaction to occur,
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What two things need to happen for a collision to be successful and lead to a reaction?
-Correct orientation of molecules, -Equal to or greater than the activation energy,
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What are the graphs called which show the distribution of energies in a reaction?
Maxwell- Boltzmann distribution,
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What are the two headings for the x-axis and y-axis?
x-axis= Energy. y axis= Number of molecules,
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What does the area under the curve represent?
The total number of molecules in the sample,
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Why does the curve start at the origin?
As there are no molecules with zero energy,
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What is the Emp and where is it found on the graph?
-The most probable energy, -The maximum of the curve indicated,
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If the temperature is increased, describe the effect on the Emp and average energy?
Both would increase
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What is the definition of the rate of a reaction?
The change in concentration of a substance in a given time/ in unit time,
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On a graph where the concentration of the reagent is given against time, what shows the rate of the reaction?
The gradient pf the graph at that time,
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What 5 reasons affect the rate of a reaction?
-Concentration of reagents in solution, -Pressure of gaseous reactants, -Surface area of any solid reagent, -Temperature, -Presence of a catalyst,
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Describe how the rate of a reaction is affected by concentration?
-Increasing the concentration of a reagent increase the number of particles in a given volume and so increases the collision rate, and hence the chance of productive collisions,
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Why does the rate of the reaction decrease over time?
As the reagents are being used up so their concentrations fall. The gradient falls to zero at completion,
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Describe how the rate of a reaction is affected by the increase in surface area?
As the surface area of the solid increases, it allows more collisions to occu with particles of the other reagent.
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Describe how an increase in temperature affects the rate of a reaction?
The mean kinetic energy of particles increases so particles have more energy and therefore, mroe particles have equal to or greater than the minimum energy so there are more successful collisions,
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What is the definition of a catalyst?
A substance which increases the rate of a reaction without itself being used up in the process,
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How do catalysts work?
They provide an alternative route for reactants which has a lower activation energy needed for a successful collision to lead to a reaction,
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Does a catalyst have an effect on the equilibrium?
No but does help the reach equilibrium faster,
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## Other cards in this set

### Card 2

#### Front

What two things need to happen for a collision to be successful and lead to a reaction?

#### Back

-Correct orientation of molecules, -Equal to or greater than the activation energy,

### Card 3

#### Front

What are the graphs called which show the distribution of energies in a reaction?

### Card 4

#### Front

What are the two headings for the x-axis and y-axis?

### Card 5

#### Front

What does the area under the curve represent?

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