Unit 2 section 1&2 chemistry

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What is enthalpy change?
The heat energy transferred in a reaction of constant pressure
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What is the enthalpy change of an exothermic reaction and why?
Negative enthalpy change or negative change in energy because energy is given out in an exothermic reaction
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Are bonds broken or created in an exothermic reaction?
Bonds are broken, so energy is given out which means negative enthalpy change
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what is the equation for enthalpy change?
total energy absorbed - total energy released (found by using bond energy)
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What are the 3 types of enthalpy change?
Reaction, formation and combustion
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What two things do you need to know to measure enthalpy change in a lab?
Number of moles of reactant and change in temp
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What is Hess's Law?
The total enthalpy change of a reaction is the same no matter which path you take
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what is the activation energy?
The minimum amount of energy needed for the particles to start reacting
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What is the maxwell- Boltzmann distribution?
Graph of no of molecules (Y) and kinetic energy (x) with a curve shape
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What happens when you increase the temperature?
The peak is lower and more atoms are in the activation energy zone
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What happens when you increase the concentration?
peak is higher on top of the activation energy and the top
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What does a catalyst do to the graph?
Moves the activation energy to the left because its lowered
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why dont all collisions end up in a reaction?
have to be correctly orientated and have enough kinetic energy
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What is the dynamic equilibrium?
When the forward and backward reaction occur at the same rate in a closed system?
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What 3 things alter equilibrium?
Concentration, temperature, pressure
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What happens if the equilibrium is pushed left?
More reactants
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What does a catalyst do to the position of the equilibrium?
Nothing
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What happens if you increase the concentration of reactants?
equilibrium is pushed towards the products giving more products
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What happens to the equilibrium when you increase the pressure
shifts to the side with fewer gas molecules
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what happens when you increase the temperature?
Favours endothermic side as it absorbs the added head
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What two things are added together to make ethanol and what conditions?
ethene + h20(steam), 60-70ATM, 300 degress c and phosphoric acid catalyst
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Why do companies pick a high temp on this reaction?
Low temp favours the reaction, but slows down the reaction rate so its better to increase it
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Why do companies pick a lower pressure?
high pressure favours the ethanol side, but more expensive because better equipment is needed
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Other cards in this set

Card 2

Front

What is the enthalpy change of an exothermic reaction and why?

Back

Negative enthalpy change or negative change in energy because energy is given out in an exothermic reaction

Card 3

Front

Are bonds broken or created in an exothermic reaction?

Back

Preview of the front of card 3

Card 4

Front

what is the equation for enthalpy change?

Back

Preview of the front of card 4

Card 5

Front

What are the 3 types of enthalpy change?

Back

Preview of the front of card 5
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