Chemistry C3 4.7 Altering conditions.

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How can changing the pressure affect reversible reactions involving gases at equilibrium?
Increasing the pressure favours the reaction with the smaller number of molecules of gas formed; decreasing the pressure favours the reaction with the larger number of molecules of gas formed.
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How can changing the temperature at which we carry out a reversible reaction change the amount of products formed at equilibrium?
Increasing the temperature favours the endothermic reaction; decreasing the temperature favours the exothermic reaction.
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What happens if we change the conditions of a system at equilibrium?
The position of equilibrium shifts as if to try to cancel out the change.
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For reversible reactions that have different numbers of molecules of gases on one side of the equation than the other, what effect does changing the pressure have?
Changing the pressure will affect the position of equilibrium, e.g. if the pressure is increased the position of equilibrium will shift to try to reduce the pressure (favour the reaction that produces fewer molecules of gas).
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What effect does pressure have if the forward reaction produces more molecules of gas?
An increase in pressure decreases the amount of products formed; a decrease in pressure increases the amount of produces formed.
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What effect does pressure have if the forward reaction produces fewer molecules of gas?
An increase in pressure increases the amount of products formed; a decrease in pressure decreases the amount of products formed.
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In the reversible reaction 2NO_2(g) = N_2O_2(g) there are more gaseous reactant molecules than gaseous product molecules, what happens if pressure is increased?
Increasing the pressure will increase the amount of N_2O_4 (product) in the mixture at equilibrium.
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What are reversible reactions in either direction?
Reversible reactions are exothermic in one direction and endothermic in the other direction.
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What happens to a reversible reaction if the temperature is increased?
Increasing the temperature favours the reaction in the endothermic reaction, the equilibrium shifts as if to lower the temperature by taking in energy.
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What does decreasing the temperature favour?
The exothermic reaction.
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How does temperature effect a reversible reaction if the forward reaction is exothermic?
An increase in temperature decreases the amount of products formed; a decrease in temperature increases the amount of products formed.
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How does temperature effect a reversible reaction if the forward reaction is endothermic?
A decrease in temperature increases the amount of products formed; a decrease in temperature decreases the amount of products formed.
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How does an increasing the temperature affect the reversible reaction 2NO_2(g) = N_2O_4(g)?
The forward reaction is exothermic so increasing the temperature will produce more NO_2 (reactant) in the mixture of equilibrium.
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For the reaction 2SO_2(g) + O_2(g) = 2SO_3(g) what change in pressure will increase the amount of SO_3 in the equilibrium mixture?
An increase in pressure.
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The reaction 2SO_2(g) + O_2(g) = 2SO_3(g) is exothermic in the forward direction. What change in temperature will increase the amount of SO_3 at equilibrium?
A decrease in temperature.
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**YOU SHOULD BE ABLE TO DESCRIBE THE EFFECT OF CHANGING CONDITIONS OF TEMPERATURE AND PRESSURE ON A GIVEN REVERSIBLE REACTION**
**EVEN THOUGH THERE ARE TWO REACTIONS IN A REVERSIBLE REACTION, BY CONVENTION WHEN WE WRITE AN EQUATION FOR ANY REACTION WE CALL THE SUBSTANCES ON THE LEFT-HAND SIDE THE REACTANTS AND THOSE ON THE RIGHT-HAND SIDE THE PRODUCTS**
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**IN THE EXAM YOU WILL BE TOLD WHICH DIRECTION THE REACTION IS EXOTHERMIC OR ENDOTHERMIC**
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Other cards in this set

Card 2

Front

How can changing the temperature at which we carry out a reversible reaction change the amount of products formed at equilibrium?

Back

Increasing the temperature favours the endothermic reaction; decreasing the temperature favours the exothermic reaction.

Card 3

Front

What happens if we change the conditions of a system at equilibrium?

Back

Preview of the front of card 3

Card 4

Front

For reversible reactions that have different numbers of molecules of gases on one side of the equation than the other, what effect does changing the pressure have?

Back

Preview of the front of card 4

Card 5

Front

What effect does pressure have if the forward reaction produces more molecules of gas?

Back

Preview of the front of card 5
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