Chemical equilibria
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What is a reversible reaction?
A reaction where reactants form products and products can turn back into reactants
What does a reversible arrow indicate?
Both forward and backward reactions can occur
What happens at the start of a reaction?
Only reactants are present
How does the forward reaction rate change over time?
It decreases as reactants are used up
How does the backward reaction rate change over time?
It increases as products are formed
What is dynamic equilibrium?
When the forward and backward reaction rates are equal and concentrations remain constant
What does dynamic mean?
Both forward and backward reactions are occurring
What does equilibrium mean?
Concentrations remain constant
What condition is needed for dynamic equilibrium?
A closed system
How is dynamic equilibirium reached?
Forward reaction slows, reverse speeds up until rates are equal
What does the position of equilibrium refer to?
Relative amounts of reactants and products
What does shifting right mean?
More products than reactants
What does shifting left mean?
More reactants than products
What can reversible reactions be problematic?
Products may turn back into reactants
What does Le chatelier’s principle state?
Equilibrium shifts to oppose a change
What does a shift to the right?
Increases product concentration
What does a shift to the left do?
Increases reactant concentration
What type of equilibria does the shifting apply to?
Homogeneous equilibria
What happens if concentration of reactant increases?
Shifts right to oppose increase so more products
What happens if concentration of reactant decreases?
Shifts to the left to oppose decrease and so fewer products and more reactant
When do pressure changes affect equlibirum?
Only in reactions involving gases
What happens when pressure increases?
Shifts to the side with fewer moles of gas
What happens when pressure decreases?
Shifts to side with more moles of gas
What if moles are equal on both sides?
No effect on equilibrium