Topic 10 Equilibrium 1 Flashcards
What is the definition of a reversible reaction?
A chemical reaction where the reactants form products (forward reaction), which in turn form reactants (backward reaction).
Is the forward reaction exo- or endo-thermic? Backward reaction?
The forward and backward reactions can be either exothermic or endothermic. This will be stated in the question
What is the definition of dynamic equilibrium?
A state of balance between continuing processes. In a reversible reaction it is where the forward and backward reactions are occurring at the same rate.
What is the definition of a closed system?
A system in which no reactants or products can enter or escape but where energy transfer takes place.
What is Le Chatelier’s Principle?
The equilibrium will ‘shift’ to oppose any external change. (e.g. if the temperature is increased the equilibrium will try to decrease temperature - favour exothermic reaction).
What are the equilibrium constants?
K꜀ and Kₚ
What do the [] (square brackets) mean in the K꜀ equation?
Concentration of the substance. e.g. [H₂] is the concentration of H₂.
What is the K꜀ equation?
[Products] / [Reactants]
e.g. A + 2B ⇌ 3C + D
[C]³+[D] / [A]+[B]²
What are the units for K꜀?
mol dm⁻³ (This is for each molecule in the K꜀ equation. you will need to work out the final units)
e.g. A + 2B ⇌ 3C + D [C]³+[D] / [A]+[B]² (mol dm⁻³)³+(mol dm⁻³) / (mol dm⁻³)+(mol dm⁻³)² (mol dm⁻³)⁴ / (mol dm⁻³)³ (mol dm⁻³) / 1 = mol dm⁻³
What affect does changing the temperature have the equilibrium?
Increase: Shifts left if forward reaction is exothermic, shifts right if forward reaction is endothermic.
Decrease: Shifts right if forward reaction is exothermic, shifts left if forward reaction is endothermic.
What affect does changing the pressure have on the equilibrium?
Increase: Shifts left if there are more products, shifts right if there are more reactants, no change if there are equal number of molecules on each side.
Decrease: Shifts right if there are more products, shifts left if there are more reactants, no change if there are equal number of molecules on each side.
What affect will removing some of a substance have on the equilibrium?
This depends on what substance is removed.
e.g. In A + 2B ⇌ 3C + D, if D is removed, the equilibrium will shift to the right to replace it. If B is removed, the equilibrium will shift to the left to replace it. If any substance is continually removed, the equilibrium will continually shift to replace the substance until an irreversible reaction is formed.
