10: Equilibrium I Flashcards
What is a reversible reaction
A reaction where the products can react together to reform the original reactants
What are the aspects of dynamic equilibrium
- The reactants and products are dynamic (constantly moving)
- The rate of the forward reaction is the same as the rate of the backwards reaction
- Closed system
- Concentrations of reactants and products are constant
What is a closed system
A reaction where none of the reactants or products escape from the reaction mixture (energy isn’t lost)
What is an open system
A reaction where matter and energy can be lost to the surroundings
What is the position of equilibrium
- Refers to the relative amounts of products and reactants in an equilibrium mixture
- When POE shifts to the left, concentration of reactants increases
- When POE shifts to the right, concentration of products increases
What is Le Chatelier’s Principle
If a change is made to a system in dynamic equilibrium, the position of equilibrium moves to counteract this change
What are the effects of change in concentration of the reactants on equilibrium
- If concentration of reactants increases, POE shifts to the side with a lower concentration (right)
- If concentration of reactants decreases, POE shifts to the side with a lower concentration (left)
What are the effects of change in concentration of the products on equilibrium
- If concentration of products increases, POE shifts to the side with a lower concentration (left)
- If concentration of products decreases, POE shifts to the side with a lower concentration (right)
What happens when water is added to the reaction mixture
Nothing, as there is no concentration change as water dilutes all ions equally
How do changes in pressure affect the equilibrium
- Increase in pressure, POE shifts to the side that produces the smaller number of molecules of gas
- Decrease in pressure, POE shifts to the side that produces the larger number of molecules of gas
How do changes in temperature of exothermic reactions affect the equilibrium
- Increase in temperature, POE moves in the endothermic direction (backwards)
- Decrease in temperature, POE moves in the exothermic direction (forwards)
How does increasing the temperature of the Haber Process affects the yield of products
The forwards reaction is exothermic, so an increase in temperature may increase the rate of reaction, but also causes the POE to shift to the left, which decreases the overall yield of ammonia
How does increasing the pressure of the Haber Process affect the yield of products
An increase of pressure will cause the POE to shift to the right, as this is the side with less molecules of gas, which will increase the yield of ammonia
Why does temperature sometimes have to be compromised in industrial processes (e.g. Haber Process)
- Haber Process uses a temperature of 450 degrees C as this produces an acceptable yield of ammonia (35%) in an acceptable time frame
- Higher temperatures aren’t used because it would produce lower yields combined with increased costs to achieve high temperature
- Lower temperature isn’t used as the rate is too slow despite increased yields of ammonia
Why does pressure sometimes have to be compromised in industrial processes (e.g. Haber Process)
- A pressure of 200 atm is used which produces an acceptable yield of ammonia (35%)
- Increasing the pressure doesn’t increase the yield by a great enough amount to ignore the financial and energy costs, and the safety of the process
How to deduce equilibrium expression
