Chapter 5A - Equilibrium Reactions Flashcards
Why can some reactions not reach completion?
- products collide and react to reform the reactants
What is an irreversible reaction?
- reaction goes to completion
e.g. fuel combustion
In what ways is an irreversible reaction indicated?
- arrow in equation points in one direction
- concentration of reactants in a concentration vs time graph reaches zero.
Is this a reversible or irreversible reaction?
Irreversible
What is a reversible reaction?
- reaction doesn’t go to completion
- reaction can precede in the forwards and backwards direction if conditions favourable
- closed systems only
In what ways is a reversible reaction indicated?
- arrow points in both directions
- concentration of reactants in a concentration time graph is greater than 0 and constant once equilibrium established.
Is this reaction reversible or irreversible?
Reversable
Define rate of reaction
How much product is formed over a given amount of time
Define extent of reaction
Proportion of reactants that have been converted into products (yield)
Is the extent of reaction same for all reactions?
- Different conditions have different extents
- Does not indicate reaction rate
How can extent be determined experimentally?
- measuring reactants/products at equilibrium
- using concentration fraction to calculate equilibrium constant (K) where magnitude of K indicates extent
What are the conditions for dynamic equilibrium?
- reactant/product amount is constant
- net concentrations of reactants/products don’t change over time
- temperature of system is constant
- pressure of system is constant
What is dynamic equilibrium?
Rate of forwards reaction = rate of backwards reaction
* Reactions have not ceased, occurring simultaneouslu
What are the considerations regarding Dynamic Equilibrium?
- Equilibrium can only be reached in a closed system if reaction involves gas
- Equilibrium can be reached in both chemical reactions and changes of state
How can equilibrium reactions be represented?
- concentration-time graphs
- rate-time graphs
What are concentration-time graphs?
- displays concentration of reactants and products over time
- concentration changes in ratio
What are rate - time graphs?
- displays the rate for both the forwards and reverse reactions
What happens to the rate of forwards reaction before a system reaches equilibrium?
- Rate decreases overtime
- Decreased amount of reactants
What happens to the rate of the reverse reaction before a system reaches equilibrium?
- Rate intially increases
- Increased presence of products
Define Yield
Amount of product obtained in reaction
