7.1 Equilibrium Systems Flashcards
Do all chemical reactions proceed to completion?
No
Define Chemical Equilibrium
State of reaction where reactants and products have reached constant concentrations in a closed system
What’s a forward reaction
Left to right (reactants to products)
What’s a reverse reaction
Right to left (products to reactants)
Define closed system
A system where matter cannot be transferred between systems and surroundings, but energy can
How is bromine an example of a physical equilibrium (also applies to water)
Bromine has volatile energy to evaporate, and its vapor collides with its liquid to become liquid bromine. The rate of condensation is equal to the rate of evaporation, making it an equilibrium with no net change in liquid and gas present.
How is decomposition of HI a chemical equilibrium
As [HI] decreases the reverse reaction rate increases and eventually both rates become equal and their concentrations become constant.
Are all chemical equilibriums dynamic?
Yes
What is the equilibrium position
The relative concentrations of reactants and products at equilibrium
In equilibrium, do the concentrations of reactants ever reach 0?
No
What are reversible reactions
Reactions that can proceed in both forward and reverse directions
Is the equilibrium position the same regardless of the direction it was achieved in?
Yes
What are the 5 characteristics of an equilibrium
1) equilibrium is dynamic
2) it is in a closed system
3) concentrations of all reactants and products remain constant at equilibrium
4) macroscopic properties do not change
5) can be achieved in either direction
Explain how NO2 <-> N2O4 is an example of a reaction not proceeding to completion
NO2 is a dark gas whilst N2O4 is colorless. In a closed system the vial gets lighter but never colorless even when it reaches equilibrium. The reactant never ran out, so it does not proceed to completion.
In dynamic equilibrium, the rate of the forward reaction is _____ to the rate of the reverse reaction
Equal
What does a dashed line on a chemical reaction graph indicate
Equilibrium was reached and all concentrations will remain constant
When concentrations of reactants and products are not changing, is the reaction always at equilibrium? Use ammonia synthesis to explain (N2 + 3H2 <-> 2NH3)
No. The reactants of ammonia synthesis have very high bond energies making them unreactive. A catalyst is required such as iron to drive the reaction to equilibrium.
In a Pepsi bottle, what happens if you open it?
There is a decrease in pressure so the reaction shifts and a new equilibrium is established
In a Pepsi bottle, where do the bubbles come from? How is it dynamic?
Carbonic acid decomposing into CO2 and water. Both forward reactions and reverse occur at same time (synthesizing H2CO3 and decomposition)
