Module 5: Equilibrium and Acid Reactions Flashcards
What is chemical equilibrium?
the reverse reaction is converting products into reactants as fast as products are formed in the forward direction. At this point, concentration no longer changes.
What is static equilibrium?
when all of the reactant particles remain as reactants and all of the products remain as products.
What is dynamic equilibrium?
When there is a constant exchange from reactants to products (or vice versa).
When should an arrow be used and when should the equilibrium symbol be used?
The arrow should be used to represent irreversible chemical reactions and the equilibrium symbol should be used to represent reversible chemical reactions
Important features of equilibrium systems:
- Equilibrium is only achieved when the system is closed (matter will neither be lost or gained).
- Chemical equilibria are dynamic (the rate of the forward reaction = the rate of the reverse direction).
- Constant macroscopic properties are an indicator of dynamic equilibrium (includes colour, pressure, volume, electrical conductivity).
Potassium dichromate and potassium chromate: Explanation
Concentration was changed
With the addition of HCl: According to Le Chat. The reaction will resist the change by decreasing the concentration of H+ ions. The reaction will favour the reverse directions and shift to the left. It adds H+ ions and it becomes orange.
With the addition of NaOH: According to Le Chat. The reaction will resist the change by increasing the concentration. It removes H+ ions due to the creation of more H20. The reaction will favour the forward directions and shift to the right.
Nitrous Oxide and dinitrogen tetroxide: Explanation
NO2 = coloured and N2O4 = colourless
Cold flask= colourless gas and room temp= brown gas
According to Le chat. The increase in heat shifts the reaction to the right which will increase colourless gas. It favours the forward reaction.
Nitrous Oxide and dinitrogen tetroxide: Explanation for pressure
When the syringe was depressed= lighter colour and expanded= more coloured
According to Le Chat. the reaction shifts to the right to increase the pressure and consequently decrease the volume. It favours the forward reaction.
Nitrous Oxide and dinitrogen tetroxide: Explanation for temperature
NO2 = coloured and N2O4 = colourless
Cold flask= colourless gas and room temp= brown gas
According to Le chat. The increase in heat shifts the reaction to the right which will increase colourless gas. It favours the forward reaction.
Burning Steel Wool: Explanation
This reaction is irreversible as the wool can not be unburned this means there is no equilibrium occurring and thus the equations should only be represented with an arrow.
What is the difference between entropy and enthalpy?
Entropy= chaos Enthalpy= heat in reactants and products
G equation and spontaneous/ equilibrium
When G < 0 The reaction is SPONTANEOUS
When G > 0 the REVERSE reaction will be spontaneous (The forward reaction is not spontaneous).
When G = 0 the reaction is in EQUILIBRIUM.
Combustion: Gibbs Free energy
As the Gibbs free energy for both combustion and respiration is <0 these reactions are considered spontaneous. They are NOT in equilibrium and will favour the forward reaction.
Photosynthesis: Gibbs Free energy
Photosynthesis requires a considerable amount of energy to proceed and therefore has a Gibbs free energy > 0. This reaction is not spontaneous (although the reverse reaction – respiration, is).
It is NOT in equilibrium and will favour the reverse reaction (respiration).
Investigate the relationship between collision theory and reaction rate in order to analyse chemical equilibrium reactions
Collision theory states that, for a reaction to occur, the particles must collide with sufficient energy to break the bonds and have the appropriate orientation to allow the new bonds to form. This theory can also be used to understand why some reactions are reversible and others are not. You will recall that the amount of energy required to break the bonds of the reactants is known as the activation energy. In a reaction, the activation energy of both the forward and reverse reaction must be low enough that sufficient particles will have enough energy for a successful collision.
