Kinetics & Equilibria Flashcards
Define dynamic equilibrium and state two conditions.
The rates of the forwards and reverse reactions are equal.
- The concentrations of reactants and products are constant
- The reaction is in a closed system
What is the collision theory?
That particles must collide with correct orientation and sufficient energy for a reaction to take place.
How does increasing the temperature affect the rate of reaction?
Increasing the temperature causes:
The distribution to shift the the right.
The average kinetic energy of the molecules increases.
A greater proportion of molecules have energy >= the activation energy.
A greater proportion of successful collisions result in reaction.
Define activation energy.
The minimum energy required for a reaction to start.
How does a catalyst speed up the rate of a reaction?
A catalyst provides an alternative reaction route of lower activation energy (forms an activated complex).
A greater proportion of molecules have energy >= the activation energy.
Describe how colorimetry can be used to measure the rate of reaction.
- Measure the absorbance/ transmittance of light
2. Use a calibration curve to convert absorb/trans into concentration
What is Le Chatelier’s Principle?
If a system in dynamic equilibrium is disturbed, it responds to oppose the change.
What effect does increasing the following have on the equilibrium position?
a) Temperature
b) Pressure
c) Concentration
a) Exothermic reaction - shifts eqm to the left (endothermic side)
Endothermic reaction - shifts eqm to the right (endothermic side)
b) Shifts eqm to the side with the fewer number of moles
c) increasing reactants shifts eqm to the right
How does a heterogeneous catalyst work?
- Adsorption: reactant adsorbed onto catalyst surface (active sites)
- Reaction: rate of reaction is increased as adsorption weakens bonds within reactants (lowers Ea) & changes orientation
- Desorption: products formed
