Major Ideas: Rates And Equilibrium Flashcards
Equation for rxn rate
Change in quantity
_________________
Time interval
How can the rate of rxn be determined?
By measuring the change in the amount of one of the reactants or one of the products in a given time interval
What dis the slope of a quantity vs. time graph tells us
Rxn rate at particular time (gradient)
3 conditions of collision theory
- particles must collide
- must collide with sufficient energy to react
- must collide at the correct orientation
What is activation energy
Minimum energy required by colliding particles for a reaction to occur
What is the transition state (a.k.a the activated complex)? (3points)
- highest potential energy state for the reacting system
- corresponds to some stage in rxn at which bond breaking and forming occur
- unstable (only temporary existence)
What is the activation energy of a FORWARD rxn?
Energy difference between the transition state and reactants
What is the change in enthalpy (^H)
Difference of potential energy (enthalpy) between reactants and products
For an EXOTHERMIC rxn:
- relationship between products and reactants (energy)
- ^H value
- surrounding temperature (why?)
- products have LESS potential energy than reactants
- ^H is negative
- temperature of surrounding increase (releases heat)
For an ENDOTHERMIC rxn:
- relationship between products and reactants (energy)
- ^H value
- surrounding temperature (why?)
- products have more potential energy than reactants
- ^H is positive (E.products-E.reactants)
- temperature of surroundings decrease (absorb heat)
Factors that affect rxn rate:
1. Nature of reactants
Breaking covalent bonds requires more energy, therefore resulting in a slower rate than reactions just involving collision
Factors that affect rxn rate:
2. Concentration
Higher concentration = more particles = more collisions = higher rate of rxn
Factors that affect rxn rate:
3. Pressure
Higher pressure = less ‘space’ = more collisions = higher rate of rxn
Factors that affect rxn rate:
4. Surface area
Bigger surface area = more particles exposed = moe collisions = higher rxn rate
Factors that affect rxn rate:
5. Temperature
Increase temperature = increase Ek of particles = move faster = more collisions = higher rate of rxn
Factors that affect rxn rate:
6. Catalyst
Provides alternative pathway for rxn = decreases activation energy = higher rate of rxn
2 conditions for a system to be at equilibrium
- conc. of reactants and products present remain constant at all times
- rate of both forward and reverse rxns are equal
What is an equilibrium constant?
- constant value representing rxn at particular temp.
What I’d Le Châtelier’s principle?
A system at equilibrium that is subjected to change will adjust to re-establish equilibrium in such a way as to partially counteract the imposed change
Effect of changes on equilibrium:
1. Concentration
Favour direction of equation that will oppose change
- decrease = favour side that produces more
- increase = favour side that ‘uses up’
Effect of changes on equilibrium:
2. Pressure
Increase = favour side that has less particles Decrease = favour side with more particles
Effect of changes on equilibrium:
3. Temperature
- increase: favour endothermic rxn
- decrease: favour exothermic rxn
Effect of changes on equilibrium:
4. Volume
Increase volume = decrease pressure
Decrease volume = increase pressure
Effect of changes on equilibrium:
5. Catalyst
No effect on position in equilibrium but allows system to reach equilibrium quicker
