10 Rates and Equilibrium Flashcards
What is collision theory?
For a reaction to occur:
- Particles must collide
- Must have sufficient energy
- With the correct orientation
What happens if to collisions if surface area is increased?
More particles on the surface and able to collide with other particles
More frequent collisions and therefore more frequent successful collisions
What is the effect of increasing temperature on rate?
- Particles moving faster and have more energy so collide more frequently. Higher number of total collisions so more frequent
- Higher proportion of molecules have or exceed the activation energy. Higher proportion of collisions are successful (main reason)
What is the effect of concentration on collisions?
More particles in the same volume
More frequent successful collisions
What is a catalyst and how does it work?
Increases the rate of reaction without being used up
Provides alternative reaction pathway with a lower activation energy. More particles with E >/ Ea
What is a homogenous catalyst?
Catalyst in the same physical state as the reactants
Catalyst reacts to form an intermediate, then breaks down to give products and the regenerated catalyst
What is an auto-catalyst?
One of the products used as a catalyst
eg 2 negative ions repelling
addition of positive catalyst
What is a heterogeneous catalyst?
The catalyst is in a different physical state to the reactants
Reactants adsorb onto surface of catalyst, react then desorb
Why are catalyst important (what does reducing the activation energy of the reaction reduce)?
Reduces:
- Temperature needed
- Energy requirements
- Electricity or fossil fuels used
- Costs (increase profitability)
- Carbon dioxide emissions
- Unused reactant, waste products
What is the Boltzmann distribution?
Distribution of energy across all particles in a sample at a particular temperature
What does the area under the curve represent?
Total number of particles
Only particles in blue shaded area have enough energy to collide successfully
What happens to the curve at a higher temperature?
Rate of reaction increases:
The peak is lower and shifted to the right (total area same)
Greater proportion of molecules can overcome activation energy
What happens to the curve with the addition of a catalyst?
Rate of reaction increases:
Energy of particles is unchanged
Activation energy reduced so greater proportion exceeds the new lower activation energy
What is dynamic equilibrium?
State of balance that a reaction can exist in, rate of forwards reaction is equal to the rate of the reverse reaction, in a closed system
Concentrations of reactants and products no longer change
What effect do catalysts have on reversible reactions?
Increases rate of the forward reaction by the same amount as it increases the reverse reaction
