C Unit 2.2 Rate of Reaction Revamp Flashcards
4 ways to increase the rate/speed of a chemical reaction?
- Temperature
- SA or particle size
- Catalysts
- Concentration
2 new ways to increase the rate/speed of a chemical reaction?
- Pressure
- Light
Collisionally speaking… how is the rate of reaction rlly being increased?
(2-way)
- Due to the increase of
- the n° of effective collisions
How can an increase in conc. affect the rate of reaction?
(4-way)
- More reactant particles present
- in same volume
- ∴ increase in n° of collisions
- as greater chance of successful collisions
How can increase in temp. affect the rate of reaction?
(4-way)
- Reactant ptcls have greater KE
- Move faster
- More ptcls greater energy than activation energy
- More successful collisions
How can increase in surface area affect rate of reaction?
(4-way)
- More of the reactant exposed
- Larger area for reaction to take place
- More chance of an effective collision
- Greater chance of successful collisions
Explain how pressure can affect rate of reaction?
(2-way + 2-way)
- Higher pressure = decrease of vol. of gas
- while maintaining n° of ptcls
- Ptcls more closer together
- more likely collisions
How can light affect rate of reaction?
(3-way)
- Some rxns driven by light
- e.g. chlorination of methane (uv light)
- photosynthesis
How to calculate rate of reaction?
(eqn)
Rate = change in concentration/time
… simple dimple
Explain the rate at the steepest part of the graph?
(3-way)
- Fastest
- Conc. of reactants are at its greatest
- Not much has been used up
Explain the rate at less steep part of the graph?
(2-way)
- Rate slows down as rxn proceeds
- Conc. of reactants decreases
At what point of graph is when the rate becomes zero and why?
(2-way)
- Horizontal typa line….
- Reaction stops as all reactants used up
Relationship between concentration and “rate constant” for zero order?
Not proportional,
rate no change if conc. change
Relationship between concentration and “rate constant” for first order?
Directly proportional,
Rate 2x if Conc. 2x
Relation between concentration and “rate constant” for second order?
Direct square law,
Rate is “n”2 if Conc. “n”x
Define activation energy (EA)?
(2-way)
- Min. energy required to start a reaction
- by the breaking of bonds
Explain exothermic reaction. (3-way)
Draw it’s profile.
- Rxn gives out heat
- Energy of products less than reactants
- Lost energy
Stage is yours
Explain Endothermic reaction. (3-way)
Draw it’s profile.
- Rxn takes in heat
- Energy of products more than reactants
- Gained energy
Case closure?
Draw reversible reaction energy profile
All yours.
How to find enthalpy change of reversible reaction from its energy profile?
ΔH = EAf - EAb
State the ΔH of an exo & endo reaction?
- Exo rxn ΔH = Negative
- Endo rxn ΔH = Positive
Difference for the energy profile if u added a catalyst?
EA “hill” will be smaller
Explain how increasing temp. affects amount of energy reactants have?
(4-way)
- Reactants have more energy + move faster
- More collisions, statistically more product
- Rate of rxn increases
- More particles have EA
Draw a typical Boltzmann distribution +
3 labels…
Stages’ yours
- LHS = n° of ptcls not have enough energy to react
- RHS = n° of ptcls have enough energy to react
- Ptcls w/ energy higher than EA will react
Explain the EA part in the Boltzmann distribution?
Pretty much how much ptcls have high energy.
Explain Boltzmann distribution for low temperatures?
(4-way)
- High n° of molecules “initially”
- More molecules of low energy
- Less molecules have higher energy than EA/sub>
- Rxn rates = slower (fewer molecules react)
Explain Boltzmann distribution for higher temperatures?
(4-way)
- n° of molecules distribution shifts to right
- More molecules have higher energies
- More molecules have energies ≥ EA
- Rxn rates = faster (more molecules react)
How does a catalyst alter the rate of a chemical reaction?
(2-way)
- Provides alternate route
- w/ lower EA
Draw Boltzmann distribution graph but catalyst is included
Stage is yours y’all
What are the 2 types of catalysts?
- Homogenous catalyst
- Heterogeneous catalyst
Define homogenous catalyst?
When catalyst + reactant = same state
(e.g. enzymes)
Define heterogenous catalyst?
When catalyst + reactant = different state
(e.g. transition metals B|)
Benefits of enzymes
(Pick and roll… wat)
- Lower temp + pressure = lower costs
- Mild conditions, less harmful for products + safe
- Biodegradable
- Often pure products, no excess products or summin
Drawback of enzymes??
Same phase ∴ difficult to separate…. although some may not need the removal
Why do industries rely on catalysts?
To reduce costs B|
What are the 4 main ways of measuring the rate of reaction?
- Evolution of a gas
- Change in colour
- Measuring pH
- Sampling
Explain “evolution of a gas”?
(Measuring rate of reaction)
Aye it speaks for itself but ig it’s its property
Explain “change in colour”?
(Measuring rate of reaction)
Intensity of colour relates to its concentration
Explain “measuring pH”?
(Measuring rate of reaction)
Titration ig?
Explain “sampling”?
(Measuring rate of reaction)
(2 things)
- Samples removed at various times
- Analysed for a particular reagent?
What 3 things go under “evolution of a gas”?
(Measuring rate of reaction)
- Change in gas volume
- Change in mass (technically… ish… meh)
- Change in gas pressure
What goes under “sampling”?
(Measuring rate of reaction)
(3 things)
- Precipitation reactions
- How long it takes for it to form/change colour
- Solid needs to be produced
Explain how the colorimetry works?
(Check-up… idk)
- Colour change… conc. of substance changing colour being monitored
- Colorimeter has a light source w/ filters
- which selects colour of light absorbed by sample
- Light passes onto detector
- Photocell gains info, connected to pc
- Electrical signal yadda yadda, known conc. gain
Eyes on the prize
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