Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

AS levels Resurrection > C Unit 2.2 Rate of Reaction > Flashcards

C Unit 2.2 Rate of Reaction Flashcards

1
Q

How is the rate of reaction usually determined/calculated?

A

Measure the amount of reactant used up per unit time
Or
Measuring the amount of product made per unit time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the mains ways to increase rate/speed of a chemical reaction?
(A level 6 ways)

A
  1. Temperature
  2. SA or particle size
  3. Catalysts
  4. Concentrations
  5. Pressure
  6. Light
    (last 2 are the new ones)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the collision theory?

A
  • 2 reactant particles must collide successfully
  • To form new product
  • An effective collision
  • To increase rate of reaction, u must increase number of effective collisions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How may many collisions between reactant particles not form new product?

A
  • Reactant particles didn’t have sufficient energy
    to overcome activation energy
  • Particles collide in wrong orientation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

State how increase in concentration will affect the rate of reaction

A

Increasing the conc. of a solution, or the pressure of a gas, increases the rate of reaction. This is because more reactant particles present in the same volume ∴ there is an increase in number of collision per unit time. There will ∴ be a greater chance of successful collisions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

State how increase in temperature will affect the rate of reaction

A

Increasing temperature increases rate of reaction. This is because the reactant particles have greater KE at higher temps., so they move a lot faster. More of the particles have energy that is greater than the activation energy, so more successful collisions occur per unit time.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do they increase surface area of a solid reaction?

A

Cut up or ground into power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

State how increase in surface area will affect the rate of reaction

A
  • More of the reactant is exposed
  • Larger area for the reaction to take place
  • Increases rate of reaction
  • More chance of an effective collision
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is a catalyst?

A

Provides an alternate route with a lower activation energy
Without undergoing permanent change (can be re-used)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

State the 4 catalysts used for these 4 reactions:
- Haber process
- Catalytic convertors in cars
- Contact process
- Decomposition of hydrogen peroxide

A
  1. Iron
  2. Platinum
  3. Vanadium oxide
  4. Manganese oxide

All transition metals

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

State how increase in pressure will affect the rate of reaction

A
  • Decreases volume of gas
  • While maintaining number of particles
  • As they are closer together
  • More likely collisions
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

State how increase in light will affect the rate of reaction

A

E.g. chlorination of methane or photosynthesis
- Some reactions driven by light
- Light providing energy to either break bonds or produce more of a product
- It’s all the same tbh

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Do u know how to draw the changes of product if u change any of the factors within the reaction?

A

… yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How do u calculate the rate of a reaction?

A

Change in concentration/time
moldm-3/s = moldm-32-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How to calculate rate of reaction in terms of mass?

A

g/s = gs-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How to calculate rate of reaction in terms of volume?

A

cm3/s = cm3s-1

17
Q

How to establish relationship between reactant concentrations and rate?
(graph)

A

Well on a real:
At steepest - rate is fastest at start of reaction cuz concentration of reactants are the greatest (not much has been used up)
Line become less steep - rate slows down as reaction proceeds since the concentration of reactants decreases
Horizontal - rate becomes zero when reaction stops (reactants used up)

18
Q

Define activation energy Ea

A

Minimum energy required to start a reaction by the breaking of bonds

19
Q

Explain exothermic reaction

A

Reaction gives out heat and therefore the energy of the products is less than that of reactants - they have lost energy

20
Q

Explain endothermic reaction

A

Reaction takes in heat and therefore the energy of the products is higher than that of the reactants - they have gained energy

21
Q

Describe exothermic energy profile

A

Reactants = high
Curve (Ea) = high to low
Therefore △H = negative
Products = low

Ya gotta have known how to visualise this

22
Q

Describe endothermic energy profile

A

Reactants = low
Curve (Ea) = low to high
Therefore △H = positive
Products = high

23
Q

Describe reversible reaction energy profile

A

If one side is exo, the other side is endo
It’s a reversible reaction after all

Reactants is high (Vertical arrow with Ea forward)
Curve is high to low
Products is low (Vertical arrow on whole thing with Ea reverse)

24
Q

How to calculate enthalpy change of a reversible reaction energy profile?

A

△H = Eaf - Eab
(forward reaction - backward reaction)
Exothermic reaction △H = negative
Endothermic reaction △H = positive

25
Q

How does temperature affect the amount of energy the reactants have?

A
  1. Increasing temp = reactants more energy, move faster, ∴ more collisions, statistically more product, produced in a set time, ∴ rate of reaction increases
  2. More particles have activation energy
26
Q

Explain the Boltzmann distribution

A
  • It’s a graph.
  • Y-axis = number of particles with energy, E
  • X-axis = kinetic energy
  • Near the ends there’s a boundary:
    Ea aka the activation energy
    Only the number of particles represented under this section of the graph have sufficient energy to react
27
Q

Explain the difference of low temperature and high temperature in a Boltzmann distribution

A

At Low T:
- N° of molecules at it’s highest
- The activation energy is very small near the ends (the area)

At high T:
- The whole line looks like optimum pH level (if u know u know)
- Therefore technically n° not at its highest
- Activation energy is relatively bigger than of low T

28
Q

Describe the relation at high T within the Boltzmann distribution

A

As the temperature increases then the proportion of molecules with greater than activation energy also increase, therefore the rate increases

Broken english? wat??
and apparently 2 parts to the answer:
1. The increase in temperature, increases the energy (speed) of the molecules, therefore more collisions, therefore rate increases.
2. A greater proportion of molecules has greater than the required activation energy, therefore more product produced in the same time, therefore rate increases

29
Q

What are the 2 types of catalysts?

A
  • Homogeneous catalyst
  • Heterogeneous catalyst
30
Q

Explain homogeneous catalysts

A

The catalyst and reactants are in the same phase:
usually liquid mixtures or substances in solution

31
Q

An example of a homogenous catalyst?

A

Enzymes

32
Q

Benefits of enzymes?

A
  • Lower temp and pressure so lower costs
  • Operate in mild conditions so will not harm food or fabrics
  • Biodegradable - easy to dispose of
  • Often the products are pure with no side-products so no need to separate the unwanted products
33
Q

1 downside of enzymes?

A
  • Homogeneous catalyst = same phase
  • Therefore difficult to separate from the product
    (Though in some and in biological reactions, not necessary to remove em)
34
Q

Difference between enzymes and chemical catalysts?

A

Enzymes = react under extremely mild conditions (eg body temperature)
Chemical catalysts = often need severe conditions (high temp & pressure)

errr extremely effective at increasing the reaction rate - much more so than industrial catalysts

35
Q

Explain heterogeneous catalysts?

A

The catalysts and reactants are in different phases
(the trick = reactants are liquid/gas/aq but the catalyst is a solid soo voila)

  • Many are d-block transition metals
  • Gases absorbed on surface
  • React and then desorb from the surface
  • Larger surface area = better catalyst works
36
Q

Why do industries rely on catalysts?

A
  • Reduces costs
  • Lowers activation energy
  • Less energy required for molecules to react
  • Less electricity needed
  • LOWER COSTS
37
Q

How can colorimetry be used in studies of some reaction rates?

A

Wait…. I never know I was missing one more topic D:

38
Q

I’d like to hope that’s it. No way this topic gets any complicated

A

…. right?

39
Q

He was dumbfounded

A

Sadly

AS levels Resurrection (22 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions