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Chemistry A-Level > Kinetics > Flashcards

Kinetics Flashcards

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1
Q

What are the 5 main factors affecting rate of reaction?

A
  • Conc.
  • Pressure.
  • Temp.
  • SA.
  • Catalyst.
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2
Q

Define rate of reaction.

A
  • Change in conc of a reactant or product in a given period of time.
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3
Q

Define activation energy.

A
  • Minimum amount of energy which reacting particles require for successful collision.
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4
Q

How does conc affect ror?

A
  • Conc increase.
  • More particles of reactant present.
  • More successful collisions in given period of time.
  • ∴ ror increases.
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5
Q

How does pressure affect ror?

A
  • Pressure increase in gaseous reaction system.
  • Particles forced closer together.
  • Leads to more successful collisions in given period of time.
  • ∴ ror increases.
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6
Q

How does temp affect ror?

A
  • Temp increase, particles gain energy + move faster.
  • More frequent successful collisions in given period of time.
  • ∴ ror increases.
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7
Q

How does SA affect ror?

A
  • Increasing SA increases exposed surface of reactants.
  • Increase in number of successful collisions in given period of time.
  • ∴ ror increases.
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8
Q

How do catalysts affect ror?

A
  • Catalyst increase ror wo/ being used up.
  • Provide alternative reaction pathway of lower activation energy.
  • More successful collisions in given period of time.
  • ∴ ror increases.
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9
Q

Why are catalysts important in industrial processes?

A
  • Speed up reactions ∴ reduce costs.
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10
Q

What type of graph can be used to show exothermic and endothermic reactions?

A
  • Enthalpy profile diagrams or reaction profile diagrams.
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11
Q

Draw an enthalpy diagram for an exothermic reaction.

A

…

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12
Q

Draw an enthalpy diagram for an endothermic reaction.

A

…

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13
Q

What is a Maxwell-Boltzmann distibution?

A
  • Plot of number of gaseous molecules against energy at fixed temp.
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14
Q

What type of molecules is a Maxwell-Boltzmann distribution used for?

A
  • Gaseous molecules.
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15
Q

What is a Maxwell-Boltzmann distribution also called?

A
  • Molecular energy distribution graph.
  • Distribution of molecular energies.
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16
Q

What is important about the temp in a Maxwell-Boltzmann distribution?

A
  • Constant.
17
Q

What does a Maxwell-Boltzmann distribution look like at a constant temp?

A
  • Roughly normal distribution which is asymptotic to the horizontal axis.
18
Q

What are the 5 main points from a Maxwell-Boltzmann distribution at constant temp?

A
  • 0 molecules have 0 energy ∴ starts at origin.
  • Area under graph = total no. molecules present.
  • Peak is most probable energy of molecules (Emp).
  • Most molecules have moderate energy in middle of graph.
  • Very few molecules have high energy but asymptote as no upper limit to the energy of particles.
19
Q

How is activation energy represented on a Maxwell-Boltzmann distribution?

A
  • Ea.
20
Q

What are on the x and y axis of a Maxwell-Boltzmann distribution?

A
  • x –> Energy.
  • y –> No. molecules.
21
Q

Using a M-B distribution how does increasing a catalyst increase ror?

A
  • More area above activation energy.
  • ∴ more molecules w sufficient energy for successful collisions.
22
Q

Does using a catalyst affect the shape of a M-B distribution?

A
  • No bc total no. molecules + temp are same.
23
Q

Does increasing temp affect the shape of a M-B distribution?

A
  • Yes because increase in energy of reactants.
24
Q

What 4 things should you note when sketching a distribution for the same sample of gas at a lower or higher temp?

A
  • Lower –> distributions moved to left + peak is higher.
  • Higher –> moved to right + lower peak.
  • Graphs should only cross once.
  • Curves always start at origin + are asymptotic.
25
Q

Using a M-B distribution how does increasing temp affect ror?

A
  • Higher temp, more area under graph at Ea
  • ∴ more reactant molecules to undergo a successful collision.
  • ∴ higher ror at higher temp.
26
Q

What affect does a small increase in temp have on ror?

A
  • Large increase in ror as significant increase in no. molecules w enough energy to undergo successful collisions.
27
Q

Does increasing conc affect the shape of a M-B distribution?

A
  • Same basic shape.
  • Higher peak.
  • Emp (most probable energy) in same place.
28
Q

Using a M-B distribution how does increasing conc affect ror?

A
  • Higher conc, higher no. reactant molecules.
  • Overall area under increases.
  • ∴ more shaded area above Ea.
  • Increase in no. molecules which have energy to undergo successful collision increases.
  • ∴ higher ror.
29
Q

How is Ea affected by increasing conc?

A
  • Higher conc more area of reactant molecules that have Ea.
30
Q

Does incresing temp or conc have a more significant affect on ror?

A
  • Increasing temp.

Chemistry A-Level (5 decks)

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