3.2.2 Reaction Rates Flashcards

1
Q

Effect of concentration on the rate of reaction

A
  • as conc increases there are more particles per unit volume
  • more collisions per second resulting in more reactions per second
  • increase in the rate of reaction
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2
Q

Effect of gas pressure on rate of reaction

A
  • as pressure increases there are more particles per unit volume
  • more collisions per second resulting in more reactions per second
    -increase in rate of reaction
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3
Q

Effect of particle size on rate of reaction

A
  • small particles have a larger surface area
  • more collisions per second
  • more collisions resulting a reaction
  • rate of reaction increases
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4
Q

Effect of temperature on rate of reaction

A
  • particles have greater kinetic energy
  • more collisions per second
  • more collisions result in reactions
  • more particles will have more energy than the activation energy
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5
Q

What is the definition of rate of reaction?

A

Rate = change in concentration / time
moldm-3s-1

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6
Q

What conditions must be satisfied for a chemical reaction to occur by collisions?

A
  • must collide
  • with sufficient kinetic energy
  • in the correct orientation
  • must have equal to or over the activation energy
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7
Q

What is the activation energy?

A

The minimum amount of energy required for a chemical reaction to occur

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8
Q

What is the role of a catalyst?

A
  • increases reaction rate without being used up in the overall reaction
  • allows a reaction to proceed on an alternative pathway with lower activation energy
  • (therefore more particles have greater than the activation energy)
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9
Q

What are heterogeneous catalysts?

A
  • catalysts that are in a different phase as the reactants
  • e.g. solid catalyst in liquid reaction
  • e.g. solid iron in the Haber process to make gaseous ammonia
  • nitrogen + hydrogen -> ammonia
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10
Q

Why are catalysts important?

A
  • great economic importance and benefits for increased sustainability
  • by lowering temperatures and reducing energy demand from combustion of fossil fuels with resulting decrease in CO2 emissions
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11
Q

What is a homogeneous catalyst?

A
  • catalysts that are in the same phase as the reactants
  • e.g liquid catalyst in a liquid reaction
  • e.g. concentrated sulphuric acid added to an esterification reaction
  • e.g. enzymes in body
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12
Q

What is the Boltzmann distribution curve?

A
  • shows how the energies of the particles are distributed in the sample or substance being used
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13
Q

What are the rules of the Boltzmann distribution curve?

A
  • no particles have no energy and no particles have the maximum amount of energy
  • the curve never touches the axis (within 1/2 square of axis)a
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14
Q

What is does the area under the Boltzmann distribution curve show?

A
  • total area under the curve = total number of particles in sample
  • area under graph greater than Ea = number of particles that can react - successful collisions per second
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15
Q

Draw the Boltzmann distribution curve

A

See notes

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16
Q

Draw the Boltzmann distribution curve with a catalyst (lower Ea)

A

See notes
More particles with energy greater than or equal to Ea, so more successful collisions per second

17
Q

Draw the Boltzmann distribution curve for lower, medium and higher temperature

A

See notes