Kinetics Flashcards

1
Q

How can we calculate the rate of reactions from experiments?

A

Measure the concentration of reactants or products (titration)

Measure the volume of gas produced as a product (using a gas syringe)

Measure the change in masses of substances formed (using a balance to weigh the reactants and products)

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2
Q

How do you calculate the rate of reaction from a graph?

A

Gradient = change in y / change in x = the rate of reaction

Initial rate when t=0

Draw a tangent——> calculate gradient = rate of reaction

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3
Q

What is the rate of reaction?

A

The change in the concentration of a reactant or product over time.

Rate = change in concentration / time

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4
Q

What factors affect rate of reactions?

A
Temperature 
Pressure
Concentration
Surface area
Presence of a catalyst
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5
Q

How does temperature effect rate of reaction?

A

Increasing the temperature increases the kinetic energy of the molecules and therefore the number of successful collisions increase

Hence the rate of reaction increases

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6
Q

How does pressure effect the rate of reaction?

A

Increasing the pressure increases the rate of reaction of gases

Therefore the molecules are closer together and more likely to collide and have a successful collisions with energy in excess of the activation energy.
Therefore collisions are more frequent and the rate of reaction increases

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7
Q

How does concentration effect the rate of reaction?

A

Increasing the concentration increase the number of molecules of a reactant.
Therefore there are more molecules closer together and can collide with and increased number of collisions so the rate of reaction increases

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8
Q

How does surface area effect the rate of reaction?

A

Increasing the surface are increases the area where a reaction can occur so the rate of reaction increases

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9
Q

How does he presence of s catalyst effect the rate of reaction?

A

Catalysts provide an alternative pathway for a reaction to take place. The pathway has a lower activation energy and therefore the reaction happens faster.

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10
Q

What does the maxwell boltzman curve show?

A

The distribution of molecular energies in a gas at a constant temperature.

The majority of molecules have an average energy.

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11
Q

On a Maxwell Boltzmann curve what does the area under the graph represent and the Ea line?

A

Area under the graph: the total number of molecules in the sample

Ea: activation energy therefore only molecules greater than the activation energy can react

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12
Q

What happens to the Maxwell Boltzmann curve when temperature is increased?

A

At higher temperature the kinetic energy of molecules increases

The peak moves to the right and is lower

  1. Molecules move faster as they have more kinetic energy
  2. Therefore a higher proportion of molecules have an energy above the activation energy.
  3. There are more successful collisions
  4. The rate of reaction increases
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13
Q

What happens to the Maxwell Boltzmann curve when a catalyst is present?

A

Catalysts lower the activation energy of a reaction

Ea moves to the left

  1. More molecules have an energy in excess of the new lower activation energy
  2. More successful collisions in a given time
  3. Rate of reaction increases
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14
Q

What are the roles of catalysts?

A

Increase the rate of reaction without being used up in the reactions

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15
Q

How does a catalyst work

A

By providing an alternative pathway for a reaction to take place with a lower activation energy

They react forming an intermediate but are then regenerated later in the reaction

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16
Q

What is a homogenous catalyst?

A

A catalyst which is in the same state as the reactants

17
Q

What is a heterogenous catalyst?

A

A catalyst in a different state to the reactants