Question 1

These questions concern the Maxwell-Boltzmann energy distribution shown below.

What is the best way to describe the activation energy, Ea, of a reaction?


  A  

the average energy of the particles that react

  B  

the minimum energy required for a reaction to occur

  C  

the energy difference between the reactants and products

  D  

the energy produced by the particles that react

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Question 2

How does the addition of a catalyst to a reaction affect the shape of the Maxwell-Boltzmann distribution curve?

  A  

there is no change

  B  

the peak moves to the left and is higher

  C  

the peak moves to the right and is lower

  D  

the total area under the curve increases

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Question 3

The reaction pathway diagram below illustrates the energies of the reactants, the products and the transition state of a reaction.

Which expression represents the activation energy of the forward reaction?

  A  

E1 - E2

  B  

E2 - E1

  C  

E2 - E3

  D  

E3 - E2

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Question 4

In the diagram, curve X was obtained by observing the decomposition of 100 cm3 of 1.0 mol dm-3 hydrogen peroxide, catalysed by manganese(IV) oxide.

Which alteration to the original experimental conditions would produce curve Y?

  A  

adding some 0.1 mol dm-3 hydrogen peroxide

  B  

adding water

  C  

lowering the temperature

  D  

using less manganese(IV) oxide

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Question 5

Two reactions are shown.

        Reaction 1:  N2(g) + 3H2(g) ⇌ 2NH3(g)

        Reaction 2:  2O3(g) ⇌ 3O2(g)

In reaction 1, a finely powdered iron catalyst is used.

In reaction 2, a vaporised tetrachloromethane catalyst in ultraviolet light is used.

Which statement about the catalysts used is correct?

  A  

both reaction 1 and reaction 2 use a heterogeneous catalyst

  B  

both reaction 1 and reaction 2 use a homogeneous catalyst

  C  

reaction 1 uses a heterogeneous catalyst and reaction 2 uses a homogeneous catalyst

  D  

reaction 1 uses a homogeneous catalyst and reaction 2 uses a heterogeneous catalyst

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Question 6

Hydrogen ions catalyse the hydrolysis of esters.

Which statement is correct?

  A  

the hydrogen ions act as a heterogeneous catalyst

  B  

the hydrogen ions are in the same phase as the reactants

  C  

the hydrogen ions are used up in the reaction

  D  

the hydrogen ions have no effect on the activation energy of the reaction

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Question 7

The diagram shows the Boltzmann distribution of energies in a gas. The gas can take part in a reaction with an activation energy, Ea. The gas is maintained at a constant temperature.

Which statement is correct?

  A  

if a catalyst is added, peak P will be lower and Ea will move to the left

  B  

if a catalyst is added, peak P will be lower and Ea will move to the right

  C  

if a catalyst is added, peak P will be the same and Ea will move to the left

  D  

if a catalyst is added, peak P will be the same and Ea will move to the right

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Question 8

Iodine and propanone react according to the following equation.

I2(aq) + CH3COCH3(aq) ➔ CH3COCH2I(aq) + HI(aq)

If the concentration of propanone is increased, keeping the total reaction volume constant, the rate of the reaction also increases.

What could be the reason for this?

  A  

a greater proportion of collisions is successful at the higher concentration

  B  

the particles are further apart at the higher concentration

  C  

the particles have more energy at the higher concentration

  D  

there are more collisions between reactant particles per second at the higher concentration

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Question 9

A Maxwell-Boltzmann curve shows the distribution of molecular energies in a reaction system.

When the temperature in this system is increased, the peak is

  A  

higher and further to the right

  B  

higher and further to the left

  C  

lower and further to the right

  D  

lower and further to the left

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Question 10

What is the main reason for the increase in reaction rate with increasing temperature?

  A  

the activation energy decreases

  B  

the activation energy increases

  C  

more molecules have an energy greater than the activation energy

  D  

the molecules collide more frequently

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Question 11

The figure shows a typical energy distribution for particles of an ideal gas in a sealed container at a fixed temperature.

Which of the following statements is true?

  A  

position A represents the mean energy of a molecule in the container

  B  

addition of a catalyst moves the position of Ea to the right

  C  

the area under the curve to the right of Ea represents the number of molecules with enough energy to react

  D  

the position of the peak of the curve at a higher temperature is further away from both axes

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Question 12

The Maxwell-Boltzmann distribution of molecular energies in a sample of gas at a fixed temperature is shown.

Which letter represents the mean energy of the molecules?

  A  
  B  
  C  
  D  

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