10-minute Quiz : Chapter 52 Activation energy

Consider the reaction between sodium and cold water:

2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)

A student drew an energy profile for this reaction, as shown in the diagram. What is/are the mistakes in that student’s energy profile?

(1) The energy level of the reactants should be lower than that of the products.

(2) The state symbols of the chemical species involved in the reaction are missing.

(3) The label for the x-axis should be ‘Reaction coordinate’.

• A. (1) only
• B. (2) only
• C. (1) and (3) only
• D. (2) and (3) only

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NGSS.HS-PS1-4

The rate constants of a reaction at 500°C and 750°C are 0.113 s⁻¹ and 0.150 s⁻¹ respectively. What is the activation energy for the reaction? (Given: R = 8.31 J K⁻¹ mol⁻¹)

• A. 3.53 kJ mol⁻¹
• B. 7.44 kJ mol⁻¹
• C. 23.6 kJ mol⁻¹
• D. 49.8 kJ mol⁻¹

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NGSS.HS-PS1-5

In an experiment, the rate constants of a reaction at different temperatures are determined, and the data were used to plot the graph.

• A
• B
• C
• D

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NGSS.HS-PS1-5

If the activation energy for the forward reaction of a single-step reaction is 52 kJ mol⁻¹ and that for the backward reaction is 74 kJ mol⁻¹, what is the enthalpy change of the single-step reaction?

• A. 22 kJ mol⁻¹
• B. −22 kJ mol⁻¹
• C. 52 kJ mol⁻¹
• D. −52 kJ mol⁻¹

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NGSS.HS-PS1-4

What is the activation energy of a reaction whose rate constant increases by a factor of 100 upon increasing the temperature from 300 K to 360 K? (Given: R = 8.31 J K⁻¹ mol⁻¹)

• A. 35.5 kJ mol⁻¹
• B. 42.2 kJ mol⁻¹
• C. 53.3 kJ mol⁻¹
• D. 68.8 kJ mol⁻¹

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NGSS.HS-PS1-5

Suppose the activation energy of a reaction is 250 kJ mol⁻¹. If the rate constant at 300 K is k₁, and that at 320 K is k₂, how many times faster is the reaction at 320 K compared to that at 300 K? (Given: R = 8.31 J K⁻¹ mol⁻¹)

• A. 0.067
• B. 15.0
• C. 531
• D. 3 × 10²⁸

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NGSS.HS-PS1-5

Shown in the diagram are the Maxwell-Boltzmann distribution curves for a gaseous reaction system at three different temperatures. Which temperature, T₁, T₂ or T₃, is the lowest?

• A. T₁

• B. T₂

• C. T₃

• D. It cannot be determined.

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NGSS.HS-PS1-5

Which of the following statements explains why the rate of reaction increases as the temperature is increased?

• A. The rate constant of a reaction increases with temperature.
• B. The activation energy of a reaction increases with temperature.
• C. The concentration of reactants increases with temperature.
• D. The number of effective collisions between reactant particles per unit time increases with temperature.

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NGSS.HS-PS1-5

Consider the energy profile for a reversible reaction as shown in the diagram. What is the activation energy for the backward reaction of the reversible reaction?

• A. x

• B. y

• C. x + y

• D. x − y

Tags

NGSS.HS-PS1-4

Which of the graphs correctly shows the relationship between rate constant, k, of a reaction and temperature, T?

• A
• B
• C
• D

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NGSS.HS-PS1-5