14.3.2 The Arrhenius Equation

Question 1

The Arrhenius Equation

Answer 1

• The reaction rate increases as temperature increases.

* The relationship between the reaction rate and temperature is expressed by the Arrhenius equation.

Question 2

note

Answer 2

• The reaction rate increases as temperature increases.
• For example, light sticks react more slowly in ice water than at room temperature, and react even faster when placed in hot water.
• Food is refrigerated to slow down decomposition reactions.
• The relationship between the reaction rate and temperature is expressed by the Arrhenius equation.
• The Arrhenius equation relates the rate constant (k) to the frequency factor (A) and the fraction of collisions with
  enough energy to react (f). The frequency factor has a slight temperature dependence, but the fraction of collisions with enough energy to react has a strong temperature dependence.
• Taking the natural log of both sides of the Arrhenius equation yields the equation ln k = ln A – E a /RT. This equation is in the form of a line. Plotting ln k versus 1/T yields a line with slope = –E a /R. This equation can be used to find the activation energy (E a ) from a set of experimental data.

Question 3

What is 25°C in Kelvin?

Answer 3

298 K

Question 4

Which household appliance best illustrates applications of the work on kinetics performed by Arrhenius?

Answer 4

The refrigerator.

Question 5

Why do endothermic reactions proceed faster at high temperatures?

Answer 5

More kinetic energy is available for the reactants.

Question 6

How does an increase in temperature affect a chemical reaction?

Answer 6

The reaction speeds up.

Question 7

Which of the following graphs shows the log of rate vs. temperature?

Answer 7

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Question 8

What is the purpose of the Arrhenius equation?

Answer 8

The Arrhenius equation expresses the relationship between the reaction rate and temperature.

Question 9

Which of the following is the Arrhenius equation for reaction rate?

Answer 9

k = Ae ^−Ea/RT

Question 10

In the formula for the rate of a chemical reaction, which expression changes with temperature?

rate = k[A]^m[B]^n

Answer 10

k

Question 11

Light sticks activated at high temperature produce a brighter light than light sticks at room temperature or at low temperature. Yet, when a glowing light stick is placed into a freezer, the reaction stops. Why is this?

Answer 11

The reaction is temperature dependent. Lowering the temperature kills this reaction but raising the temperature will restore the reaction.

Question 12

The Arhenius Equation can be rearranged into the form of an equation of a straight line. What parameters are plotted in order to determine the Ea of a reaction by graphical method?

Answer 12

Plot ln of k versus the 1/T