rate of a chemical reaction computed as the ratio of a measured change in amount or concentration of substance to the time interval over which the change occurred

instantaneous rate of a chemical reaction at t = 0 s (immediately after the reaction has begun)

rate of a chemical reaction at any instant in time, determined by the slope of the line tangential to a graph of concentration as a function of time

measure of the speed at which a chemical reaction takes place

mathematical representation defining reaction rate as change in amount, concentration, or pressure of reactant or product species per unit time

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Chemistry 2e · 12.1 Chemical Reaction Rates

Chemical Reaction Rates: practice problems

3 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.

Exercises 1
What is the difference between average rate, initial rate, and instantaneous rate?
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Exercises 3
In the nuclear industry, chlorine trifluoride is used to prepare uranium hexafluoride, a volatile compound of uranium used in the separation of uranium isotopes. Chlorine trifluoride is prepared by the reaction $Cl_{2} (g) + 3F_{2} (g) ⟶ 2ClF_{3} (g) .$ Write the equation that relates the rate expressions for this reaction in terms of the disappearance of Cl₂ and F₂ and the formation of ClF₃.
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Exercises 5
A study of the rate of the reaction represented as $2 A ⟶ B$ gave the following data:
Time (s) 0.0 5.0 10.0 15.0 20.0 25.0 35.0
[A] (M) 1.00 0.775 0.625 0.465 0.360 0.285 0.230
(a) Determine the average rate of disappearance of A between 0.0 s and 10.0 s, and between 10.0 s and 20.0 s.
(b) Estimate the instantaneous rate of disappearance of A at 15.0 s from a graph of time versus [A]. What are the units of this rate?
(c) Use the rates found in parts (a) and (b) to determine the average rate of formation of B between 0.00 s and 10.0 s, and the instantaneous rate of formation of at 15.0 s.
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Key terms · 5

average rate: rate of a chemical reaction computed as the ratio of a measured change in amount or concentration of substance to the time interval over which the change occurred
initial rate: instantaneous rate of a chemical reaction at t = 0 s (immediately after the reaction has begun)
instantaneous rate: rate of a chemical reaction at any instant in time, determined by the slope of the line tangential to a graph of concentration as a function of time
rate of reaction: measure of the speed at which a chemical reaction takes place
rate expression: mathematical representation defining reaction rate as change in amount, concentration, or pressure of reactant or product species per unit time

Learn 12.1 on the whiteboard

The tutor teaches the whole section, drawing it out step by step and answering your questions as you go.

Read 12.1 in the textbook · This section on openstax.org

Chemical Reaction Rates: practice problems

3 problems from the book, with its answers. Check your working, or have any of them explained to you on the whiteboard.

Exercises 1

What is the difference between average rate, initial rate, and instantaneous rate?

Exercises 3

In the nuclear industry, chlorine trifluoride is used to prepare uranium hexafluoride, a volatile compound of uranium used in the separation of uranium isotopes. Chlorine trifluoride is prepared by the reaction $Cl_{2} (g) + 3F_{2} (g) ⟶ 2ClF_{3} (g) .$ Write the equation that relates the rate expressions for this reaction in terms of the disappearance of Cl₂ and F₂ and the formation of ClF₃.

Exercises 5

A study of the rate of the reaction represented as $2 A ⟶ B$ gave the following data:

Time (s)	0.0	5.0	10.0	15.0	20.0	25.0	35.0
[A] (M)	1.00	0.775	0.625	0.465	0.360	0.285	0.230

(a) Determine the average rate of disappearance of A between 0.0 s and 10.0 s, and between 10.0 s and 20.0 s.

(b) Estimate the instantaneous rate of disappearance of A at 15.0 s from a graph of time versus [A]. What are the units of this rate?

(c) Use the rates found in parts (a) and (b) to determine the average rate of formation of B between 0.00 s and 10.0 s, and the instantaneous rate of formation of at 15.0 s.

Key terms · 5

average rate: rate of a chemical reaction computed as the ratio of a measured change in amount or concentration of substance to the time interval over which the change occurred
initial rate: instantaneous rate of a chemical reaction at t = 0 s (immediately after the reaction has begun)
instantaneous rate: rate of a chemical reaction at any instant in time, determined by the slope of the line tangential to a graph of concentration as a function of time
rate of reaction: measure of the speed at which a chemical reaction takes place
rate expression: mathematical representation defining reaction rate as change in amount, concentration, or pressure of reactant or product species per unit time

Learn 12.1 on the whiteboard

The tutor teaches the whole section, drawing it out step by step and answering your questions as you go.

Read 12.1 in the textbook · This section on openstax.org