15. Chemical Kinetics

Average Rate of Reaction

Introduction to reaction rates | Kinetics | AP Chemistry | Khan Academy

Use the following equation and graph to answer questions 1 and 2.
Hydrogen iodide decomposes at 410 °C, according the reaction:
2 HI1g2¡H21g2 + I21g2
The graph shows how the concentration of HI changes over time.

What is the average rate of loss of HI over the time period
0–40 s (LO 14.1)
(a) 7.5 * 10-3 M>s (b) 4.8 * 10-3 M>s
(c) 3.0 * 10-2 M>s (d) 3.5 * 10-3 M>s

Consider the following hypothetical aqueous reaction:
A1aq2S B1aq2. A flask is charged with 0.065 mol of A
in a total volume of 100.0 mL. The following data are
collected:
Time (min) 0 10 20 30 40
Moles of A 0.065 0.051 0.042 0.036 0.031
(b) Calculate the average rate of disappearance
of A for each 10-min interval in units of M>s.

Consider the reaction:
2 N2O( g) ¡ 2 N2( g) + O2( g)
a. Express the rate of the reaction in terms of the change in
concentration of each of the reactants and products.

Consider the reaction:
NO2( g) ¡ NO( g) + 1 2 O2( g)
The tabulated data were collected for the concentration of NO2
as a function of time:

a. What is the average rate of the reaction between 10 and 20 s?
Between 50 and 60 s?

Consider the reaction:
2 HBr( g) ¡ H2( g) + Br2( g) 
a. Express the rate of the reaction in terms of the change in
concentration of each of the reactants and products.

The rate of disappearance of HCl was measured for the
following reaction:
CH3OH1aq2 + HCl1aq2¡CH3Cl1aq2 + H2O1l2
The following data were collected:
Time (min) 3HCl 4 1M2
0.0 1.85
54.0 1.58
107.0 1.36
215.0 1.02
430.0 0.580
(b) Calculate
the average rate of reaction for the entire time for the data
from t = 0.0 min to t = 430.0 min.

Consider the reaction:
2 HBr( g) ¡ H2( g) + Br2( g) 
c. If the volume of the reaction vessel in part b was 1.50 L, what
amount of Br2 (in moles) was formed during the first 15.0 s of
the reaction?

Consider the reaction:
C4H8( g) ¡ 2 C2H4( g)
The tabulated data were collected for the concentration of C4H8
as a function of time:

a. What is the average rate of the reaction between 0 and 10 s?
Between 40 and 50 s?

Consider the following hypothetical aqueous reaction:
A1aq2S B1aq2. A flask is charged with 0.065 mol of A
in a total volume of 100.0 mL. The following data are
collected:
Time (min) 0 10 20 30 40
Moles of A 0.065 0.051 0.042 0.036 0.031
(a) Calculate the number of moles of B at each time in
the table, assuming that there are no molecules of B at
time zero and that A cleanly converts to B with no intermediates.<img src="https://lightcat-files.s3.amazonaws.com/problem_images/06b291dee25eefd8-1666264397964.jpg" alt="" />

Average Rate of Reaction Concept 1

The stoichiometry is 2 C3H6 to 6 H2O. Therefore the rate of production of water will be 6/2 that of C3H6.

Correct, use of the stoichiometry of the reaction to relate rates.

 The definition of the rate with respect to each reactant and product must reflect the stoichiometry of the reaction. 

The rate of consumption of C3H6 in the following reaction is 0.45 M/s. Calculate the rate of production of H2O. 2 C3H6 + 2 NH3 + 3 O2 &#8594; 2 CH2CHCN + 6 H2O

You study the rate of a reaction, measuring both the concentration
of the reactant and the concentration of the
product as a function of time, and obtain the following
results:
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/66b0d9a9ffad3cdf-1666264973446.jpg" alt="" />
Which chemical equation is consistent with these
data:
(i) A → B, (ii) B → A, (iii) A → 2 B,
(iv) B → 2 A?

Consider the reaction:
NO2( g) ¡ NO( g) + 1 2 O2( g)
The tabulated data were collected for the concentration of NO2
as a function of time:

b. What is the rate of formation of O2 between 50 and 60 s?

(b) The reaction
2 NO1g2 + Cl21g2¡2 NOCl1g2 is carried out in
a closed vessel. If the partial pressure of NO is decreasing
at the rate of 56 torr/min, what is the rate of change of the
total pressure of the vessel?

For the reaction 2 A( g) + B( g) ¡ 3 C( g),
b. when A is decreasing at a rate of 0.100 M>s, how fast is
B decreasing? How fast is C increasing?

The rate of disappearance of HCl was measured for the
following reaction:
CH3OH1aq2 + HCl1aq2¡CH3Cl1aq2 + H2O1l2
The following data were collected:
Time (min) 3HCl 4 1M2
0.0 1.85
54.0 1.58
107.0 1.36
215.0 1.02
430.0 0.580
(a) Calculate the average rate of reaction, in M>s, for the
time interval between each measurement.

The rate of disappearance of HCl was measured for the
following reaction:
CH3OH1aq2 + HCl1aq2¡CH3Cl1aq2 + H2O1l2
The following data were collected:
Time (min) 3HCl 4 1M2
0.0 1.85
54.0 1.58
107.0 1.36
215.0 1.02
430.0 0.580
(c) Which is greater,
the average rate between t = 54.0 and t = 215.0 min, or
between t = 107.0 and t = 430.0 min?

Consider the reaction:
8 H2S( g) + 4 O2( g) ¡ 8 H2O( g) + S8( g)
Complete the table.

Average Rate of Reaction Example 2

(a) What are the units usually used to express the rates of
reactions occurring in solution?

Kinetics: Initial Rates and Integrated Rate Laws

Chemical Kinetics:  Calculating Average Rates and Instantaneous Rates

Average versus Instantaneous Reaction Rates

Consider the reaction:
H2( g) + Br2( g) ¡ 2 HBr( g)
The graph shows the concentration of Br2 as a function of time.
<img src="https://lightcat-files.s3.amazonaws.com/problem_images/d6ba0d5ff5f539eb-1674523502761.jpg" alt="" />
a. Use the graph to calculate each quantity:
(i) the average rate of the reaction between 0 and 25 s

Consider the reaction:
2 H2O2(aq) ¡ 2 H2O(l ) + O2( g)
The graph shows the concentration of H2O2 as a function of
time.

Use the graph to calculate each quantity:
d. If the initial volume of the H2O2 is 1.5 L, what total amount
of O2 (in moles) is formed in the first 50 s of reaction?

Consider the following reaction:2 H2O2 (aq) → 2 H2O (l) + O2 (g)Calculate the rate of the reaction between 25 sec and 65 sec.<img src="https://static.studychannel.pearsonprd.tech/courses/general-chemistry/thumbnails/images/a3b82eca"class="fr-fic fr-dii">

A 1.50 L sample of gaseous HI having a density of 
0.0101 g>cm3 is heated at 410 °C. As time passes, the 
HI decomposes to gaseous H2 and I2. The rate law is 
-Δ3HI4>Δt = k3HI42, where k = 0.031>1M ~ min2 at 
410 °C. 
(b) What is the partial pressure of H2 after a reaction time 
of 8.00 h?

The isomerization of methyl isonitrile 1CH3NC2 to acetonitrile
1CH3CN2 was studied in the gas phase at 215 C,
and the following data were obtained:
Time (s) 3CH3nC4 1M2
0 0.0165
2000 0.0110
5000 0.00591
8000 0.00314
12,000 0.00137
15,000 0.00074
(b) Calculate
the average rate of reaction over the entire time of the
data from t = 0 to t = 15,000 s.<img src="https://lightcat-files.s3.amazonaws.com/problem_images/13580ab1dbbc05ee-1666025942319.jpg" alt="" />

Average Rate of Reaction Example 1

A flask is charged with 0.100 mol of A and allowed to react
to form B according to the hypothetical gas-phase reaction
A1g2¡B1g2. The following data are collected:
Time (s) 0 40 80 120 160
Moles of A 0.100 0.067 0.045 0.030 0.020
(c)
Which of the following would be needed to calculate the
rate in units of concentration per time: (i) the pressure of
the gas at each time, (ii) the volume of the reaction flask,
(iii) the temperature, or (iv) the molecular weight of A?<img src="https://lightcat-files.s3.amazonaws.com/problem_images/b9f50909ea02b273-1666270739535.jpg" alt="" />

For each of the following gas-phase reactions, indicate
how the rate of disappearance of each reactant is related
to the rate of appearance of each product:
(c) N21g2 + 3 H21g2¡2 NH31g2

Average Reaction Rate and Unique Average Reaction Rate

For the reaction 2 A( g) + B( g) ¡ 3 C( g),
a. determine the expression for the rate of the reaction in terms
of the change in concentration of each of the reactants and
products.

Consider the reaction:
2 HBr( g) ¡ H2( g) + Br2( g) 
b. In the first 25.0 s of this reaction, the concentration of HBr
dropped from 0.600 M to 0.512 M. Calculate the average rate
of the reaction during this time interval.

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1. Intro to General Chemistry

2. Atoms & Elements

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4. BONUS: Lab Techniques and Procedures

5. BONUS: Mathematical Operations and Functions

6. Chemical Quantities & Aqueous Reactions

7. Gases

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[BOOK CHEM] Clutch Version

Intro to Chemical Kinetics

Chemical Kinetics is the study of factors affecting reaction rates, which examines the speed by which reactants are consumed to make products.

Average (General) Rate is the change in the concentration of a compound over a period of time.

Arrhenius Equation

The Arrhenius Equation&nbsp;illustrates the temperature dependence of the rate constant k.&nbsp;

Rate Law

Rate Law represents an equation for a chemical reaction that connects the reaction rate with the concentrations or pressures of the reactants and the rate constant.&nbsp;

Factors Influencing Rates

There are 4 major factors that directly influence how fast or slow a reaction proceeds.

Stoichiometric Rate Calculations

When the rate of one compound is know, the rate of another compound is calculated through rate-to-rate comparison.

Collision Theory

According to Collision Theory:chemical reaction is successful when 2 energetic reactants successfully collide.

Integrated Rate Law

When we include the variable of time to our Rate Law then we obtain the Integrated Rate Laws.&nbsp;

Catalyst

Catalyst is a substance that increases the rate of reaction by lowering the Activation Energy (Ea) of a reaction.

Instantaneous Rate

<div title="Page 1">&nbsp;Instantaneous Rate is the rate a reaction at any particular point in time.</div>

Reaction Mechanism

<div title="Page 1">A Reaction Mechanism is a step-by-step sequence of elementary steps by which an overall chemical change occurs.</div>

Half-Life

Half-Life is the time it takes for half&nbsp;of a reactant to decay in a certain time period.

Energy Diagrams

Energy Diagram represents a curved plot illustrating the energies of reactants, products and transition states of a reaction.