Kinetics of Homogeneous Processes. Individual assignments

6.The quantum yield of the photolysis of gaseous HI to H2 and I2 by light with a wavelength of 253.7 nm equals 2. Calculate the number of moles of HI decayed upon absorbing 300 J of light with this wavelength.

Assignment 11

1.What are the signs, by which the complex reactions can be distinguished from the simple ones?

2.What are the reasons for chain termination in the reactions proceeding by a chain mechanism?

3.What is the basis for the statement that the reaction, H2 + Br2 2HBr,

is not bimolecular as it was considered for a long time?

4.Write down the differential equation for the rate of changing the concentration of the starting compound, A, and the rate of accumulation of the products, B and C, in the reaction,

5. The rate of a chemical reaction is expressed by the following equation:

To which type of reactions does this reaction belong? Give its schematic representation.

6. For the reaction,

,

the sum of the rate constants equals 0.01 min–1. Determine the concentration of A under the stipulation that its concentration became 0.1 mol/L in 230 min after the reaction start.

Assignment 12

1.What reactions are considered as parallel?

2.Formulate the Einsteinʹs principle of photochemical equivalence.

3.Show graphically the change in the concentrations of reagents along with the lapse of time in the reaction,

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4.What equation describes the rate of the reversible reaction,

5.The reaction,

NO2Cl = NO2 +1/2Cl2, proceeds through the following mechanism:

Assuming that the concentration of chlorine is stationary, show that the empirical kinetic constant under the stipulation of a first-order reaction equals 2k1.

6.The reaction,

is 20% complete in 500 s. In what time it will be 60% complete?

Assignment 13

1.What is the general expression of the rate of reversible reactions written in general form?

2.What postulates are used upon deducing the kinetic equations for reversible and parallel reactions?

3.Show graphically the changes in the concentrations of reagents along with the lapse of time in the following consecutive reaction:

4.What is the conceptual basis of the method of stationary concentrations? Explain using an example.

5.Can the quantum yield of a photochemical reaction exceed one? If the answer is positive, then in what cases it can?

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6.The concentrations of the starting compound in different time moments for the reaction of isomerization of -oxycrotonic ester into acetoacetic ester are given below in the table.

Find the rate constants for the direct and reverse reactions.

Assignment 14

1.What are differences in the kinetics of simple and complex reactions?

2.What equations are used for calculation of the rate constants of reversible reactions of the first order?

3.Represent schematically the kinetic curves for parallel reaction of the first order in the case when k1 = k2.

4.The rate of a particular reaction is described by the equation,

To which type of complex reactions does it belong? Give its schematic representation.

5. Prove that the equality,

d A d C , d d

is applicable under the stationary conditions to the reaction,

6. For the reaction,

the following data are obtained:

The initial concentration of A is а = 0.1823 mol/L. Determine the rate constants for the direct and reverse reactions.

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Assignment 15

1.What is called "the mechanism of a chemical reaction"?

2.What are the main points of the method of stationary concentrations.

3.What are the reasons for chain termination in the reactions, which proceeds by a chain mechanism?

4.Write down the differential equation describing the rate of the reaction,

5.For the reaction,

write down the relationships between the rates and the rate constants, k1 + k2, under the condition of inequality of the initial concentrations of reactants.

6.What will be the concentration of А in 4.3 min after the start in the reaction,

,

considering that its initial concentration was 44.7 mol/L, and the sum, k1 + k2 + k3, equals 0.115 min–1.

Assignment 16

1.Name differences in the kinetics of simple and complex reactions.

2.What signs indicate that the reaction goes by a chain mechanism?

3.What equation is used for calculation of the rate constants of first-order parallel reactions?

4.Show graphically the change in the concentration of reagents over time in the consequtive reaction,

5.The rate of some chemical reaction is described by the following equation:

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To which type of reactions does this reaction belong? Give its schematic representation.

6.The conversion of NH4CNS to (NH2)2CS is a reversible monomolecular reaction. Calculate the rate constants of the direct and reverse reactions at 450°C, using the following experimental data:

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REFERENCES

1.A.G. Stromberg and D.P. Semchenko, Fizicheskaya khimiya (Physical Chemistry), М.: Vysshaya shkola, 2003, 527 p.

2.Kratkii kurs fizicheskoi khimii (Brief Course of Physical Chemistry), Textbook for institutions of higher education (Ed.: S.N. Kondratiev), М.: Vysshaya shkola, 1978, 312 p.

3.A.G. Golikov, Rukovodstvo po fizicheskoi khimii (Instruction Manual on Physical Chemistry), М.: Vysshaya shkola, 1988, 383 p.

4.N.M. Emmanuel and D.G. Knorre, Kurs khimicheskoi kinetiki (Course of Chemical Kinetics), Textbook for institutions of higher education, М.: Vysshaya shkola, 1984, 463 p.

5.G.M. Pagenkov and V.P. Lebedev, Khimicheskaya kinetika i kataliz (Chemical Kinetics and Catalysis), Textbook for institutions of higher education, М.: Khimiya, 1985, 590 p.

6.I.V. Kudryashov and G.S. Karetnikov, Sbornik primerov i zadach po fizicheskoi khimii (Workbook of Exercises and Problems on Physical Chemistry), М.: Vysshaya shkola, 1991, 527 p.

7.Kratkii spravochnik fiziko-khimicheskikh velichin (Short Handbook of Physicochemical Values (Eds.: A.A. Ravdel and A.M. ponomareva), Leningrad: Khimiya, 1983, 232 p.

8.Fizicheskaya khimiya v voprosakh i otvetakh (Physical Chemistry in Questions and Answers) (Eds.: K.V. Topchieva and N.V. Fedorovich), M.: Moscow State University, 1981, 24 p.

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KINETICS OF HOMOGENEOUS

PROCESSES

Contributors:

Oleg N. Kadkin, Associate Professor

Yuriy G. Galyametdinov, Full Professor

Galina V. Bulidorova, Associate Professor

Ksenia A. Romanova, Assistant Professor

Responsible for publishing A. A. Konopleva

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