cyclohexenylallylmalononitrile at 135°C in different periods of time have been changed as follows:

Determine the reaction rate constant using the graphical method.

Task 6

1.Explain the term "molecularity of a chemical reaction". Can the molecularity be greater or smaller than the reaction order?

2.Specify the unit for the rate constant of a second-order reaction.

3.What is the relationship between the half-life of a reaction and the initial concentration of a starting reagent in the case of 2-nd and 3-rd order reactions?

4.Upon studying the kinetics of a chemical reaction, the kinetic curves with different concentrations of reagents have been obtained. Which of the methods of determination of the reaction order is most effective in this case?

5.The reaction, 2HCrO4–+3HSO3– + 5H+ → 2Cr3+ + 3SO42– +5H2O, is described by the following kinetic equation:

w = k[HCrO4–][3HSO3–]2[H+].

Why is the rate of this reaction not proportional to the number of ions of each sort in accordance with the stoichiometric coefficients in the chemical equation?

6.The conversion of benzoyl peroxide into diethyl ether (1st order reaction) at 60°С proceeds by 75.2% in 10 minutes. Calculate the reaction rate constant.

Task 7

1.What are called the reaction order with respect to one of the individual reactants and the overall kinetic order of a reaction?

2.Can the numerical values of rate constants be compared with each other for reactions of different orders?

3.What experimental data are necessary for determining the reaction order?

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4.Show graphically the general character of the time dependence of the concentration of a final product for a zero-order reaction.

5.Write down and integrate the kinetic equation of the reaction, the order of which equals 1/2. Deduce the expression for the half-life of this reaction.

6.The concentration of NH3 upon its decomposition in different periods of time have been changed as follows:

Determine the reaction order and the reaction rate constant.

Task 8

1.Give the expression for the rate of the irreversible reaction, the mechanism of which is described by the chemical equation,

2А + В → С.

2.Specify the unit for the rate constant of a third-order reaction.

3.Can one determine the order of a chemical reaction, knowing stoichiometric coefficients in the chemical equation of this reaction?

4.What experimental data do reveal the influence of intermediate compounds and final products on the reaction rate?

5.Find the expression for the half-life, τ1/2, of a third-order reaction for the case when the initial concentrations of starting reagents are equal.

6.The concentrations of HCN and С3H7СНО in the reaction between propionic aldehyde and hydrocyanic acid (aqueous solution at 25о) in different periods of time terms have been changed as follows:

The initial concentrations of НСN and С3H7СНО were 0.1 and 0.06 mol/L, respectively. Determine the reaction order and calculate the reaction rate constant.

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Task 9

1.In which cases is the reaction rate defined as the change in the concentration of reactants per unit time?

2.Can the molecularity and reaction order be fractional values?

3.How to demonstrate that a particular reaction is of the first order?

4.What information about a chemical reaction can you get from the time dependence of the concentration of a reactant?

5.The experimentally established kinetic equation for the reaction

2NO + O2 → 2NO2 can be expressed as follows:

d[NO2 ] = k[NO]2[O2 ]. dτ

Can one make the following conclusions: а) The reaction is trimolecular.

b)The reaction proceeds in one stage.

c)The overall reaction order is 3.

d)The reaction is of the first order with respect to NO and O2.

7.The concentration of BrO– in the reaction ClO– + Br– → BrO– + Cl– has been changed in different periods of time as follows:

The concentrations of NaClO and KBr in the reaction mixture at τ = 0 equaled 0.00323 and 0.002508 mol/L, respectively. Determine the reaction order and calculate the rate constant?

Task 10

1.What does the expression, w = − ddCτA , means for the reaction, A→ B? Can the reaction rate be negative?

2.How does the half-life of a first-order reaction depend on the concentration of reactants?

3.Which methods of determination of the reaction order are related to the group of differential methods?

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4.If the order of the reaction, А + В → С, is determined under the

condition, СА = СВ, then which of the order values, the order with respect to an individual reactant or the overall reaction order, is obtained using such an approach?

5.Get the expression for the rate constant of a gas-phase reaction of the

general type, А → В + С + D, using the values of the initial (p0) and current (p) pressure of gases in the system.

6.The rate constant of the second-order reaction,

СН3СООС2Н5 + NaOH → CH3COONa + C2H5OH,

is 5.4 L/(mol × min). The initial concentrations of ester and alkali were 0.04 and 0.02 mol/L, respectively. Find the amount of ester consumed within 10 min after the reaction start.

Task 11

1.Write down the expression for the rate constant of a second-order reaction at unequal concentration of starting reagents.

2.How can the rate of a chemical reaction be determined experimentally?

3.If the method of flooding (Oswaldʹs isolation method) is used for determination of the reaction order, then which type of the reaction orders, the overall order or the order with respect to one of the reactants, is determined with applying such an approach?

4.In which coordinates should the kinetic diagram be drawn in order to get a linear dependence of the function of concentration on time for a first-order reaction?

5.For the reaction, I– + OСl– → Cl– + OI–, the following kinetic equation is derived experimentally: w = k [I–] [OСl–]. What is the total reaction order? Give explanation of your answer. Suggest a mechanism for this reaction.

6.In the reaction of isomerization of ethylene dichloride

the concentration of trans-isomer in different periods of time varied as follows:

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What is the order of the reaction? What amount of time does the isomerization of the half-quantity of trans-isomer require?

Task 12

1.What is understood under the term "molecularity of a chemical reaction"? To what kind of reactions is this concept applicable?

2.If k = 0.3 L/(mol min), then what is the reaction order? Express k in cm3/(mol s).

3.In what kind of reactions the concentration of a reactant linearly decreases with time?

4.Illustrate schematically the kinetic curve for the change of the concentration of the substance, B, in the following irreversible chemical reaction: A → B.

5.For the reaction Br– + OСl– → Cl– + OBr–, the following kinetic equation is derived experimentally: w = k [Br–] [OСl–]. What is the total reaction order? Give explanation of your answer. Suggest a mechanism for this reaction.

6.In the reaction 2Сe4+ + As3+ → 2Ce3+ + As4+, the concentration of Ce4+ in different periods of time varied as follows:

Determine the order of the reaction and its kinetic constant.

Task 13

1.How is the basic postulate of chemical kinetics formulated?

2.Can numerical values of the rate constants for reactions of different orders be compared with each other?

3.What experimental data point to the influence of intermediate substances and final products on the reaction rate?

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4.The order of the reaction, А + В + С → D, was determined under the

condition, СА0 ≠ СА0 ≠ СА0. Which kind of the reaction order, the order with respect to a particular reactant or the total reaction order, is determined in this case?

5.Show graphically the dependence of the concentration of a reaction product on time for the case of a second-order reaction.

6.For the reaction, 2Ce4+ + As3+ → 2Ce3+ + As4+, determine the order of

the reaction and its kinetic constant using the following experimental data on the equal concentrations of Ce4+ and As3+.

Task 14

1.In which cases the reaction rate is defined as the change in concentration of reactants per unit time?

2.How does the concentration of a reaction product change over the course of a first-order reaction?

3.How does the half-life of a first-order reaction depend on the initial concentration of a reactant?

4.Upon studying the kinetics of a reaction, a series of values of the changes in the concentration of a reactant in time is obtained. What method of determination of the reaction order is most efficient in this case?

5.Compare the rate constants of two first-order reactions for the case when the half-time of the first reaction exceeds by two times the half-life of the second reaction.

6.For the reaction

С6Н5-С≡С-СООNa + I2 → С6Н5-IC=СI-COОNa the following experimental kinetic data were obtained:

Determine the order of the reaction and calculate its kinetic constant.

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Task 15

1.Write down the mathematical expression for the actual rate of a chemical reaction.

2.What methods for determination of the reaction order are related to the group of differential methods?

3.Show schematically the kinetic curves for reactants and reaction products in a zero-order reaction.

4.The rate of the homogeneous reaction, 2 NO (g.) + О2 (g.) → 2NO2 (g.) is described by the equation, w = k pNO pO2. What is the order of this reaction.

5.Using the values of the initial (pо) and total (p) pressure of gases in the system, find the expression for the kinetic constant, k, for the gas-phase

reaction, A → B + C.

6.For the reaction, С2Н4Сl2 (g.) → С2Н3Сl (g.) + НСl (g.), it is determined that k = 3.1 × 10 s–l at 450°C. Calculate the time required for one half of the initial quantity of ethylene dichloride to react. What is the amount of time required for the completion of 90% of the reaction?

Task 16

1.Which of the most common technological problems can be solved using the kinetic methods?

2.What experimental data are necessary for determination of the reaction order?

3.What is the order of a reaction with a kinetic constant of k = 0.1 L/(mol min)?

4.Show graphically the dependence of the concentration of reaction products on time for a first-order reaction.

5.Get the expression for the half-life of a third-order reaction under the condition that the concentrations of reactants are equal.

6.The rate constant of the reaction,

СН3СООС2Н5 + NaOH → СН3СООNa + С2Н5OH,

is 5.4 L/(mol s). What amount of ester is consumed in 10 min after the reaction start under the condition that a = b = 0.02 mol/L?

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