Chapter 14, Problem 1DE

(a)

Interpretation Introduction

To determine: The experiment to determine the rate law and rate constant of the given reaction.

Answer to Problem 1DE

Solution: The rate law of the reaction is determined by measuring the extent of light absorbed by the solution by using spectrophotometer.

Explanation of Solution

Given

The chemical equation for the given hypothetical reaction is,

$a\text{A}+b\text{B}\to c\text{C}+d\text{D}$

The reactants present in the reaction are water soluble.

The reactants B and D are colorless.

The reactant A has absorption maxima at $510\text{nm}$ .

The reactant C has absorption maxima at $640\text{nm}$ .

The rate law of the given reaction is determined by measuring the concentration of reactants at regular intervals of time in the given reaction. The concentration of the reactants in the given reaction is measured by measuring the extent of light absorbed by the sample at regular intervals of time by spectrophotometer. This provides the dependence of rate of the given reaction on the concentration of the reactant which gives the value of rate constant.

Conclusion

The rate law of the reaction is determined by measuring the extent of light absorbed by the solution by using spectrophotometer.

(b)

Interpretation Introduction

To determine: The experiment to determine the activation energy of the given reaction; also the challenges in carrying out this experiment.

Answer to Problem 1DE

Solution: The activation energy is calculated by plotting the graph of $\ln k$ versus $\frac{1}{T}$ for the given reaction. The challenge is to measure concentrations of reactant at different temperatures.

Explanation of Solution

The activation energy of the given reaction is determined by using the formula,

$\ln k=-\frac{E_{\text{a}}}{RT}+\ln A$

Where,

• $k$ is the rate constant of the reaction.
• $E_{\text{a}}$ is the activation energy of the reaction.
• $R$ is the gas constant.
• $T$ is the temperature of the reaction.
• $A$ is the pre exponential factor.

The activation energy of the reaction is calculated by determining rate constant of the given reaction at different values of temperature experimentally. The slope of the graph drawn between the $\ln k$ versus $\frac{1}{T}$ gives the value of activation energy.

The challenge faced in experimental determination of activation energy is to measure the rate constant of the reaction at different temperatures.

Conclusion

The activation energy is calculated by plotting the graph of $\ln k$ versus $\frac{1}{T}$ for the given reaction. The challenge is to measure concentrations of reactant at different temperatures.

(c)

Interpretation Introduction

To determine: If the given water soluble catalyst Q is the homogeneous catalyst for the given reaction or not.

Answer to Problem 1DE

Solution: The regeneration of catalyst at the end of the reaction and the increase in the rate of reaction confirms the homogeneous catalysis.

Explanation of Solution

Given

The reactants present in the reaction medium are water soluble.

The homogeneous catalyst is the catalyst which is present in the reaction medium in the same phase as the reactants are present.

Since, the given catalyst is water soluble. Therefore, it is in the same phase as the reactants in the reaction medium.

The given catalyst is the homogeneous catalyst for the given reaction or not is tested by determining the nature of catalyst experimentally. The rate of the reaction before addition of catalyst and after addition of catalyst is compared which gives the confirmation of activity of the catalyst. The regeneration of catalyst in the same phase as it was added is the proof of homogeneous catalysis.

Conclusion

The regeneration of catalyst at the end of the reaction and the increase in the rate of reaction confirms the homogeneous catalysis.

(d)

Interpretation Introduction

To determine: The experiment required to know about the reaction profile of the reaction catalysis by catalyst Q.

Answer to Problem 1DE

Solution: The energy profile diagram is drawn for the reaction in presence of catalyst and in absence of catalyst.

Explanation of Solution

The reaction change in the reaction profile of the given reaction is studied by plotting the graph of energy versus the reaction progress in presence of catalyst and in the absence of catalyst.

The activation energy is the minimum energy required to start the reaction. The addition of catalyst increases the rate of reaction by lowering the activation energy of the reaction. The difference in the activation energy of catalyzed and uncatalyzed reaction gives the exact activity of the catalyst.

Conclusion

The energy profile diagram is drawn for the reaction in presence of catalyst and in absence of catalyst.