Chemical Kinetics

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What is the condition for considering an intermediate compound as a stationary state?

When k1 >> k2

When k2 = 0

When k2 >> k1 (correct)

When k1 = k2

Which type of reaction involves the absorption of light energy to initiate the reaction?

Photophysical process

Parallel reaction

Photochemical reaction (correct)

Thermodynamically favored reaction

What is the characteristic of a parallel reaction?

Multiple reactions occur simultaneously (correct)

The reaction is thermodynamically favored

The reaction occurs in the dark

Only one reactant is involved

What is the energy associated with each photon in a photochemical reaction?

hv Signup and view all the answers

What is the term for the process in which a molecule absorbs light energy and transitions to a higher energy level?

Photophysical process Signup and view all the answers

What is the primary reason for the dependence of photochemical reaction rates on the intensity of radiation?

The rate of absorption of photons Signup and view all the answers

In the photochemical combination of H and Cl, what is the role of the excited chlorine molecule (Cl2*)?

It decomposes to form chlorine free radicals (Cl) Signup and view all the answers

Why do different photochemical reactions have different rates?

Because they have different activation energies Signup and view all the answers

What is the effect of temperature on the rate of light-initiated reactions?

It has no effect on the rate Signup and view all the answers

What is the role of hv in the photochemical combination of H and Cl?

It is the light absorption step that forms the excited chlorine molecule (Cl2*) Signup and view all the answers

What is the significance of the negative free energy change in a thermochemical reaction?

It implies that the reaction is spontaneous and can occur without any external energy input. Signup and view all the answers

Which step is highly endothermic and limits the feasibility of the subsequent step in the reaction mechanism?

Step (III) in the reaction mechanism Signup and view all the answers

What is the reason for the lower values of HBr formation per photon of light absorbed in the given reaction mechanism?

The high recombination rate of bromine free radicals Signup and view all the answers

What is the significance of the quantum yield in a photochemical reaction?

It measures the efficiency of the reaction Signup and view all the answers

Which of the following applications is not a direct result of photochemical reactions?

Electroplating in industries Signup and view all the answers

What is the condition for equation (3) to be valid?

k1 << k2 Signup and view all the answers

In parallel reactions, what is the characteristic of the reactants?

They have different orders of reaction Signup and view all the answers

What is the energy required for a reactant molecule to cross the energy barrier in a photochemical reaction?

Activation energy Signup and view all the answers

What is the term for the process in which a molecule absorbs light energy and transitions to a higher energy level, and then loses its energy through a chemical reaction?

Photophysical process Signup and view all the answers

What is the characteristic of photochemical reactions that distinguishes them from thermal reactions?

They do not occur in dark Signup and view all the answers

What is the primary reason for the decrease in HBr formation per photon of light absorbed in the given reaction mechanism?

Most of the bromine free radicals recombine to give Br2 molecule Signup and view all the answers

Which step is responsible for the regeneration of free radicals in the given reaction mechanism?

Chain termination step Signup and view all the answers

What is the significance of the delta G value in photochemical reactions?

It may be positive or negative Signup and view all the answers

What is the role of light energy in photochemical reactions?

It is converted into free energy of the products Signup and view all the answers

What is the application of photochemistry in the electronic industry?

Photoetching Signup and view all the answers

What is the reason for the dependence of photochemical reaction rates on the intensity of radiation?

The amount of energy absorbed by the reactant molecules Signup and view all the answers

What is the characteristic of the excited molecule (Cl2*) in the photochemical combination of H and Cl?

It is a highly reactive species Signup and view all the answers

Why do some photochemical reactions have a higher yield of products than others?

Because of the chain reaction mechanism Signup and view all the answers

What is the significance of the wavelength of photon in a photochemical reaction?

It determines the amount of energy absorbed Signup and view all the answers

What is the role of light in a photochemical reaction?

To initiate the reaction Signup and view all the answers