You visited us 3 times! Enjoying our articles? Unlock Full Access!

Byju's Answer

Standard IX

Chemistry

Photochemical Reaction

Photochemical...

Question

Photochemical reactions have the following characteristics:

These requires photons to interact with chemical species

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

Each molecule absorbs only one photon to get itself excited

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

It is not necessary for an excited molecule to show always chemical change

No worries! We‘ve got your back. Try BYJU‘S free classes today!

Light is essential for photochemical reaction

Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses

Open in App

Solution

The correct options are
A These requires photons to interact with chemical species
B Light is essential for photochemical reaction
C Each molecule absorbs only one photon to get itself excited
Photochemical reaction, a chemical reaction initiated by the absorption of energy in the form of light. The consequence of molecules' absorbing light is the creation of transient excited states whose chemical and physical properties differ greatly from the original molecules.

Option A is correct. Chemical species absorb photons and create new compounds as in the photosynthesis in plants in which sunlight energy is stored in the form of chemical energy by forming carbohydrates from atmospheric carbon dioxide and water and releasing molecular oxygen as a byproduct.
Option B is correct. Each molecule take only one photons.
Option C is wrong. As per definition, the chemical and physical properties of the excited molecule is different from original molecules.
Option D is correct. Light energy (consisting of photons) is necessary for the reaction.

Hence, A, B and D is correct.

Suggest Corrections

Similar questions

Q. Many chemical reactions can be brought about by the absorption of light of suitable wavelength. Such reactions are known as photochemical reactions. In a photochemical reaction, only the first step is photochemical and the rest are thermal. The energy of the absorbed photon is used for the chemical conversions. For the photochemical combination of hydrogen and chlorine to form hydrogen chloride, the following mechanism was suggested.

C l_{2} (h v) - - \to 2 C l^{∙}

. . . . . . (i)

C l^{∙} + H_{2} k_{1} \to H C l + H^{∙}

. . . . . . (ii)

H^{∙} + C l_{2} k_{2} \to H C l + C l^{∙}

. . . . . . (iii)

2 C l^{∙} k_{3} \to C l_{2}

. . . . . . (iv)
In the photochemical reaction of

H_{2}

and

C l_{2}, C l_{2}

absorbs at wavelength of 488 nm.When the

C l_{2}

gas is irradiated with a 60 watt lamp that emits radiation with 80% efficiency, 4.1 mmol of

H C l

were formed in 10 sec. Calculate the quantum yield for the reaction. (write the value to the nearest integer)

Q. In the photochemical decomposition of acetaldehyde, one photon of absorbed light decomposes one molecule of

C H_{3} C H O

into

∙ C H_{3} a n d ∙ C H O

. If

^{'} I_{a b s}^{'}

is the intensity of light absorbed in the reaction. Write the rate equation for this photochemical decomposition. (Note: the first step in the photochemical reaction is temperature independent)
Calculate

[∙ C H_{3}] a n d \frac{d [C O]}{d t}

assuming steps (ii) to (iv) given are same and

[∙ C H_{3}], [∙ C H_{3} C O]

are under steady state.

Q. When light is absorbed a photochemical change may take place. When molecules are excited by a striking quantum (unit) of light :

Q. The chemical reactions which are initiated by are called photochemical reactions.

$O_{2}$ undergoes photochemical dissociation into one normal and one excited atoms. The excited atom has 1.967 eV more energy than normal. The dissociation of $O_{2}$ into two normal atoms requires 498 KJ mole-1. Then the maximum wavelength required for photochemical dissociation of $O_{2}$ is

Join BYJU'S Learning Program