Photochemical reaction Questions in English

(D) . The rate of this photochemical reaction is independent of the concentration of the reactants.
Therefore,it is a zero order reaction.

(C) The law of photochemical equivalence,also known as the $Stark-Einstein$ law,states that each molecule of a substance absorbs one quantum of radiation in a primary photochemical process. This law was proposed by $Johannes$ $Stark$ and $Albert$ $Einstein$ independently. Therefore,the correct option is $(C)$.

(B) In a photochemical reaction,the rate of formation of the excited species $AB^*$ is governed by the primary photochemical process.
According to the Stark-Einstein law of photochemical equivalence,the rate of a primary photochemical process is directly proportional to the intensity of the absorbed light $(I)$.

(B) In a photochemical reaction,the rate of the primary process is directly proportional to the intensity of the absorbed light $(I)$.
The reaction is $AB + h\nu \rightarrow AB^*$.
The rate of formation of the excited species $AB^*$ depends on the number of photons absorbed per unit time,which is represented by the intensity of light $I$.
Therefore,the rate of formation of $AB^*$ is proportional to $I$.

(B) The ratio of the number of molecules reacting or dissociating in a given time to the number of quanta of light absorbed in the same time is defined as the Quantum efficiency or Quantum yield.
It is denoted by the symbol $\phi$.
Therefore,the correct option is $(B)$.

(A) The energy of one mole of photons is given by the formula $E = \frac{h c N_A}{\lambda}$.
Substituting the given values:
$E = \frac{(6.62 \times 10^{-27} \ erg \ s) \times (3 \times 10^{10} \ cm \ s^{-1}) \times (6.02 \times 10^{23} \ mol^{-1})}{\lambda}$
$E = \frac{11.95572 \times 10^6}{\lambda} \ erg \ mol^{-1}$
$E = \frac{1.196 \times 10^8}{\lambda} \ erg \ mol^{-1}$.

(B) Silver nitrate $(AgNO_3)$ is a light-sensitive compound.
When exposed to light,it undergoes a photochemical decomposition reaction:
$2AgNO_3(aq) \xrightarrow{h\nu} 2Ag(s) + 2NO_2(g) + O_2(g)$.
Due to this decomposition,it is stored in dark-coloured bottles to prevent exposure to sunlight.

(C) Photochemical reactions are driven by the absorption of light energy (photons) rather than thermal energy.
Therefore,the rate of a photochemical reaction is generally independent of temperature,unlike thermal reactions where the rate increases significantly with an increase in temperature.