Question

Which gives a maximum yield of \[{C_2}{H_5}Cl\,\]?
A. \[{C_2}{H_6} + C{l_2}(excess)\xrightarrow{{h\nu .light}}{C_2}{H_5}Cl + HCl\]
B. \[{C_2}{H_6}(excess) + C{l_2}\xrightarrow{{h\nu .light}}{C_2}{H_5}Cl + HCl\]
C. \[{C_2}{H_6} + C{l_2}\xrightarrow{{h\nu .light}}{C_2}{H_5}Cl\]
D. \[{C_2}{H_6} + C{l_2}\xrightarrow{{dark}}{C_2}{H_5}Cl + HCl\]

Answer 1

Hint: In this question, we first determine the type of changes that take place because of this reaction. These changes may be both physical and chemical in nature. Then the conditions that promote these changes must be incorporated to get the maximum yield in any given reaction.

Complete step by step answer:
In these given reactions, chlorine reacts with ethane in different conditions, and ethyl chloride is formed as a product. In these reactions as external force sunlight is used. from sunlight, the photon particles will be absorbed to carry out this reaction. Now in presence of sunlight the substitution of hydrogen by chlorine takes place. But in this reaction, only mono choro products (ethyl chloride) will not be formed and some amount of dichloro and trichloro products will also be formed.
So, to increase the amount of ethyl chloride, an excess amount of ethane should be used, therefore the reaction should be as follows,
 \[{C_2}{H_6}(excess) + C{l_2}\xrightarrow{{h\nu .light}}{C_2}{H_5}Cl + HCl\]

So, the correct option is, B.

Additional information:
The quantum yield \[\left( \Phi \right)\] of a radiation-induced process is the number of times a specific event occurs per photon absorbed by the system. It can be described as a ratio of the number of photons emitted to the number of photons that are absorbed. Quantum yield \[\left( \Phi \right)\] can also be described as a measure of the efficiency of photon emission as defined by the ratio of the number of photons emitted to the number of photons absorbed.
The mathematical formula is Quantum Yield
\[ = \dfrac{{No.\,of\,molecules\,decomposed}}{{no.\,of\,photons\,absorbed}}\]

Note: Another way to get the maximum yield is the introduction of a catalyst. It helps to achieve an acceptable yield in an acceptable time. The catalyst lowers the activation energy of the reactions and makes the rate of the reaction faster also increases the yield of the product.