CHEMISTRY

JAMB 2010 - Question 45

Chemistry 2010 JAMB Past Questions - Question 45: The final products of the reaction between methane and chlorine in the presence of ultraviolet light are hydrogen chloride and

Choose the correct answers from the options given.
The final products of the reaction between methane and chlorine in the presence of ultraviolet light are hydrogen chloride and
A:
B:
C:
D:
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Correct Answer

C

Explanation

When methane (CH?) reacts with chlorine (Cl?) in the presence of ultraviolet light, a series of **substitution reactions** can occur, replacing hydrogen atoms in the methane molecule with chlorine atoms. The final products can vary depending on the conditions and the extent of the reaction.

However, considering the options you provided:

* **Trichloromethane (CHCl?):** This compound, also known as chloroform, is not the **final** product. It can indeed be formed as an intermediate product, but depending on the reaction conditions and duration, the substitution can continue, leading to further chlorination.
* **Dichloromethane (CH?Cl?):** Similar to trichloromethane, this compound (dichloromethane) can be an intermediate product but not necessarily the final outcome.
* **Tetrachloromethane (CCl?):** This molecule, also known as carbon tetrachloride, is the **most likely final product** under conditions where complete chlorination occurs. All hydrogen atoms in the methane molecule are replaced by chlorine atoms.
* **Chloromethane (CH?Cl):** This compound (chloromethane) is the **initial product** formed during the first substitution reaction. However, the reaction doesn't stop there, and further chlorine atoms can replace the remaining hydrogen atoms.

Therefore, while all the options can appear at different stages of the reaction, the **most likely final product** under complete chlorination conditions is **tetrachloromethane (CCl?)**.

Here's a summary of the reaction sequence:

CH? + Cl? (hv) → CH?Cl + HCl (initial product)

CH?Cl + Cl? (hv) → CH?Cl? + HCl

CH?Cl? + Cl? (hv) → CHCl? + HCl

CHCl? + Cl? (hv) → CCl? + HCl (final product)

The extent of chlorination (up to which intermediate product it stops) depends on factors like the ratio of methane to chlorine, the intensity of the ultraviolet light, and the reaction time.