Complete Chlorination of Methane Produces Four HCl Molecules

Steps:

• Methane (CH4) undergoes free radical substitution with Cl2 in sunlight.
• Each hydrogen atom is sequentially replaced by chlorine.
• With large excess Cl2, substitution continues until all four hydrogens are replaced.
• Balanced equation: CH4 + 4Cl2 → CCl4 + 4HCl.

Why D is correct:

• The stoichiometry of the complete substitution reaction yields 4 moles of HCl per mole of CH4.

Why the others are wrong:

• A: Corresponds to monochlorination (CH3Cl + HCl), incomplete with excess Cl2.
• B: Corresponds to dichlorination (CH2Cl2 + 2HCl), not full substitution.
• C: Corresponds to trichlorination (CHCl3 + 3HCl), stops short of complete reaction.

Final answer: D