Final answer:
The reaction CCL₄ → CH₄ and 2H₂ + O₂ → 2H₂O + Au are not possible according to Dalton's atomic theory, as they violate the law of conservation of mass.
Step-by-step explanation:
The reaction CCL₄ → CH₄ is not possible according to Dalton's atomic theory as it violates the law of conservation of mass. Dalton's theory states that atoms cannot be created or destroyed in a chemical reaction. Here, chlorine atoms are disappearing and hydrogen atoms are appearing without adherence to this principle. Reaction N₂ + 3H₂ → 2NH₃ is possible because it follows the atom conservation rule where nitrogen and hydrogen atoms are rearranged into ammonia without any loss or gain of atoms. The reaction 2H₂ + O₂ → 2H₂O + Au is not possible as it suggests gold (Au) is formed from a reaction involving only hydrogen and oxygen, again violating the conservation of atoms.