Question

Which of the following organohalogens contains the largest number of molecules?

• A. 1g of $CH_3Br$
• B. 1g of $CH_2Br_2$
• C. 1g of $CHBr_3$
• D. 1g of $CBr_4$

Hint:

For a fixed mass, the lightest molecule always wins the "most molecules" race.

Answer 1

The Correct Option is A

Step 1: Concept
The number of molecules is proportional to the number of moles ($n$), where $n = \text{mass} / \text{molar mass}$.

Step 2: Analysis
Since the mass is fixed at 1g for all options, the substance with the smallest molar mass will have the highest number of moles and thus the largest number of molecules.

Step 3: Calculation of Molar Masses
$CH_3Br$ has only 1 Bromine atom, while others have 2, 3, or 4. Bromine is very heavy ($\approx 80$ u), so $CH_3Br$ has the lowest molar mass.

Step 4: Conclusion
1g of $CH_3Br$ contains the most molecules. Final Answer: (A)