Question

Which of the following contains maximum number of molecules?

• A. \(0.4\) g \(\text{H}_2\) gas
• B. \(3.2\) g of \(\text{O}_2\) gas
• C. \(16.8\text{ dm}^3\) of \(\text{H}_2\) gas at STP
• D. \(11.2\text{ dm}^3\) of \(\text{O}_2\) gas at STP

Hint:

Convert each sample to moles; the largest number of moles has the most molecules.

Answer 1

The Correct Option is C

Step 1: Plan:
Count molecules in units of $N_A$.

Step 2: Steps:
Sample A has $0.2N_A$ molecules and B has $0.1N_A$. At STP, one mole occupies $22.4$ dm$^3$, so C has $\frac{16.8}{22.4}N_A = 0.75N_A$ and D has $0.5N_A$. The largest is C.

Final Answer:
Sample C has the most molecules, option (C). \[ \boxed{16.8\ \text{dm}^3\ \text{of H}_2\ \text{at STP}} \]