Question

Which from following quantity of different gases contains maximum number of molecules?

• A. \(7\text{ }\mathrm{g}\text{ }\mathrm{N}_{2}\)
• B. \(2\text{ }\mathrm{gH}_{2}\)
• C. \(8\text{ }\mathrm{gO}_{2}\)
• D. \(20\text{ }\mathrm{gNO}_{2}\)

Hint:

The number of molecules is proportional to the number of moles, so compare mass divided by molar mass for each gas.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
Number of molecules \(= n\times N_A\), so the sample with the largest number of moles has the most molecules.
Moles \(n = \dfrac{\text{mass}}{\text{molar mass}}\).

Step 2: Calculation
\(\text{N}_2\): \(7/28 = 0.25\) mol
\(\text{H}_2\): \(2/2 = 1\) mol
\(\text{O}_2\): \(8/32 = 0.25\) mol
\(\text{NO}_2\): \(20/46 \approx 0.43\) mol

Step 3: Compare the options
The largest number of moles is 1 mol of \(\text{H}_2\), so 2 g of \(\text{H}_2\) has the maximum number of molecules.

Final Answer:
2 g of hydrogen contains the maximum number of molecules. \[ \boxed{\text{(B) }\text{2 g H}_2} \]