Question

Identify the pair of gases which have same number of molecules at S.T.P?

• A. 11 g of $CO_{2}$ and 14 g of $N_{2}$
• B. 16 g of $O_{3}$ and 16 g of $CH_{4}$
• C. 5 g of $H_{2}$ and 40 g of $CH_{4}$
• D. 28 g of $N_{2}$ and 22 g of $CO_{2}$

Hint:

Same Moles = Same Molecules. Just divide the given mass by the molar mass!

Answer 1

The Correct Option is C

Step 1: Concept
According to Avogadro's Law, equal moles of any gas contain the same number of molecules at S.T.P.

Step 2: Meaning
Calculate moles (Mass Molecular Weight) for Option (C): Moles of $H_{2}$ = $5 / 2 = 2.5$ moles. Moles of $CH_{4}$ = $40 / 16 = 2.5$ moles.

Step 3: Analysis
Since both gases in Option (C) have exactly 2.5 moles, they contain an equal number of molecules.

Step 4: Conclusion
Option (C) is the correct pair.
Final Answer: (C)