NEET 2025 · ChemistryPrevious Year Question
Among the following, choose the ones with an equal number of atoms. A. 212 g of \ce{Na2CO3}(s) [molar mass = 106 g] B. 248 g of \ce{Na2O}(s) [molar mass = 62 g] C. 240 g of \ce{NaOH}(s) [molar mass = 40 g] D. 12 g of \ce{H2}(g) [molar mass = 2 g] E. 220 g of \ce{CO2}(g) [molar mass = 44 g] Choose the correct answer from the options given below:
- A.B, C and D only
- B.B, D and E only
- C.A, B and C only
- D.A, B and D only✓
Correct Answer
(D) A, B and D only
Solution & Explanation
\textbf{Answer:} (D) A, B and D only \textbf{Solution:} Total atoms $= (\text{moles})\times(\text{atoms per formula unit})$, in units of $N_A$: A. $\dfrac{212}{106}=2$ mol \ce{Na2CO3} $\times 6 = 12$ B. $\dfrac{248}{62}=4$ mol \ce{Na2O} $\times 3 = 12$ C. $\dfrac{240}{40}=6$ mol \ce{NaOH} $\times 3 = 18$ D. $\dfrac{12}{2}=6$ mol \ce{H2} $\times 2 = 12$ E. $\dfrac{220}{44}=5$ mol \ce{CO2} $\times 3 = 15$ A, B and D each give $12\,N_A$ atoms.
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