Question
Among the following, choose the ones with equal number of atoms.
A. 212 g of ${Na}_{2}{CO}_{3}(\text{ }s)$ [molar mass $= 106\text{ }g$ ]
B. 248 g of ${Na}_{2}O(s)$ [molar mass $= 62\text{ }g$ ]
C. 240 g of $NaOH(s)$ [molar mass $= 40\text{ }g$ ]
D. 12 g of $H_{2}(\text{ }g)$ [molar mass $= 2\text{ }g$ ]
E. 220 g of ${CO}_{2}(\text{ }g)$ [molar mass $= 44\text{ }g$ ]
Choose the correct answer from the options given below :
Options
Solution
Sol. [Key Concept: Equal number of atoms — mole concept calculation]
Number of atoms $= \frac{\text{~}\text{given mass}\text{~}}{\text{~}\text{molar mass}\text{~}} \times$ atomicity $\times N_{A}$
A. $\frac{212}{106} \times 6 \times N_{A} = 12{\text{ }N}_{A}$
B. $\frac{248}{62} \times 3 \times N_{A} = 12{\text{ }N}_{A}$
C. $\frac{240}{40} \times 3 \times N_{A} = 18\text{ }N\text{ }A$
D. $\ \frac{12}{2} \times N_{A} \times 2 = 12{\text{ }N}_{A}$
E. $\frac{220}{44} \times N_{A} \times 3 = 15\text{ }N\text{ }A$
$A,B$ and $D$ have same number of atoms
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