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Q.
Number of atoms in 12 g is equal to :
Some Basic Concepts of Chemistry
Solution:
$12\,g$ of $^{24}_{12}Mg (0.5\,mol)$ contains atoms
$=3.01 \times 10^{23}$
(A) $11\,g$ of $CO_{2}(0.25\,mol)$ contains oxygen atom
$=0.50\,mol$
$=3.01\times 10^{23}$ atoms
(B) $4\,g$ of $CH_{4}(0.25\,mol)$ contain hydrogen atoms
$=1\,mol=6.02\times10^{23}$ atoms
(C) $46\,g$ of $N_{2}O_{4}(0.5\,mol)$ contains nitrogen atom
$=2\,mol=2\times6.02\times10^{23}$ atoms
(D) $79\,g$ of $Na_{2}S_{2}O_{3}$ $(0.5\,mol)$ contains sulphur atoms $=1\,mol=6.02\times10^{23}$ atom
(Molar mass of $CO_{2}, CH_{4}, N_{2}O_{4}$ and $Na_{2}S_{2}O_{3}$ are $44, 16,92$ and $158\,g\,mol^{-1})$