Question

Number of atoms in 12 g is equal to :

• A. oxygen atoms in 11 g $C{O}_2$
• B. hydrogen atoms in 4 g $C{H}_4$
• C. nitrogen atom in 46 g $N_2{O}_4$
• D. sulphur atom in 79 g $N{a}_2{S}_2{O}_3$

Answer 1

Answer: (A)

$12g$ of ${}_{12}^{24}Mg(0.5mol)$ contains atoms
$=3.01\times 10^{23}$
(A) $11g$ of $C{O}_2(0.25mol)$ contains oxygen atom
$=0.50mol$
$=3.01\times 10^{23}$ atoms
(B) $4g$ of $C{H}_4(0.25mol)$ contain hydrogen atoms
$=1mol=6.02\times 10^{23}$ atoms
(C) $46g$ of $N_2{O}_4(0.5mol)$ contains nitrogen atom
$=2mol=2\times 6.02\times 10^{23}$ atoms
(D) $79g$ of $N{a}_2{S}_2{O}_3$ $(0.5mol)$ contains sulphur atoms $=1mol=6.02\times 10^{23}$ atom
(Molar mass of $C{O}_2,C{H}_4,N_2{O}_4$ and $N{a}_2{S}_2{O}_3$ are $44,16,92$ and $158gmo{l}^{-1})$