Correct Answer – A
12 g of `._(12)^(24)Mg`(0.5 mol) contains atoms
`= 3.01xx10^(23)`
(A) 11 g of `CO_(2)`(0.25 mol) contains oxygen atom
`= 0.50 mol`
`=3.01xx10^(23)` atoms
(B) 4 g of `CH_(4)`(0.25 mol) contain hydrogen atoms
`= 1 mol = 6.02xx10^(23)`atoms
(C) 46 g of `N_(2)O_(4)`(0.5 mol) contains sulphur atoms
`=2 mol = 2xx6.02xx10^(23)` atoms
(D) 79 g of `Na_(2)S_(2)O_(3)` (0.5 mol) contains sulphur atoms = 1 mol = `6.02xx10^(23)` atom
(Molar mass of `CO_(2), CH_(4), N_(2)O_(4)` and `N_(2)S_(2)O_(3)` are 44, 16, 92 and `158 g mol^(-1)`

Correct Answer – A
Number of atoms = number of molecues `xx` specific
atoms in molecules
In` {:(24),(12):}` Mg number of atom `= =12/24 xx 6.022 xx 10^(23)xx1`
`=3.011xx 10^(23)` atoms
Number of `O_(2)` atoms in 11 `CO_(2)`
`= 11/44 xx 6.022 xx 10^(23)xx2`
`=3.011 xx 10^(23)` atoms