Question

Which of the following contains the largest number of oxygen atoms?
 $1g$ of $O$ atoms, $1g$ of $O_2,$ $1g$ of ozone $O_3.$
(A) $1g$ of $O.$
(B) $1g$ of $O_2.$
(C) $1g$ of $O_3.$
(D) All have the same number of atoms.

Answer 1

Hint: We know that the ozone is made up of ordinary oxygen. The only difference is that ozone is made up of three oxygen atoms, while the stuff we breathe is made up of only two oxygen atoms. Solar rays high in the atmosphere convert oxygen into ozone.

Complete answer:
The total number of atoms in any element is defined in terms of Avogadro’s number. You might be thinking what Avogadro number is, so let’s check it out first. Avogadro’s number is defined as the number of units in one mole of any substance (defined as its molecular weight in grams)is equal. The units may be electrons, atoms, ions, or molecules, depending on the nature of the substance. The value of the Avogadro constant was chosen so that the mass of one mole of a chemical compound (in grams) is numerically equal to the average mass of one molecule of the compound, in Daltons.
Atomic mass of $O$ atom $=16g$ and Number of atoms in $10g$ of $O$ atoms $=6.023\times {10}^{23}$
So, Number of atoms in $1g$ of $O$ atom $={\displaystyle \frac{6.023\times {10}^{23}}{16}}=0.376\times {10}^{23}$ atoms.
Molecular mass of $O_2=32g$ and Number of atoms in $32g$ of $O_2$ atoms $=2\times 6.023\times {10}^{23}$
So, Number of atoms in $1g$ of $O2={\displaystyle \frac{2\times 6.023\times {10}^{23}}{32}}=0.376\times {10}^{23}$ atoms.
Molecular mass of $O_3=32g$ and Number of atoms in $48g$ of $O_3$ atoms $=3\times 6.023\times {10}^{23}$
So, Number of atoms in $1g$ of $O_3={\displaystyle \frac{3\times 6.023\times {10}^{23}}{48}}=0.376\times {10}^{23}$ atoms.
Therefore, the correct answer is option D, i.e. all have the same number of atoms.

Note:
Remember that if two different compounds have the same Avogadro’s number, it only means that only their number of molecules are the same nothing else and it will contain the same number of atoms from which that compound is made of in the same molecular ratio.