Question

The number of oxygen atoms in 4.4g of $C{O_2}$ is approximately:
A.$1.2 \times {10^{23}}$
B.$6 \times {10^{22}}$
C.$6 \times {10^{23}}$
D.$0.12 \times {10^{23}}$

Answer 1

1 mole of carbon dioxide contains $6.022 \times {10^{23}}$atoms and two oxygen atoms per $C{O_2}$ molecule. At a given mass, the number of moles can be calculated and using unitary method, the number of oxygen atoms in a specific amount of $C{O_2}$ can be determined.
Formula used: $moles = \dfrac{{given\,mass}}{{molar\,mass}}$

Complete step by step answer:
Moles is the unit of measurement of the amount of a substance as per International System of Units. It is defined as exactly Avogadro’s number i.e. $6.022 \times {10^{23}}$particles, particles can either be atoms or molecules. It can be calculated by the ratio of given mass to molar mass for any molecule or compound.
We know that the molar mass of $C{O_2}$ is 44gms.
We are provided the given mass as 4.4gms.
From these two values, we can determine number of moles by the following formula
$moles = \dfrac{{given\,mass}}{{molar\,mass}}$
Putting the values in it, we get=
$moles = \dfrac{{4.4}}{{44}} = 0.1mol$
We know, 1mole of $C{O_2}$has $6.022 \times {10^{23}}$atoms (Avogadro’s number)
Therefore, 0.1mol of $C{O_2}$has 2 oxygen atoms in it, so it will contain
$\dfrac{{6.022 \times {{10}^{23}} \times 2 \times 0.1}}{1} = 1.2 \times {10^{23}}$
So, the number of oxygen atoms in 4.4g of $C{O_2}$ is approximately $1.2 \times {10^{23}}$.

Hence, the correct option is (A).

Note:
We saw that two atoms of oxygen are present in one molecule of carbon dioxide, it is known as atomicity. It is the number of atoms that constitute a molecule. It can be determined by the ratio of molecular mass to atomic mass.