Question

Mass of one atom of oxygen is:
A. $\dfrac{{16}}{{6.023 \times {{10}^{23}}}}{\rm{ g}}$
B. $\dfrac{{32}}{{6.023 \times {{10}^{23}}}}{\rm{ g}}$
C. $\dfrac{3}{{6.023 \times {{10}^{23}}}}{\rm{ g}}$
D. 8 u

Answer 1

The mass of 1 mole of a compound is known as molar mass. The mole concept gives an estimate about the number of atoms present in 1 molar mass of a compound. Using the mole concept formula, we can then find the number of atoms in the molar mass of the compound. From there, we can calculate the weight of 1 atom of the substance given.
Formula used: ${\rm{Moles = }}\dfrac{{{\rm{weight}}}}{{{\rm{molar mass}}}}$ where molar mass is the mass of 1 mole of a compound.

Complete step by step answer:
The mole concept states that 1 mole of an atom or molecule consists of the same amount of particles in it. The number of particles in 1 mole is known as Avogadro’s number. It is equal to $6.023 \times {10^{23}}$ atoms or molecules. The mass of 1 mole is different for every compound. In case of oxygen, we know that the molar mass of an oxygen atom is ${\rm{16 g mo}}{{\rm{l}}^{ - 1}}$.
According to the mole concept formula,
${\rm{1 mole oxygen = }}6.023 \times {10^{23}}{\rm{ atoms}}$
The weight of 1 mole of oxygen is 16g. So,
$\Rightarrow 16{\rm{g oxygen = }}6.023 \times {10^{23}}{\rm{ atoms}}$
$\Rightarrow {\rm{6}}{\rm{.023 \times 1}}{{\rm{0}}^{{\rm{23}}}}{\rm{ atoms = 16g oxygen}}$
From here, we can calculate the weight of 1 atom of oxygen as:
$\Rightarrow {\rm{1 atom oxygen = }}\dfrac{{16}}{{6.023 \times {{10}^{23}}}}{\rm{g}}$

$\therefore$ The correct option is option A, i.e. $\dfrac{{16}}{{6.023 \times {{10}^{23}}}}{\rm{g}}$.

Note:
The molar mass of a molecule will be different from the molar mass of an atom of the same element. For example, oxygen as an atom has molar mass of ${\rm{16 g mo}}{{\rm{l}}^{ - 1}}$ while oxygen molecule has a molar mass of ${\rm{32 g mo}}{{\rm{l}}^{ - 1}}$. This is because oxygen molecules are present as ${{\rm{O}}_{\rm{2}}}$. So, the mass is double the mass of an atom of oxygen. While solving the question, we should be aware if the question contains an atom of the element or a molecule. The weight of 1 atom can also be written with the unit u, where $1{\rm{u = }}\dfrac{1}{{6.023 \times {{10}^{23}}}}{\rm{g}}$ . So, the weight of 1 atom of oxygen will be 16 u.