Question

The number of atoms in \[{\text{60g}}\] of neon \[{\text{[Ne]}}\] are:
(A) \[6 \times 6.023 \times {10^{23}}\] atoms
(B) \[2 \times {\text{6}}{\text{.023}} \times {\text{1}}{{\text{0}}^{23}}\] atoms
(C) \[5 \times {\text{6}}{\text{.023}} \times {\text{1}}{{\text{0}}^{23}}\] atoms
(D) \[3 \times {\text{6}}{\text{.023}} \times {\text{1}}{{\text{0}}^{23}}\] atoms

Answer 1

Hint: Avogadro’s Number represents the total number of atoms or molecules present in one mole of any substance. It is a constant value and is used in calculating the number of elementary particles present in a given sample of any substance. The value of Avogadro’s Number is \[{\text{6}}{\text{.023}} \times {\text{1}}{{\text{0}}^{23}}\] atoms or molecules per mole.

Complete step by step solution:
In this question, we are given the mass of neon \[{\text{w = 60g}}\].
As we know that the atomic mass of neon is 20. It is a noble gas that has a stable electronic configuration.
So, moles of a substance is defined as the ratio of the mass of a substance to that of its molecular or atomic mass.
\[
  moles = \dfrac{{Mass{\text{ }}of{\text{ }}subs\tan ce}}{{Molecular{\text{ }}mass}} \\
  moles = \dfrac{{60}}{{20}} = 3 \\
  \]
1 mole of a substance contains \[{\text{6}}{\text{.023}} \times {\text{1}}{{\text{0}}^{23}}\] atoms.
So, 3 moles of neon contain \[3 \times {\text{6}}{\text{.023}} \times {\text{1}}{{\text{0}}^{23}}\] number of atoms.
So \[{\text{60g}}\] of neon contains \[3 \times {\text{6}}{\text{.023}} \times {\text{1}}{{\text{0}}^{23}}\] number of atoms.

Hence the correct option is (D).

Note: Molality and molarity are two different concepts. Molality is basically the ratio of the number of moles of the substance to the total volume of the solution. On the other hand, molality is represented as the ratio of the number of moles of the substance to the total mass of the solvent. Both these quantities are extremely useful while solving questions related to substance concentrations.