Question

Calculate following in \[5.6g\] of \[nitrogen\]
A. Number of moles
B. Number of molecules of \[{N_2}\]
C. Number of atoms of \[nitrogen\]

Answer 1

Hint: To find the above all solutions, one must be familiar with the concept of moles. The above quantity is the provided or given mass of the element\[nitrogen\]. Simply putting that value in the number of moles formula, we will be able to find the solution.

Complete answer:
One mole is the amount of a substance that contains as many particles or entities as there are atoms in exactly \[12g\] of the \[^{12}C\] isotopes. It is similar to the quantities as we denote one dozen or a gross for \[12\] or \[144\] items. The S.I. unit is \[mole\] and the symbol for mole is \[mol\]. The mole of a substance always contains the same number of entities, no matter what the substance may be. This is represented by which is equal to \[6.022 \times {10^{23}}atoms/mol\]
Also the molar mass is the mass of one mole of a substance in \[grams\]. The molar mass in \[grams\] is numerically equal to atomic or molecular formula mass in \[u\]
The number of moles is given by the formula-
\[No.{\text{ }}of{\text{ }}moles = \dfrac{{Given{\text{ mass}}}}{{Molar{\text{ mass}}}}\]
Now that we are familiar with these concepts we will solve the given question.
A. To find the number of moles of \[nitrogen\] atom we will use the same formula-
\[No.{\text{ }}of{\text{ }}moles = \dfrac{{Given{\text{ mass}}}}{{Molar{\text{ mass}}}}\]
Molar mass of \[{N_2}\]= \[2 \times 14 = 28g/mol\]
No. of moles= \[\dfrac{{5.6}}{{28}} = 0.2mol\]
B. Number of molecules of \[{N_2}\]
\[ = 6.022 \times {10^{23}} \times no.{\text{ of moles of }}{N_2}\]
\[ = 6.022 \times {10^{23}} \times 0.2\]
\[ = 1.2 \times {10^{23}}\]
C. Number of atoms of \[{N_2}\]
(There are two \[nitrogen\] atoms in \[{N_2}\])
\[ = 2 \times {\text{no}}{\text{. of }}{{\text{N}}_2}{\text{ molecules}}\]
\[ = 2 \times 1.2 \times {10^{23}} = 2.4 \times {10^{23}}\]

Note:
Atoms and molecules are extremely small in size and their numbers in even a small amount of any substance is really very large. To handle such large numbers, a unit of similar magnitude is required. Therefore the mole concept was introduced.