Question

If the atomic mass is $ 23 $ , then the number of moles in $ 46g $ of sodium is:
 $ A. $ $ 1 $
 $ B. $ $ 2 $
 $ C. $ $ 2.3 $
 $ D. $ $ 4.6 $

Answer 1

Hint: Mathematically, number of moles is defined as the mass of an element or compound divided by molar mass of that element or compound. Unit of number of moles is $ mol $ . One mole of any substance is equal to the Avogadro number.

Formula used: Number of moles $ = \dfrac{{mass}}{{molarmass}} $

Complete step by step solution
In the given we have given that atomic mass is $ 23 $ mass of sodium is $ 46g $ . We have to determine the number of moles. We can calculate the number of moles by using the relation between number of moles, atomic mass and mass.
Since, we know
Number of moles $ = \dfrac{{mass}}{{molarmass}} $
Now, we have mass and atomic mass in the given question $ 46 $ and $ 23 $ respectively. So, we can calculate using the above relation, we get number of moles
Number of moles $ = \dfrac{{46}}{{23}} = 2 $
Thus we get a number of moles $ 2 $ . So, the correct option is $ B. $
Additional information: Atomic mass: It is defined as the mass of an atom of a particular substance. It is also defined as the total number of neutrons and protons present in an atom known as atomic mass. For example let us consider an atom namely sodium which has $ 12 $ protons and $ 13 $ neutron are present in it. Hence the atomic mass of sodium is $ 23 $ .

Note:
A mole is defined as $ 6.02214 \times {10^{23}} $ of some chemical unit, be it atoms, molecules, ion, or other. The mole is a convenient unit to use because of the great number of atoms, molecules or other in any substance. The mole was originally defined as the number of atoms in $ 12gram $ of carbon- $ 12 $ .