Answer:
[tex]15.7\cdot 10^{23}[/tex]
Explanation:
In order to solve this problem, we have to find the number of moles of NaCl first.
The number of moles of NaCl is given by:
[tex]n=\frac{m}{M}[/tex]
where:
m = 75.9 g is the mass of the sample of NaCl in this problem
[tex]M=58.4 g/mol[/tex] is the molar mass of NaCl, that is the amount of mass contained in 1 mole of the substance
Therefore, we have
[tex]n=\frac{75.9}{58.4}=1.30 mol[/tex]
We also know that 1 mole of a substance contains always a number of molecules equal to the Avogadro number:
[tex]N_A=6.022\cdot 10^{23}[/tex]
So, since here we have 1.30 moles, the number of molecules in this sample of NaCl is:
[tex]N=nN_A=(1.30)(6.022\cdot 10^{23})=7.83\cdot 10^{23}[/tex]
However, here we are asked how many atoms the sample contains. Since 1 molecule of NaCl contains 2 atoms (1 atom of Na and 1 atom of Cl), it means that the number of atoms in this sample is twice the number of molecules, so:
[tex]N' = 2N=2(7.83\cdot 10^{23})=15.7\cdot 10^{23}[/tex]
