The number of atoms N = 5.8 x 10²¹
Further explanation
A mole is a unit of many particles (atoms, molecules, ions) where 1 mole is the number of particles contained in a substance that is the same amount as many atoms in 12 gr C-12
1 mole = 6.02.10²³ particles
mass of N in 0.82 g of NaNO₃ (MW NaNO₃: 85 g/mol) :
[tex]\tt mass~N=\dfrac{Ar~N}{MW~NaNO_3}\times mass~NaNO_3\\\\mass~N=\dfrac{14}{85}\times 0.82\\\\mass~N=0.135~g[/tex]
moles of N :
[tex]\tt mol=\dfrac{mass}{Ar}\\\\mol=\dfrac{0.135}{14}=0.0096[/tex]
The number of atoms N :
[tex]\tt N=n\times No\\\\N=0.0096\times 6.02\times 10^{23}\\\\N=5.8\times 10^{21}~atoms[/tex]
