Question

Consider a 5.5−gram sample of each of the substances F2, SF2, or CF4. Which sample contains the greatest number of molecules?

Answer 1

let us solve it using mol concept .
1 mol of atoms/ions/molecules contains avogadro number [6.022 x10^23 number]
of particles

so covert each substances in to moles . The one with more number of moles will
have greatest number of molecules.

given
mass of F2 = 5.5 g
molar mass of F2=38 g/mol
moles of F2 present = mass of F2/molar mass of F2
= 5.5 g/38 g/mol = 0.145 mols

mass of SF2 = 5.5 g
molar mass of SF2=70.06g/mol
moles of SF2 present = mass of SF2/molar mass of SF2
= 5.5 g/70.06g/mol = 0.0.0785 mols

mass of CF4 = 5.5 g
molar mass of CF4=88.00 g/mol
moles of F2 present = mass of F2/molar mass of CF4
= 5.5 g/88.00g/mol = 0.0625 mols

Thus mols of F2 is is highest compared to SF2 and CF4. Hence 5.5 g of
F2 will contain greatest number of molecules