A sample of a compound of xenon and fluorine contains molecules of a single type; XeFn, where n is a whole number. If 5.0 x 1020 of these XeFn molecules have a mass of 0.172 g, what is the value of n?

Avogadro’s number represent the number of the constituent particles which are present in one mole of the substance. It is named after scientist Amedeo Avogadro and is denoted by [tex]N_0[/tex].

Also, it is the number of particles in exactly 12.000 g of isotope carbon 12.

Avogadro constant:-

[tex]N_a=6.023\times 10^{23}[/tex]

Hence,

Mass of [tex]XeF_n[/tex] = 131.293+ n18.998 g

So,

[tex]6.023\times 10^{23}[/tex] molecules have a mass of 131.293+ n18.998 g

Also,

[tex]1[/tex] molecules have a mass of [tex]\frac{(131.293+ n18.998)}{6.023\times 10^{23}}[/tex] g

So,

[tex]5.0\times 10^{20}[/tex] molecules have a mass of [tex]\frac{(131.293+ n18.998)}{6.023\times 10^{23}}\times 5.0\times 10^{20}[/tex] g

Also, given mass = 0.172 g

Thus,

[tex]\frac{(131.293+ n18.998)}{6.023\times 10^{23}}\times 5.0\times 10^{20}=0.172[/tex]

[tex]\frac{18.998n+131.293}{1204.6}=0.172[/tex]

[tex]18.998n+131.293=207.1912[/tex]

[tex]n=\frac{75.8982}{18.998}=4[/tex]

Thus, value of n is 4.