Question

a given sample of a xenon fluoride compound contains a molecules of type XeF(sub)n, where n is a whole number Given that 9.03X10 ^20 molecules of XeFn weighs 0.311g, determine that the value of n in the formula

Answer 1

We know that 1 mole of any compound contains avagadro number(6.023x10²³) of molecules

Molar mass of XeFn is = [131.3 + (n x 19) ] g/mol

So (131.3 + 19n) g of XeF_n contains 6.023x10²³ molecules

M g of XeF_n contains 9.03x10²⁰ molecules

M = [( 9.03x10²⁰ x (131.3 +19n)] / (6.023x10²³ )

    = 1.5x10^-3 x (131.3+19n)
But given that 9.03X10 ²⁰ molecules of XeF_n weighs 0.311g that means M = 0.311 g

M = 1.5x10^-3 x (131.3+19n) = 0.311

     (131.3+19n) = 0.311 / (1.5x10^-3 )

                         = 207.4

                  19n = 207.4 -131.3

                         = 76.1

                      n = 4

So the value of n = 4 & the formula is XeF₄