a given sample of xenon flouride contains molecules of a single tyoe XeFn, where n is some whole number.?

Question

Given that 9.09e20 molecules of XeFn weigh 0.311g, calculate n.

Answer 1

First convert to moles by dividing by Avogadro's number,

N = 9.09 * 10^20 / 6.02 * 10^23 = 0.001510 mole

The molar mass of your substance is therefore

M = m / N = 0.311 / 0.001510 = 206.0 amu

Xe has mas 131.3, so for the fluor you have lef

206.0 - 131.3 = 74.66 amu

Each fluor contributes 19.0 amu, so we find

n = 74.66 / 19.0 = 3.93 ~ 4

The substance is therefore XeF4, xenon tetrafluoride.