if the molar mass of a binary molecule is between 215 and 225 amus, contains 43.64% O, the balace P...?

Question

what is the molecular formula

Answer 1

This should really have been asked in Chemistry, but never mind.

OK, #amus of O is between 43.64%(215) = 93.8 and 43.64%(225) = 98.2. So the number of O atoms is between 93.8/16.00 = 5.86 and 98.2/16.00 = 6.14, so it must be 6.

So there are 6*16.00 = 96.00 amus of O; since this is 43.64% of the total, the total must be 96.00/0.4364 = 220.0 amus, meaning that there are 220.0 - 96.00 = 124.0 amus of P. The number of P atoms is therefore 124.0/31.0 = 4, so the molecular formula is P4O6.