Question

An oxide of phosphorus has an Mr value of 220. It is 56.4% phosphorus. Find its molecular formula. ( Ar of phosphorus,31)

Answer 1

the oxide has a 100%

Phosphorus has a 56.4% , oxygen has a percent of 100-56.4 = 43.6%

the moles of Phosphorus =$56.14/ 30.97 = 1.81$

the moles of Oxygen =$43.6/16.0 =2.725$

moles of P : O 1.81: 2.725

mole ratio P: O $(1.81/1.81) = 1$ O $(2.725/1.81) = 1.5$

Mole ratio P : O = 1 : 1.5 to get rid of the decimal we multiply by 2.

mole ratio = 1 : 3

formula of oxide of Phosphorus = PO₃