When 0.422g of phosphorus is burned, 0.967g of a white oxide is obtained.
a. determine the empirical formula of the oxide
b. write a balanced equation for the reaction of phosphorus and molecular oxygen on the basis of this empirical formula

Answer :

(a) The empirical formula of a compound is,

(b) The balanced chemical equation will be:

Solution :  Given,

Mass of phosphorus = 0.422 g

Mass of white oxide = 0.967 g

Molar mass of phosphorus = 31 g/mole

Molar mass of oxygen = 16 g/mole

First we have to calculate the mass of oxygen.

Mass of oxygen = Mass of white oxide - Mass of phosphorus

Mass of oxygen = 0.967 - 0.422

Mass of oxygen = 0.545 g

Now convert given masses into moles.

Moles of P =

Moles of O =

For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For P =

For O =

The ratio of P : O = 1 : 2.5

To make this ratio in a whole number we multiple ratio by 2, we get:

The ratio of P : O = 2 : 5

The mole ratio of the element is represented by subscripts in empirical formula.

The Empirical formula =

The balanced chemical equation will be: