Question

A compound has been found to be 49.18% phosphorus and 50.82% oxygen by mass. What is the empirical formula of the compound?

Answer 1

The atomic weights of phosphorous and oxygen are 31 and 16 respectively.

The compound has 49.18% phosphorous by mass i.e. (49.18/31)% by number. Which is equal to 1.5486% by number.

And the compound has 50.82% oxygen by mass i.e. (50.82/16)% by number. Which is equal to 3.176% by number.

Therefore, the empirical formula of the compound would be P_(1.5486)O_(3.176).

If we take the round figure then it becomes P_1.5O_3.

One of value is fraction, so the value is multified by 2 to have the integer value. [1.5x2=3 and 3x2=6]

Now the final empirical formula results P₃O₆.