Question

A 10.150g sample of a compound known to contain phosphorus and oxygen yields 5.717 g of oxygen. Find the empirical formula of the compound

Answer 1

Answer: The empirical formula is
`P_2O_5`

Step-by-step explanation:

Mass of O = 5.717 g

Mass of P= (10.150-5.717) g = 4.433 g

Step 1 : convert given masses into moles.

Moles of O =
`\frac{\text{ given mass of O}}{\text{ molar mass of O}}= (5.717g)/(16g/mole)=0.357moles`

Moles of P=
`\frac{\text{ given mass of P}}{\text{ molar mass of P}}= (4.433g)/(31g/mole)=0.143moles`

Step 2 : For the mole ratio, divide each value of moles by the smallest number of moles calculated.

For O =
`(0.357)/(0.143)=2.5`

For P =
`(0.143)/(0.143)=1`

The ratio is to be converted to whole number

Thus whole number ratio of O : P =
`2.5* 2:1* 2=5: 2`

Hence the empirical formula is
`P_2O_5`