Question

A 5.00 gram sample of an oxide of lead PbxOy contains 4.33 g of lead. Determine simplest formula for the compund

Answer 1

Answer: The empirical formula is
`PbO_2`

Step-by-step explanation:

Mass of Pb = 4.33 g

Mass of O = (5.00-4.33) g = 0.67 g

Step 1 : convert given masses into moles

Moles of Pb =
`\frac{\text{ given mass of Pb}}{\text{ molar mass of Pb}}= (4.33g)/(207g/mole)=0.021moles`

Moles of O =
`\frac{\text{ given mass of O}}{\text{ molar mass of O}}= (0.67g)/(16g/mole)=0.042moles`

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

For Pb =
`(0.021)/(0.021)=1`

For O =
`(0.042)/(0.021)=2`

The ratio of Pb O= 1: 2

Hence the empirical formula is
`PbO_2`