Question

Prior to their phaseout in the 1980s, chemicals containing lead were commonly added to gasoline as anti-knocking agents. A 1.671 g sample of one such additive containing only lead, carbon, and hydrogen was burned in an oxygen rich environment. The products of the combustion were 1.819 g of CO2(g) and 0.9306 g of H2O(g). Insert subscripts below to appropriately display the empirical formula of the gasoline additive:

Answer 1

Number of moles of CO2 = 1.819 / 44.00964 = 0.041 moles

0.041 moles of C = 0.041 x 12.01078 = 0.492 grams

Number of moles of water = 0.93016 / 18.01532 = 0.0516 moles

Amount of hydrogen = 0.0516 x 2 x 1.007947 = 0.104 g

Amount of lead in the sample = 1.671 - (0.492 + 0.104)

= 1.075 g

Number of moles of Pb = 1.075 / 207.21 = 0.0052 moles

Dividing the number of moles by a common value to get the ratio of atoms as : 8:20:1

So the empirical formula of the compound will be : C₈H₂₀Pb