Prior to their phaseout in the 1980s, chemicals containing lead were commonly added to gasoline as anti‑knocking agents. a 6.897g sample of one such additive containing only lead, carbon, and hydrogen was burned in an oxygen‑rich environment. the products of the combustion were 7.5 g co2(g) and 3.841 g h2o(g).

determine the empirical formula of the gasoline additive.

Empirical formula is C8H20Pb

Explanation:

Mass of C = molar mass of C/molar mass of CO2 x mass of CO2

= 12.01/44.01 x 5.027

= 1.372 g

Mass of H = 2 x molar mass of H/molar mass of H2O x mass of H2O  

= 2 x 1.008/18.02 x 2.572

= 0.288 g

Mass of Pb = mass of sample - mass of C - mass of H

= 4.617 - 1.372 - 0.288

= 2.957 g  

Since moles = mass/molar mass

Moles of C : H : Pb = 1.372/12.01 : 0.288/1.008 : 2.957/207.21

= 0.1142 : 0.2857 : 0.01427

= 8 : 20 : 1

Empirical formula is C8H20Pb