Prior to their phaseout in the 1980s, chemicals containing lead were commonly ad

Question

Prior to their phaseout in the 1980s, chemicals containing lead were commonly added to gasoline as anti-knocking agents. A sample of 8.907 g of gasoline containing only lead, carbon and hydrogen was burned completely in an oxygen rich environment. The products collected from the combustion reaction were 9.695 g of CO2 and 4.961 g of H20 (6 pts) a) Calculate both the moles and the grams of C and H found in the reaction products 1. (2 pts) Using the gram amounts of C and H calculated above, determine the amount of lead in the gas reactant, in grams, and convert this to moles. (2 pts) b) Use the molar amounts found in parts a and b to arrive at the empirical formula for the gasoline compound. (2 pts) c) More Practice (optional A 4.24-gg sample of a carboxylic acid (composed of only C,H, and 0) is burned. The reaction produces 6.21 g of carbon dioxide and 2.54 g of water. The compound was found to have a molar mass of 180 g/mol in a separate experiment. What is the molecular formula of the compound?

Explanation / Answer

Ans 1

Part a

Mass of CO2 = 9.695 g

Moles of CO2 = mass/molecular weight

= 9.695 g / 44g/mol

= 0.22 mol

Moles of C = 0.22 mol

Mass of C = 0.22 mol x 12 g/mol = 2.64 g

Mass of H2O = 4.961 g / 18g/mol

= 0.2756 mol

Moles of H = 2 x 0.2756 = 0.5512 mol

Mass of H = 0.5512 mol x 1 g/mol = 0.5512 g

Part b

Mass of lead = total mass of gasoline - mass of C - mass of H

= 8.907 - 2.64 - 0.5512

= 5.7158 g

Moles of lead = mass/molecular weight

= 5.7158 g / 207.2g/mol

= 0.02758

Part C

Divide by lowest number of moles

C : H : Pb = (0.22/0.02758) : (0.5512/0.02758) : (0.02758/0.02758)

C : H : Pb = 8 : 20 : 1

Empirical formula = C8H20Pb

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