A hydrocarbon of unknown formula C_xH_ywas submitted to combustion analysis with the following results.What is the empirical formula of the hydrocarbon?

Question

Quizplus · Accepted Answer

Using the combustion analysis data, we can determine the empirical formula by first finding the number of moles of carbon and hydrogen present in the hydrocarbon.

Moles of carbon: 
(11.1 g CO2) x (1 mol CO2/44.01 g CO2) x (1 mol C/1 mol CO2) = 0.252 mol C

Moles of hydrogen: 
(2.8 g H2O) x (1 mol H2O/18.015 g H2O) x (2 mol H/1 mol H2O) = 0.311 mol H

To simplify the mole ratios, we can divide both by the smaller value (0.252 mol C) to get:

C: 1 
H: 1.23

Since we need whole number ratios, we can multiply both by 4 to get:

C: 4 
H: 4.92

The closest whole number ratio is C4H5, which corresponds to choice B.

A Hydrocarbon of Unknown Formula CxHy was Submitted to Combustion

A Hydrocarbon of Unknown Formula C_xH_ywas Submitted to Combustion