Question

A 2.50 gram sample of hydrocarbon undergoes complete combustion to produce 8.45 [8pts] grams of CO2 and 1.73 grams of H2O. What is the empirical formula of this compound?

Answer 1

let in compound number of moles of C and H be x and y respectively

Number of moles of CO2 = mass of CO2 / molar mass CO2

= 8.45/44

= 0.192

Number of moles of H2O = mass of H2O / molar mass H2O

= 1.73/18

= 0.0961

Since 1 mol of CO2 has 1 mol of C

Number of moles of C in CO2= 0.192

so, x = 0.192

Since 1 mol of H2O has 2 mol of H

Number of moles of H = 2*0.0961 = 0.1922

Divide by smallest to get simplest whole number ratio:

C: 0.192/0.192 = 1

H: 0.1922/0.192 = 1

So empirical formula is:CH

CH