Question

Complete combustion of 2.10 g of a hydrocarbon produced 6.83 g of CO2 and 2.10 g of H2O. What is the empirical formula for the hydrocarbon?

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

= 6.83/44

= 0.155227

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

= 2.1/18

= 0.116667

Since 1 mol of CO2 has 1 mol of C

Number of moles of C in CO2= 0.155

so, x = 0.155227

Since 1 mol of H2O has 2 mol of H

Number of moles of H = 2*0.116667 = 0.233

Divide by smallest to get simplest whole number ratio:

C: 0.155/0.155 = 1

H: 0.233/0.155 = 1.5

multiply both by 2

C: 1*2=2

H: 1.5*2 = 3

So empirical formula is:C2H3