Question

Upon combustion, a compound containing only carbon and hydrogen produces 1.62 gCO2 and 0.884 gH2O. Find the empirical formula of the compound.

I have found that CO2= .036809816 and H2O= .0490566038 but I dont know where to go from this point

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

= 1.62/44

= 3.682*10^-2

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

= 0.884/18

= 4.911*10^-2

Since 1 mol of CO2 has 1 mol of C

Number of moles of C in CO2= 3.682*10^-2

so, x = 3.682*10^-2

Since 1 mol of H2O has 2 mol of H

Number of moles of H = 2*4.911*10^-2 = 9.822*10^-2

Divide by smallest:

C: 3.682*10^-2/3.682*10^-2 = 1

H: 9.822*10^-2/3.682*10^-2 = 8/3

Multiply by 3 to get simplest whole number ratio:

C: 1*3 = 3

H: 2.67*3 = 8

So empirical formula is:C3H8

Answer: C₃H₈