Question

Complete combustion of 3.10 g of a hydrocarbon produced 9.96 g of CO2 and 3.40 g of H2O. What is the empirical formula for the hydrocarbon?

C?H?

my answer was C2H3, but it is wrong

insert subscripts as necessary

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

= 9.96/44

= 0.2264

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

= 3.4/18

= 0.1889

Since 1 mol of CO2 has 1 mol of C

Number of moles of C in CO2= 0.2264

so, x = 0.2264

Since 1 mol of H2O has 2 mol of H

Number of moles of H = 2*0.1889 = 0.3778

Divide by smallest:

C: 0.2264/0.2264 = 1

H: 0.3778/0.2264 = 1.67 = 5/3

Multiply by 3 to get simplest whole number ratio:

C: 1*3 = 3

H: 5/3 * 3 = 5

So empirical formula is:C3H5

Answer: C3H5