Question

A 0.100 g sample of a compound containing only C and H is burned in excess oxygen, producing 0.338 g of CO2 and 0.0692 g of H2O. What is the empirical formula of the compound?

Answer 1

To calculate empirical formula we must know the mass of C, H .

Lets find out the moles of C and H.

Mass of C are formed from CO2 and for H we can get it from H2O

Mass ratio between CO2 and C is 44.009 : 12.011

Calculation of mass of C by using 0.338 g of CO2

Mass of C in = 0.338 g CO2 x 12.011 g C / 044.009 g CO2

= 0.092247 g

Therefore mass of H = 0.100 g sample – mass of C = 0.100 g sample – 0.092247 g C = 0.007753 g

Calculation of moles of each

Mol C = 0.092247 g C / Molar mass of C = 0.092247 g / 12.011 g per mol C = 0.00768 mol = 0.0077

Mol of H = 0.007753 g /1.008 g per mol = 0.077

Calculation of simple whole number ratio

Their mole show that both are in same ratio

Therefor the mole ratio would be C : H and empirical formula is CH