Question

A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives 3.38 g carbon dioxide , 0.690 g of water and no other products. A volume of 10.0 L (measured at STP) of this welding gas is found to weigh 11.6 g. Calculate empirical formula

Answer 1

CxHy + O2 ==> CO2 + H2O

Here, moles of C:  3.38 g CO2 x 1 mole CO2/44 g x 1 mole C/mole CO2

                                            = 0.0768 moles of C

And moles of H:  0.690 g H2O x 1 mole H2O/18 g x 2 moles H/mole H2O

                                          = 0.0767 moles of H

Since the mole ratio of C: H is 1:1,

So, the empirical formula is CH.