Question 34 of 36advanced🔧 ApplyNumerical5 marks
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 (i) empirical formula, (ii) molar mass of the gas, and (iii) molecular formula.
(i)
Answer
Empirical formula is CH
(ii)
Answer
Molar mass of the gas is 26 g/mol
(iii)
Answer
Molecular formula is C2H2
Explanation
To find the empirical formula, the moles of carbon and hydrogen are determined from the masses of CO2 and H2O produced during combustion. The molar mass is found using the mass-volume relationship at STP. Finally, the molecular formula is obtained by dividing the molar mass by the empirical formula mass to find the multiplier 'n'.