Acetylene (C2H2) gas is often used in welding torches because of the very high heat produced when it reacts with oxygen (O2) gas, producing carbon dioxide gas and water vapor. Calculate the moles of acetylene needed to produce 0.090mol of carbon dioxide. Be sure your answer has a unit symbol, if necessary, and round it to 2 significant digits.

According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products must be same as the mass of reactants. For the conservation of mass, the number of atoms of each element must be same in reactants and products. Thus we need to balance the reaction by writing appropriate stochiometric coefficients.

The balanced chemical reaction for combustion of acetylene is

[tex]2C_2H_2+5O_2\rightarrow 4CO_2+2H_2O[/tex]

According to stoichiometry:

4 moles of carbon dioxide are produced by = 2 moles of acetylene

Thus 0.090 moles of carbon dioxide are produced by = [tex]\frac{2}{4}\times 0.090=0.045[/tex] moles of acetylene

Thus the moles of acetylene needed to produce 0.090mol of carbon dioxideare 0.045 mol