Question

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

Answer 1

The question is incomplete. The complete question is :

Acetylene $C_2H_2$ gas is often used in welding torches because of the very high heat produced when it reacts with oxygen $O_2$ gas, producing carbon dioxide gas and water vapor. Calculate the moles of oxygen needed to produce 1.5 mol of carbon dioxide. Be sure your answer has a unit symbol, if necessary, and round it to the correct number of significant digits.

Answer: 1.9 moles of oxygen are needed to produce 1.5 moles of carbon dioxide.

Explanation:

According to the law of conservation of mass, mass can neither be created nor be destroyed. Thus the mass of products has to be equal to the mass of reactants. The number of atoms of each element has to be same on reactant and product side. Thus chemical equations are balanced.

The balanced reaction for combustion of acetylene is:

$2C_2H_2+5O_2\rightarrow 4CO_2+2H_2O$

According to stoichiometry;

4 moles of carbon dioxide are produced by = 5 moles of oxygen

Thus 1.5 moles of carbon dioxide are produced by =$\frac{5}{4}\times 1.5=1.9$ moles of oxygen

Thus 1.9 moles of oxygen are needed to produce 1.5 moles of carbon dioxide.