Question

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 dioxidegas and water vapor. Calculate the moles of acetylene needed to produce 2.40 mol of water. Be sure your answer has a unit symbol, if necessary, and round it to 3 significant digits.

Answer 1

2.40 mol C₂H₂

Procedure

The first step is to state the chemical reaction given

C₂H₂ + O₂ → CO₂ + H₂O

Then we will proceed to balance the equation by using the trial and error method

2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O

After balancing the equation, we use the reaction stoichiometry to find the moles of acetylene needed to produce 2.40 moles of water, assuming oxygen is in excess.

`2.40\text{ mol H}_2\text{O}\frac{2\text{ mol C}_2\text{H}_2}{2\text{ mol H}_2\text{O}}=2.40\text{ mol C}_2\text{H}_2`