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 oxygen needed to produce 0.085mol of carbon dioxide. Be sure your answer has a unit symbol, if necessary, and round it to 2 significant digits.

The correct answer is 0.11 mol O₂

Explanation:

The chemical equation for the reaction of acetylene (C₂H₂) with O₂ to produce carbon dioxide (CO₂) and water (H₂O) is the following:

2 C₂H₂(g) + 5 O₂(g) → 4 CO₂(g) + 2 H₂O(g)

The chemical equation is balanced : with the proper estequiometrical coefficients. According to this, 2 moles of C₂H₂ reacts with 5 moles of O₂ to give 4 moles of CO₂ and 2 moles of H₂O.

In order to calculate how many moles of O₂ are needed to produce 0.085 moles of CO₂, we multiply the 0.085 moles of CO₂ by the factor 5 moles O₂/4 moles CO₂ (because 4 moles of CO₂ are produced by 5 moles of O₂ according to the chemical equation):

0.085 moles CO₂ x (5 moles O₂/4 moles CO₂) = 0.10625 moles O₂ = 0.11 moles O₂

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