Chapter 9, Problem 55A

Interpretation Introduction

Interpretation:

The mass of oxygen gas required for complete combustion of 150 g of acetylene should be determined.

Concept Introduction:

Mole is the amount of the substance that contains the same number of particles or atoms or molecules. Molar mass is defined as an average mass of atoms present in the chemical formula. It is the sum of the atomic masses of all the atoms present in the chemical formula of any compound.

Answer to Problem 55A

460.8 g of oxygen is needed for the complete combustion of acetylene.

Explanation of Solution

The combustion reaction is shown below:

  ${\text{2C}}_{\text{2}}{\text{H}}_{\text{2}}\left(\text{g}\right)\text{+}{\text{5O}}_{\text{2}}\left(\text{g}\right)\to {\text{4CO}}_{\text{2}}\left(\text{aq}\right)\text{+}{\text{2H}}_{\text{2}}\text{O}\left(\text{g}\right)$

Given information:

Mass of acetylene = 150 g

Molar mass of acetylene = 26.04 gmol-1

The calculation of moles is shown below:

  $\begin{array}{c}\text{moles}\text{of}\text{acetylene}\text{=}\frac{\text{mass}\text{of}\text{acetylene}}{\text{molar}\text{mass}\text{of}\text{acetylene}}\\ \text{=}\frac{\text{150}\text{g}}{\text{26}\text{.04}{\text{gmol}}^{\text{-1}}}\\ \text{=}\text{5}\text{.76}\text{mol}\end{array}$

According to the combustion reaction; 2 moles of acetylene reacts with 5 moles of O₂ which produced 4 moles of CO₂and 2 moles of H₂O

  $\begin{array}{l}\text{2 moles of acetylene = 5 moles of oxygen}\hfill \\ \begin{array}{l}\text{5}\text{.76 mol of acetylene =}\frac{\text{5}\text{.76}}{\text{2}}\text{×}\text{5}\text{moles}\text{of}\text{oxygen}\\ \text{=}\text{14}\text{.4}\text{moles}\text{of}\text{oxygen}\end{array}\hfill \end{array}$

Conversion of moles into mass is shown below:

  $\begin{array}{c}\text{moles}\text{of}{\text{O}}_{\text{2}}\text{=}\frac{\text{mass}\text{of}{\text{O}}_{\text{2}}}{\text{molar}\text{mass}\text{of}{\text{O}}_{\text{2}}}\\ \text{mass}\text{of}{\text{O}}_{\text{2}}\text{=}\text{14}\text{.4}\text{mol}\text{×}\text{32}{\text{gmol}}^{\text{-1}}\\ \text{=}\text{460}\text{.8}\text{g}\end{array}$

Conclusion

460.8 g of oxygen is needed for the complete combustion of acetylene.