Chapter 9, Problem 54A

Interpretation Introduction

Interpretation:

The mass of oxygen gas should be predicted.

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 54A

Mass of O₂ = 1.34 g

Explanation of Solution

The given reaction is shown below:

  ${\text{Na}}_{\text{2}}{\text{O}}_{\text{2}}\left(\text{s}\right)\text{+}{\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)\to \text{NaOH}\left(\text{aq}\right)\text{+}{\text{O}}_{\text{2}}\left(\text{g}\right)$

Given information:

Mass of sodium peroxide = 3.25 g

Molar mass of sodium peroxide = 77.98 gmol-1

The calculation of moles is shown below:

  $\begin{array}{c}\text{moles}\text{of}{\text{Na}}_{\text{2}}{\text{O}}_{\text{2}}\text{=}\frac{\text{mass}\text{of}{\text{Na}}_{\text{2}}{\text{O}}_{\text{2}}}{\text{molar}\text{mass}\text{of}{\text{Na}}_{\text{2}}{\text{O}}_{\text{2}}}\\ \text{=}\frac{\text{3}\text{.25}\text{g}}{\text{77}\text{.98}{\text{gmol}}^{\text{-1}}}\\ \text{=}\text{0}\text{.042}\text{mol}\end{array}$

The calculation of mass of O₂ is shown below:

  $\begin{array}{c}\text{0}\text{.042}\text{mol}{\text{Na}}_{\text{2}}{\text{O}}_{\text{2}}\text{×}\left(\frac{\text{1}\text{mol}{\text{O}}_{\text{2}}}{\text{1}\text{mol}{\text{Na}}_{\text{2}}{\text{O}}_{\text{2}}}\right)\text{×}\text{32}{\text{gmol}}^{\text{-1}}{\text{O}}_{\text{2}}\\ \text{=}\text{1}\text{.34}\text{g}\text{of}{\text{O}}_{\text{2}}\end{array}$

Conclusion

Mass of O₂ = 1.34 g