Chapter 19, Problem 55R

To determine

To calculate: The mass of the oxygen.

Answer to Problem 55R

The mass of Oxygen is 16 g.

Explanation of Solution

Given info:

The Masses of the sodium and sodium oxide are 46 g and 62 g respectively.

Formula used:

The number of moles is given as,

  $\text{Number}\text{of}\text{moles}\text{=}\frac{\text{mass}\text{of}\text{substance}}{\text{molar}\text{mass}}$

Calculation:

The reaction of sodium and oxygen to form sodium oxide is represented as follows:

  $\text{Na}+{\text{O}}_{\text{2}}\to {\text{Na}}_{\text{2}}\text{O}$

The above reaction can be balanced as follows:

  $\text{4Na}+{\text{O}}_{\text{2}}\to 2{\text{Na}}_{\text{2}}\text{O}$

Since, the above reaction is balanced, it follows the law of conservation of mass. The total mass of reactant should be equal to the product.

The total mass of reactant will be sum of mass of sodium and oxygen.

  $\mathrm{M}=46\text{ g}+{\mathrm{m}}_{{\text{O}}_{\text{2}}}$

The total mass of product is 62 g that is mass of sodium oxide.

Thus,

  $\begin{array}{c}62=46+{\mathrm{m}}_{{\text{O}}_{\text{2}}}\\ {\mathrm{m}}_{{\text{O}}_{\text{2}}}=\left(62-46\right)\text{ g}\\ =16\text{ g}\end{array}$

Conclusion:

Thus, mass of oxygen gas is 16 g.