Chapter 3, Problem 46QAP

Sodium borate decahydrate, ${\text{Na}}_{\text{2}}{\text{B}}_{\text{4}}{\text{O}}_{\text{7}}\cdot \text{1}0{\text{H}}_{\text{2}}\text{O}$ is commonly known as borax. It is used as a deodorizer and mold inhibitor. A sample weighing 15.86 g is heated until a constant mass is obtained indicating that all the water has been evaporated off.

(a) What percent, by mass of ${\text{Na}}_{\text{2}}{\text{B}}_{\text{4}}{\text{O}}_{\text{7}}\cdot \text{1}0{\text{H}}_{\text{2}}\text{O}$ is water?

(b) What is the mass of the anhydrous sodium borate, Na₂B₄O₇?