Chapter 5, Problem 71E

The nitrogen content of organic compounds can be determinedby the Dumas method. The compound in questionis first reacted by passage over hot CuO(s):

$\text{Compound}\underset{\text{CuO}\left(s\right)}{\overset{\text{Hot}}{\to }}{\text{N}}_{\text{2}}\text{(}g{\text{)+CO}}_{\text{2}}\text{(}g{\text{)+H}}_{\text{2}}\text{O(}g\text{)}$

The gaseous products are then passed through a concentratedsolution of KOH to remove the ${\text{CO}}_{\text{2}}$ . After passagethrough the KOH solution, the gas contains ${\text{N}}_{\text{2}}$ andis saturated with water vapor. In a given experiment, a0.253-g sample of a compound produced 31.8 mL of ${\text{N}}_{\text{2}}$ saturated with water vapor at 25°C and 726 torr. Whatis the mass percent of nitrogen in the compound? (Thevapor pressure of water at 25°C is 23.8 torr.)