Hydrogen gas is collected over water in an inverted buret.If the atmospheric pressure is 745 mm Hg,the vapor pressure of water is 18 mm Hg,and a 15.0 cm-high column of water remains in the buret,the pressure of the hydrogen gas is
A)763 mm.
B)745 mm Hg.
C)727 mm Hg.
D)less than 727 mm Hg.

Question

Quizplus · Accepted Answer

The pressure of the hydrogen gas is the atmospheric pressure minus the vapor pressure of water and the pressure due to the water column in the buret. The pressure due to the water column can be calculated using the height of the water column (15.0 cm or 150 mm) and the density of mercury compared to water. Since mercury is denser than water, the pressure exerted by the water column is less than its height in mm Hg, making the pressure of the hydrogen gas less than 727 mm Hg (745 mm Hg - 18 mm Hg = 727 mm Hg, without considering the water column's pressure).

Hydrogen Gas Is Collected Over Water in an Inverted Buret