Question

0.04 g of magnesium was put into the bottom of the tube containing a dilute solution of $HCl$ and it reacted completely and formed hydrogen gas and the following data was recorded:
Air pressure in the room = 730 mm Hg
Temperature of the water solution = 302 K
Vapor pressure of water at 302 K = 30 mm Hg
Eudiometer was not fully filled by the gas collected and the height of the meniscus above the level of the water was 40.8 mm.
After correction for the vapor pressure of the water, pressure of the collected gas is :

• A. 730 mm Hg
• B. 727 mm Hg
• C. 30.0 mm Hg
• D. 697 mm Hg
• E. 760 mm Hg

Answer 1

Answer: (D)

697 mm Hg

After correction for the vapor pressure of the water, pressure of the collected gas$=730-3-30.0=697$ mm Hg.
Note: Here, 730 mm Hg is the air pressure in room, 3 mm Hg is the correction required as the height of the meniscus above the level of the water was 40.8 mm. 30.0 mm Hg is the vapour pressure of water.