Hydrogen gas is generated and collected over liquid water at 25 °C
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
Hydrogen gas is generated and collected over liquid water at 25 °C. The inverted collection tube traps 750 mL of gas, and the water levels inside and outside the tube are identical. The barometric pressure in the laboratory at that moment is 765 mmHg. The vapor pressure of water at 25 °C is 23.8 mmHg.
The collected hydrogen is transferred without loss to a rigid 2.00 L flask at 298 K. Pure oxygen gas is then added to the flask until the partial pressure of oxygen reaches exactly 1.50 atm. Temperature remains at 298 K throughout the transfer and addition.
(a) Calculate the partial pressure of dry hydrogen gas in the collection tube at the moment of collection.
(b) Determine the number of moles of hydrogen transferred to the 2.00 L flask.
(c) After oxygen is added, compute the total pressure inside the 2.00 L flask.
(d) Which gas—hydrogen or oxygen—contributes the larger fraction of the total pressure in the flask? Support your answer with calculations of appropriate mole fractions.