Question

A sample of $O_2$ gas is collected over water at $23 ^{\circ}C$ at a barometric pressure of $751\, mm\, Hg$ (vapour pressure of water at $23^{\circ}C$ is $21\, mm\, Hg$).The partial pressure of $O_2$ gas in the sample collected is

• A. 21 mm Hg
• B. 751 mm Hg
• C. 0.96 atm
• D. 1.02 atm

Answer 1

Answer: (C)

0.96 atm

Answer 2

Using the Dalton's law P (Total) = Poxygen +Pwater The vapor pressure of water is $21\, mmHg$ $751\, mmHg =$ Poxygen $+21\, mmHg$ Poxygen $=751\, mmHg -21\, mmHg$ Poxygen $=730\, mmHg$ Convert the partial pressure of oxygen in to atmosphere $(730\, mmHg )(1 atm / 760\, mmHg )=0.96\, atm$