A 5.00 L flask contains 0.02 moles oxygen at 22°C, what is its pressure, in kilopascals? What is the pressure in atm?

1 Answer
Aug 6, 2016

The pressure of the gas is 10 kPa or 0.1 atm.

This looks like the time to apply the Ideal Gas Law:

#color(blue)(|bar(ul(PV = nRT)|)#,

where

  • #P# is the pressure
  • #V# is the volume
  • #n# is the number of moles
  • #R# is the gas constant
  • #T# is the temperature

We can rearrange the Ideal Gas Law to get

#P = (nRT)/V#

#n = "0.02 mol"#
#R = "8.314 kPa·L·K"^"-1""mol"^"-1"#
#T = "(22 + 273.15) K" = "295.15 K"#
#V = "5.00 L"#

#P = (nRT)/V = (0.02 color(red)(cancel(color(black)("mol"))) × "8.314 kPa·" color(red)(cancel(color(black)("L·K"^"-1""mol"^"-1"))) × 295.15 color(red)(cancel(color(black)("K"))))/(5.00 color(red)(cancel(color(black)("L")))) = "10 kPa"#

To calculate the pressure in atmospheres, repeat the calculation using the value

#R = "0.082 06 L"·"atm"·"K"^"-1""mol"^"-1"#

#P = (nRT)/V = (0.02 color(red)(cancel(color(black)("mol"))) × "0.082 06 L·" color(red)(cancel(color(black)("atm"·"K"^"-1""mol"^"-1"))) × 295.15 color(red)(cancel(color(black)("K"))))/(5.00 color(red)(cancel(color(black)("L")))) = "0.1 atm"#