Worksheet: Vapor Pressure and Relative Humidity

In this worksheet, we will practice defining a vapor's relative humidity as the ratio of the partial pressure of the vapor to its equilibrium vapor pressure.


On a warm day when the air temperature is 30.00C, a metal can is slowly cooled by adding bits of ice to liquid water in it. Condensation first appears when the can reaches 15.00C. What is the relative humidity of the air? Given the vapor pressure of water at 15.00C is 1,705 Pa and at 30.00C is 4,243 Pa.

  • A 3 9 . 5 1 %
  • B 3 8 . 7 8 %
  • C 3 8 . 1 1 %
  • D 4 0 . 8 4 %
  • E 4 0 . 1 8 %


Air is 21% oxygen.

Find the minimum atmospheric pressure that gives a relatively safe partial pressure of oxygen of 0.16 atm.

What is the minimum pressure that gives a partial pressure of oxygen above the quickly fatal level of 0.060 atm?


Find the density of air at a pressure of 1.00 atm and a temperature of 20.0C, assuming that air is 78% N2, 21% O2, and 1% Ar.

Find the density of the atmosphere on Venus, assuming that the atmosphere is 96% CO2 and 4% N2, with a temperature of 737 K and a pressure of 92.0 atm.


Per mole, the atmosphere of a planet consists of 23% nitrogen, 76% oxygen, and 1% hydrogen. In modeling the planet’s atmosphere, use a value of 28.0 g/mol for the molar mass of N2, 32.0 g/mol for the molar mass of O2, and 2.02 g/mol for the molar mass of H2.

What is the mass of the nitrogen in 1.0 mol of this planet’s atmosphere?

The atmosphere of this planet is mixed with pentane ()CH in a ratio of 171: by mass. Find the partial pressure of pentane in this mixture at an overall pressure of 2.50 atm. Use a value of 72.2 g/mol for the molar mass of pentane.


What are the temperature and pressure of water at the triple point?

  • A273 K and 1,000 kPa
  • B373 K and 101 kPa
  • C173 K and 611 kPa
  • D273 K and 0.611 kPa
  • E0 K and 0.611 kPa


In a system, a water vapor mixture is at equilibrium at a temperature of 473 K. What is the pressure of the system?


A rigid vessel contains water vapor mixture in equilibrium at a pressure of 4.76 MPa. What is the temperature of the system?


A system contains water at a pressure of 4 MPa and a temperature of 200C. What is the phase of this water?

  • ASolid-liquid mixture
  • BSolid
  • CLiquid-vapor mixture
  • DVapor
  • ELiquid


A system contains water at a pressure of 4 MPa and a temperature of 300C. What is the phase of this water?

  • ALiquid-vapor mixture
  • BSolid
  • CSolid-liquid mixture
  • DVapor
  • ELiquid


A rigid vessel with a volume of 200 m3 contains a saturated liquid-vapor mixture with a vapor quality of 75.0%. The temperature of the vessel is maintained at 393 K. What is the total mass of the liquid-vapor mixture inside the vessel?

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