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.

Q1:

On a warm day when the air temperature is 3 0 . 0 0 C , a metal can is slowly cooled by adding bits of ice to liquid water in it. Condensation first appears when the can reaches 1 5 . 0 0 C . What is the relative humidity of the air?

Q2:

Air is 2 1 % 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?

Q3:

Find the density of air at a pressure of 1.00 atm and a temperature of 20.0℃, assuming that air is 7 8 % N2, 2 1 % O2, and 1 % Ar.

Find the density of the atmosphere on Venus, assuming that the atmosphere is 9 6 % CO2 and 4 % N2, with a temperature of 737 K and a pressure of 92.0 atm.

Q4:

Per mole, the atmosphere of a planet consists of 2 3 % nitrogen, 7 6 % 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 ( ) C H 5 1 2 in a ratio of 1 7 1 : 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.

Q5:

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

  • A 0 K and 0.611 kPa
  • B 373 K and 101 kPa
  • C 273 K and 1 0 0 0 kPa
  • D 273 K and 0.611 kPa
  • E 173 K and 611 kPa

Q6:

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

  • A 4.76 MPa
  • B 3.25 MPa
  • C 0.176 MPa
  • D 1.52 MPa
  • E 0.781 MPa

Q7:

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

  • A 202℃
  • B 150℃
  • C 373℃
  • D 473℃
  • E 250℃

Q8:

A system contains water at a pressure of 4 MPa and a temperature of 2 0 0 C . What is the phase of this water?

  • ALiquid-vapor mixture
  • BVapor
  • CSolid
  • DLiquid
  • ESolid-liquid mixture

Q9:

A system contains water at a pressure of 4 MPa and a temperature of 3 0 0 C . What is the phase of this water?

  • ALiquid
  • BLiquid-vapor mixture
  • CSolid
  • DVapor
  • ESolid-liquid mixture

Q10:

A rigid vessel with a volume of 200 m3 contains a saturated liquid-vapour mixture with a vapour quality of 7 5 . 0 % . The temperature of the vessel is maintained at 393 K. What is the total mass of the liquid-vapour mixture inside the vessel?

  • A 179 kg
  • B 219 kg
  • C 359 kg
  • D 299 kg
  • E 199 kg

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