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Gas Laws

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Standard Temperature and Pressure (STP)

  • STP is Standard Temperature and Pressure. In order to compare volumes of gases, it is necessary to know the temperature and pressure at which the volumes are measured. Scientists have agreed on standard conditions of 1 atm pressure and 0 °C.
  • Standard Temperature is 0°C or 273 K.
  • Standard pressure is 101.3 kPa, 1 atm, or 760 mmH

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  • One mole of a substance is equal to 6.022 × 10²³ units of that substance (such as atoms, molecules, or ions)

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List three factors that can affect the pressure of a gas.

  • Amount of gas present
  • Volume
  • Temperature

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Units of…

  • Temperature
    • Kelvin, Fahrenheit and Celsius
    • 273K = 0C = 32F
  • Pressure
    • Kilopascal (kPa)
      • Standard atmospheric pressure is 101.325 kPa
    • Atm (atmospheric pressure)
      • 1 atm = 101.325 kPa
    • mmHg (millimeters of mercury)
      • 760 mmHg = 1 atm = 101.325 kPa
    • Torr

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Pressure

The amount of force exerted on a given area of surface.

3 types of Pressure

1. Absolute Pressure

vacuum/air free space

changes w/ location

atmospheric pressure

2. Gauge Pressure

difference between absolute pressure and atmospheric pressure

relative pressure

3. Differential Pressure

used for flow and level measurement applications

helps to measure the pressure difference between two different points

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Boyle’s Law

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This Photo by Unknown Author is licensed under CC BY-SA

This Photo by Unknown Author is licensed under CC BY-SA-NC

Boyle’s Law:

The volume of a sample of gas is inversely proportional to its pressure, if the temperature remains constant.

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P1V1 = P2V2

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Charles’ Law

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Charles Law can also be written as

V1T2 = V2T1

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Gay Lussac’s Law

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Gay-Lussac's Law states that the pressure of a given mass of gas varies directly with the absolute temperature of the gas, when the volume is kept constant.

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Combined Gas Law

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The Combined Gas Law expresses the relationship between the pressure, volume, and absolute temperature of a fixed amount of gas. For a combined gas law problem, only the amount of gas is held constant

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Ideal Gas Law

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An ideal gas is one that follows the gas laws at all conditions of temperature and pressure. An ideal gas perfectly fits all assumptions of the kinetic theory of gases.

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A real gas does not always behave according to the assumptions of the kinetic theory.

Extremely high pressures and low temperatures would cause a gas not to conform to ideal gas behavior.

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  1. Gases consist of large numbers of tiny particles that are far apart relative to their size.
  2. Collisions between gas particles and between particles and container walls are elastic collisions.
  3. Gas particles are in continuous, rapid, random motion.
  4. There are no forces of attraction or repulsion between gas particles.
  5. The average kinetic energy of gas particles depends on the temperature of the gas.