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workplace. Finally, the environmental professional must understand how particulates, gases, and
vapors are generated, how they enter the human body, how they impact worker's health, and how to
evaluate particulate-, gas-, and vapor-laden workplaces.
Because air sampling is integral to just about everything the environmental professional does
and is about, in the following we include basic air sampling calculations that go hand-in-hand with
the conduction of air sampling protocols.
15.5.7.1 Air Sampling Calculations
• 1 mole = 22.4 L at STP.
• 1 mole = 24.45 L at NTP.
• Standard pressure is 760 Torr (760 mmHg at sea or atmosphere level).
• Standard temperature is 0°C or 273 K.
15.5.7.1.1 Boyle's Law Problems
Problem:
If 500 mL of oxygen is collected at a pressure of 780 mmHg, what volume will the gas
occupy if the pressure is changed to 740 mmHg?
Solution:
New volume (
V
2
) = 500 mL × (780 mmHg/740 mmHg) = 527 mL
Problem:
What is the volume of a gas at a pressure of 90 cmHg if 300 mL of the gas was collected
at a pressure of 86 cmHg?
Solution:
New volume (
V
2
) = 300 mL × (86 cmHg/90 cmHg) = 287 mL
Problem:
Calculate the pressure of a gas that occupies a volume of 110 mL if it occupies a volume
of 300 mL at a pressure of 80 cmHg.
Solution:
New pressure (
P
2
) = 80 cmHg × 300 mL/110 mL = 218 cmHg
15.5.7.1.2 Charles' Law Problems
Problem:
What volume will an amount of gas occupy at 25°C if the gas occupies a volume of 500
mL at a temperature of 0°C? Assume that the pressure remains constant.
Solution:
K = 273° + °C
New volume (
V
2
) = 500 mL × (298 K/273 K) = 546 mL
Problem:
What is the volume of a gas at -25°C if the gas occupied 48 mL at a temperature of 0°C?
Solution:
New volume (
V
2
) = 48 mL × (248 K/273 K) = 43.6 mL
Problem:
If a gas occupies a volume of 800 mL at 15°C, at what temperature will it occupy a volume
of 1000 mL if the pressure remains constant?
Solution:
New absolute pressure (
T
2
) = 288 K × (1000 mL/800 mL) = 360 K
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