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Using Pressure and Temperature for Gas Law Calculations

Pressure Units
Unit Definition Standard Pressure*
mm Hg  (millimeters of mercury) When pressure is expressed using these units, this pressure indicates how high a column of mercury could be supported in terms of mm. 760 mm Hg
in Hg (inches of mercury) When pressure is expressed using these units, this pressure indicates how high a column of mercury could be supported in terms of inches. 29.92 in Hg
pascals (Pa) 1 pascal is the force of 1 N/m2 101325 Pa or 101.3kPa
atmospheres 1 atmosphere is standard pressure.  It is the pressure exerted on the average by the atmosphere at sea level. 1 atm
pounds per inch squared (psi) 1 psi is the force of 1 pound per inch squared  14.7psi

*Standard Pressure is defined to be the average atmospheric pressure at sea level.  

 

Temperature Units
In all gas law calculations it is necessary for the units of temperature to be expressed using an absolute temperature scale. The absolute temperature scale that we will be using will be the Kelvin scale.  Standard temperature is defined to be 273 K.
Kelvin = º C + 273
Sample Conversions
Temperature  C Temperature K
0  C 273 K (this is Standard Temperature)
100 C 373 K
-196 C (temperature of liquid nitrogen evaporating) 77 K
-273 (This temperature is called absolute zero.  At this temperature it is believed that all molecular motion stops.  This is the lowest temperature possible.) 0 K
 
D.C. Everest Senior High
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Bill Heeren, Teacher
November 16, 2013

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