Combined Gas Law The combined gas law combines Boyle’s Law and Charles’ Law

Combined Gas LawCombined Gas Law

The combined gas law The combined gas law combines Boyle’s Law and combines Boyle’s Law and

Charles’ LawCharles’ Law


Boyle’s Law PBoyle’s Law P11VV11 = P = P22VV22

Charles’ LawCharles’ Law

VV11 = =

VV22

TT1 1 T T22


PP11VV11 == PP22VV22

TT1 1 T T22

Units of PressureUnits of Pressure

Atmospheres =1 atm is the average atmospheric pressure at sea level

Torr = equal to 1/760 of an atmosphere millimeters of mercury = 1 mm Hg is the same as 1 Torr, or 1/760 atm

Kilopascals = there are 101.325 kPa in 1 atm

Standard temperature and pressure (stp)= A set of conditions defined as 273 K and 1 atm

Converting to KelvinConverting to Kelvin

Kelvin is abbreviated as K. To convert, just add 273 to whatever the Celsius temperature is.

Example: 30° Celsius = 30 + 273 = 303 K


For example: If I initially have a For example: If I initially have a gas at a pressure of 12 atm, a gas at a pressure of 12 atm, a volume of 23 L and a volume of 23 L and a temperature of 200 K, then I temperature of 200 K, then I raise the pressure to 14 atm and raise the pressure to 14 atm and increase the temperature to 300 increase the temperature to 300 K, what is the new volume of the K, what is the new volume of the gas?gas?


Begin by converting to Kelvin. It Begin by converting to Kelvin. It is not necessary in this problem. is not necessary in this problem.


Next, write down the information you Next, write down the information you know and want to know.know and want to know.

PP11 = = VV11 = = TT11 = = PP22 = = VV22 = = TT22 = =

Combined Gas LawsCombined Gas Laws


PP11 = 12 atm = 12 atm VV11 = = TT11 = = PP22 = = VV22 = = TT22 = =



PP11 = 12 atm = 12 atm VV11 = 23 L = 23 L TT11 = = PP22 = = VV22 = = TT22 = =



PP11 = 12 atm = 12 atm VV11 = 23 L = 23 L TT11 = 200K = 200K PP22 = = VV22 = = TT22 = =



PP11 = 12 atm = 12 atm VV11 = 23 L = 23 L TT11 = 200K = 200K PP22 = 14 atm = 14 atm VV22 = = TT22 = =



PP11 = 12 atm = 12 atm VV11 = 23 L = 23 L TT11 = 200K = 200K PP22 = 14 atm = 14 atm VV22 = x = x TT22 = =



PP11 = 12 atm = 12 atm VV11 = 23 L = 23 L TT11 = 200 K = 200 K PP22 = 14 atm = 14 atm VV22 = x = x TT22 = 300 K = 300 K


Now plug in the information you have Now plug in the information you have . . .. . .

PP11VV11 == PP22VV22

TT1 1 T T22

12atm(23L)12atm(23L) ==

14 atm (x)14 atm (x)

200K200K 300K 300K


Cross multiply to solve for xCross multiply to solve for x 12atm(23 L)(300K) = 200 K (14L)(x)12atm(23 L)(300K) = 200 K (14L)(x)

82800 = 2800x82800 = 2800x

x = 29.57 Litersx = 29.57 Liters

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Combined Gas Law The combined gas law combines Boyle’s Law and Charles’ Law