Gas Laws & Chemistry

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  • Gas Laws & Chemistry

    1. 1. Gas Laws and Chemistry• Some Background • Standard Temperature and Pressure (STP) • Molar Volume of Gas @ STP • 22.4 liters
    2. 2. What is STP?• Standard Temperature oK=
oC

+

273 • Measured in Kelvin 20oC=
293oK not Celsius• Standard Pressure • 760 mm Lord Kelvin
    3. 3. Boyle’s Law• Volume varies inversely with pressure Robert Boyle
    4. 4. An Application of Boyle’s Law• What would be the volume of 15 liters of gas if the pressure changed from 700 mm to 850 mm?15
liters

x

700
mm

=
12.35
liters
 
 
 




850
mm
    5. 5. Charles’s Law• Volume varies directly with temperature Jacques Charles
    6. 6. An Application of Charles’s Law...• What would be the volume of 20 liters of gas at 25oC if the temperature were changed to 0oC? Convert
oC
to
oK 25oC
(25oC
+
273

=

298oK)

 0oC
(0oC
+
273
=
273oK) 20
liters
x
273oK
=

18.32
liters 
 
 
 






298oK A balloon on dry ice
    7. 7. Gay-Lussac’s Law• Pressure varies directly with temperature Joseph Gay-Lussac
    8. 8. Application of Gay-Lussac’s Law• What would be the change in pressure of a fixed volume of gas at 40oC and 600 mm pressure, if the temperature were increased to 80oC ? 600
mm
x
353oK

=

676.67
mm 
 
 
 






313oK
    9. 9. Combined Gas Law Problem• What would be the volume of 75 liters of a gas at 30oC and 700 mm pressure if the temperature and pressure were changed to 70oC and 800 mm? 75
liters
x

343oK

x


700
mm
=
74.29
liters





 
 
 






303oK







800
mm








    10. 10. Dalton’s Law of Partial Pressures• The total pressure of a mixture of gases is equal to the sum of the partial pressures of the gases
    11. 11. Combining the Gas Laws to Solve a Quantitative Problem Mg + 2 HCl MgCl2 + H2 • If 0.5 grams of Mg are completely reacted with HCl to form H2, how many liters of H2 will be collected over water at 30oC and a pressure of 700 mm?0.5
g
Mg

x

1
mole
Mg

x

1
mole
H2

x

22.4
liters
H2


=
0.46
liters
H2
@
STP
 















24.31
g
Mg




1
mole
Mg







1
mole
H2
    12. 12. The Final Step... • Take volume of H at STP and convert it to 2 lab conditions using Boyle’s, Charles’s, and Dalton’s LawsDalton’s
Law
correction700
mm
(pressure
at
lab
conditions)
–
31.8
mm
(water
vapor
pressure)
=
668.2
mm0.46
liters
H2

x

760
mm

x

303oK

=

0.58
liters
of
H2
at
lab
conditions
 
 

















668.2
mm



273oK

    ×