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# 13.4 Up Up And Away (Calculations Practice)

## on Jan 26, 2008

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## 13.4 Up Up And Away (Calculations Practice)Presentation Transcript

• Up, Up and Away – Using the Gas Laws
• We will find out:
• How the gas laws allow calculations to be made to determine Pressure, Volume and/or Temperature of a gas at different states.
• How the particles behave in a gas
• Ideal Gas Laws
• So far, we have found out:
• PV = nRT
• for all gases, where:
• p = Pressure in Pascal or Nm -2
• V = Volume
• n = number of moles
• R = molar gas constant 8.31 J mol -1 K -1
• T = Temperature in Kelvin
•
• Manipulating Using Gas Equation
• The Ideal Gas Law equation demonstrates:
• As Temperature increases, so does Pressure
• and/or
• As Temperature increases, so does Volume
• As the amount of gas (number of moles) increases, so does Pressure and/or Volume
• For 2 different states of a sample of gas:
• P 1 V 1 /T 1 = P 2 V 2 /T 2
• Where X 1 = Value in state 1 etc.
• See question 3 of Using the ideal gas relationships 40S
• Using P 1 V 1 /T 1 = P 2 V 2 /T 2
• A sample of gas with a pressure of 100 000 Pa has a volume of 5 litres at a temperature of 7 °C. The pressure now drops to 80 000 Pa and the temperature increases by 40 °C.
• Calculate the new volume.
http://intro.chem.okstate.edu/1314F00/Laboratory/GLP.htm
• Density
• What is the density of a gas when PV = nRT?
• Clues:
• Density (  ) = Mass/Volume…
• Number of Moles (n) = Mass / Molar Mass (M)
• Density
• PV = nRT and  = Mass/Volume
• Therefore
• Volume = Mass/ 
• Mass = Molar Mass (M) x Number of Moles (n) = Mn
• Therefore
• PV = P x Mass/  = PMn/  = nRT
• Therefore
• PM/  = RT
•  = PM/RT
• Kinetic theory
• The molecules exert a force when they hit the sides of the container and the sides of the container exert a force on each molecule
But what does it depend on…?