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# 13.4 Up Up And Away (Calculations Practice)

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

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