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Chapter 13

Chapter 13. The Gas Laws. Robert Boyle studied how gas volume varied with changes in pressure. Boyles Law - The volume of a fixed mass of gas varies inversely with the pressure at constant temperature. P 1 V 1 = P 2 V 2. Demo soda can, vacuum jar, marsh-mellow man, spud gun, ete.

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Chapter 13

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  1. Chapter 13 The Gas Laws

  2. Robert Boyle studied how gas volume varied with changes in pressure.

  3. Boyles Law - The volume of a fixed mass of gas varies inversely with the pressure at constant temperature. P1V1 = P2V2 Demo soda can, vacuum jar, marsh-mellow man, spud gun, ete

  4. How is this related to Boyles’ Law ?

  5. Jacques Charles studied the variation of gas volume with changes in temperature. • Charles found that the volume of a gas changes by 1/ 273 of the original volume for each Celsius degree, at constant pressure.

  6. Using this information he was able to predict the value of absolute zero, the point where all motion stops. -2730C

  7. Charles’s Law- The volume of a fixed mass of gas at constant pressure varies directly with the Kelvin temperature.

  8. Charles Law Math V1 = V2 or V1T2 = V2T1 T1 T2

  9. Lord Kelvin ak Sir William Thompson • Kelvin didn’t like negative numbers, so he created a system that started at the coldest possible temperature. • - 273°C became 0° K

  10. To convert celsius to kelvin, • Add 273 • To covert kelvin to celsius • Subtract 273 All temperatures in all gas law problems must be in degrees Kelvin

  11. Joseph Gay-Lussac studied the variation of gas pressure with changes in temperature.

  12. Gay-Lussac Law – The pressure of a fixed mass of gas at constant volume varies directly with the Kelvin temperature. P1 = P2 or P1T2 = P2T1 T1 T2

  13. Unknown math guy Combined the above three equations in to the Combined Gas Law • P1V1 = P2V2 or P1V1T2 = P2V2T1 • T1 T2

  14. Daltons law of Partial pressure – The total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases.

  15. Math PT = P1 + P2 + P3 + ……..

  16. Avogadro’s Law - Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. • Thus Molar Volume - The volume occupied by one mole of a gas at STP is known as the standard molar volume of a gas, it is 22.4 liters. 1 Mole of a gas = 22.4 liters @ STP.

  17. Ideal Gas law - The ideal gas law is the mathematical relationship of pressure, volume, temperature and the number of moles of a gas. ( Combined gas law and Avogadro’s law , combined )

  18. Math PV = nRT • P is pressure in ATM, V is volume in Liters, T is temperature in degrees K • And r is a gas constant, which varies according to the units of pressure used. • When P is ATM r = .0821 • mmHg r = 62.4 • Kpa r = 8.31 • For any other pressure convert the pressure to one of the three above.

  19. Molar mass and density with the Ideal gas law PV = nRT substitute n = m PV = mRT M M mass / molar mass = moles To find molar mass rearrange to M = mRT PV

  20. Density substitute m = D V M = mRT PV M = DRT P

  21. Rearrange this to solve for density D = MP RT

  22. Grams X 1 mole X moles looking for (from equation) X FW of looking forGiven FW of given moles given (from equation) 1 mole of looking for • Remember –mass/mass problems Now we can use 1 mole = 22.4 liters @STP to find moles given, or convert moles to volume at STP. If the given information about the gas is not at STP , we can use PV = nRT to do the same thing. Instead of calling them just mass / mass problems we can call them Gas / mass and mass / gas problems

  23. Also have to divide the water level difference by 13.6 to convert it to mm Hg

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