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Combined Gas Law Avogadro’s Law

Combined Gas Law Avogadro’s Law. Write out the notes that are not in italics!. The Combined Gas Law. The gas laws may be combined into a single law, called the combined gas law , that relates two sets of conditions of pressure, volume, and temperature by the following equation.

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Combined Gas Law Avogadro’s Law

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  1. Combined Gas LawAvogadro’s Law Write out the notes that are not in italics!

  2. The Combined Gas Law • The gas laws may be combined into a single law, called the combined gas law, that relates two sets of conditions of pressure, volume, and temperature by the following equation. • With this equation, you can find the value of any one of the variables if you know the other five.

  3. Applying the Combined Gas Law • A sample of nitrogen monoxide has a volume of 72.6 mL at a temperature of 16°C and a pressure of 104.1 kPa. • What volume will the sample occupy at 24°C and 99.3 kPa? • Start by converting the temperatures to kelvins.

  4. Applying the Combined Gas Law • Next, solve the combined gas law equation for the quantity to be determined, the new volume, V2.

  5. Applying the Combined Gas Law • Substitute the known quantities and compute V2. (104.1 kPa) (72.6mL) (297K) = (99.3 kPa) (289K) = 78.2mL

  6. STP • At times a problem may say a substance is at STP or standard temperature and pressure. • Standard temperature is 0°C • Standard pressure is 1atm • When a problem occurs at STP, you can put in the standard temp and pressure.

  7. Avogadro’s Principle • In the early nineteenth century, Avogadro proposed the idea that equal volumes of all gases at the same conditions of temperature and pressure contain the same number of particles. • An extension of Avogadro’s principle is that one mole (6.02 x 1023 particles) of any gas at standard temperature and pressure (0°C and 1.00 atm pressure, STP) occupies a volume of 22.4 L.

  8. Avogadro’s Law • Avogadro’s Law This law relates volume with the number of moles of a substance. V1 n1 V2 n2 =

  9. Practice avogadro’s law • A 3.2mol sample of Helium is at 1.0atm. What is the pressure if the sample is increased to 7.6moles? First solve the equation for P2 P1 n2 P2 = n1 (1.0atm) (7.6mol) Then plug in the numbers: P2 = (3.2mol) P2 = 2.4atm

  10. Worksheet time! 30 minutes

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  20. The following is the law’s mathematical expression, where n represents the number of moles. PV = nRT The Ideal Gas Law • The pressure, volume, temperature, and number of moles of gas can be related in a simpler, more convenient way by using the ideal gas law.

  21. Gases: Additional Concepts \ The Ideal Gas Law • The ideal gas constant,R, already contains the molar volume of a gas at STP along with the standard temperature and pressure conditions.

  22. The Ideal Gas Law • The constant R does the job of correcting conditions to STP. • You do not have to correct STP in a separate step.

  23. The Ideal Gas Law • The Value of R depends on the units in which the pressure of the gas is measured, as shown below. • These values are all equivalent. Use the one that matches the pressure units you are using.

  24. Applying the Ideal Gas Law • What pressure in atmospheres will 18.6 mol of methane exert when it is compressed in a 12.00-L tank at a temperature of 45°C? • As always, change the temperature to kelvins before doing anything else.

  25. Applying the Ideal Gas Law • Next solve the ideal gas law equation for P. • Substitute the known quantities and calculate P. (18.6mol) (0.0821Latm/molK) (318K) P = (12.00L) P = 40.5 atm

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