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Gas Laws Day 2 Boyle, Charles and Gay-Lussac

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The Gas Laws The gas laws apply to ideal gases, which are described by the kinetic theory in the following five statements. Gas particles do not attract or repel each other. Gas particles are much smaller than the spaces between them.

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The Gas Laws No kinetic energy is lost when gas particles collide with each other or with the walls of their container. All gases have the same kinetic energy at a given temperature. Gas particles are in constant, random motion.

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Boyles Law: Pressure and Volume Robert Boyle ( ), an English scientist, used a simple apparatus pictured to compress gases.

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Boyles Law: Pressure and Volume After performing many experiments with gases at constant temperatures, Boyle had four findings. a) If the pressure of a gas increases, its volume decreases proportionately. b) If the pressure of a gas decreases, its volume increases proportionately.

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Boyles Law: Pressure and Volume By using inverse proportions, all four findings can be included in one statement called Boyles law. c) If the volume of a gas increases, its pressure decreases proportionately. d) If the volume of a gas decreases, its pressure increases proportionately.

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Boyles Law: Pressure and Volume Boyles law states that the pressure and volume of a gas at constant temperature are inversely proportional. Click box to view movie clip. The equation for Boyles law P 1 V 1 =P 2 V 2 When Temperature and moles are unchanged.

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Applying Boyles Law A sample of compressed methane has a volume of 648 mL at a pressure of 503 kPa. To what pressure would the methane have to be compressed in order to have a volume of 216 mL? Examine the Boyles law equation. You need to find P 2, the new pressure, so solve the equation for P 2. V1V1 =P1P1 V2V2 P2P2 V2V2 V2V2

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Applying Boyles Law Substitute known values and solve. V1V1 =P1P1 P2P2 V2V2 (648mL)=(503kPa)P2P2 216mL = 1510kPa

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Charless Law When the temperature of a sample of gas is increased and the volume is free to change, the pressure of the gas does not increase. Instead, the volume of the gas increases in proportion to the increase in Kelvin temperature. This observation is Charless law, which can be stated mathematically as follows. V1V1 T1T1 = V2V2 T2T2

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Charless Law Gases: Basic Concepts Topic 13 Topic 13 Click box to view movie clip.

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Applying Charless Law A weather balloon contains 5.30 kL of helium gas when the temperature is 12°C. At what temperature will the balloons volume have increased to 6.00 kL? Start by converting the given temperature to kelvins.

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Applying Charless Law Next, solve the Charless law equation for the new temperature, T 2. V1V1 T1T1 = V2V2 T2T2 T2T2 T2T2 T1T1 T1T1 V1V1 V1V1

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Applying Charless Law Then, substitute the known values and compute the result. Finally, convert the Kelvin temperature back to Celsius. New Temperature = 323 – 273 = 50 o C T2=T2= T1T1 V2V2 V1V1 = (285K)(6.00kL) (5.30kL) =323K

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Gay Lussacs Law This law represents the relationship between pressure and temperature… you will see it is very similar to the Charles law, and calculations are similar. P1P1 T1T1 = P2P2 T2T2

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practice A gas system has an initial temperature of 135°C with the pressure unknown. When the temperature changes to °C the pressure is found to be 1.67 atm. What was the initial pressure in atm? First solve Gay-Lussacs law for P 1 then plug in the variables

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practice P1P1 T1T1 = P2P2 T2T2 T1T1 T1T1 = (1.67atm)(408K) Change temp to kelvin… T 1 = 135C +273= 408K T 2 = C = 49.9K 49.9K =13.65atm

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