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Not so long ago, in a chemistry lab far far away…. May the FORCE/area be with you. Episode I ATTACK OF THE GAS Gas, being of upmost importance to the entire galaxy and your life, is in constant battle due to the ruthless variations of temperature, pressure, and the amount of particles.
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Not so long ago, in a chemistry lab far far away… May the FORCE/area be with you Episode I ATTACK OF THE GAS Gas, being of upmost importance to the entire galaxy and your life, is in constant battle due to the ruthless variations of temperature, pressure, and the amount of particles. It is imperative that you understand properties of gases and how those ruthless variations affect the gases. You will need to make some minor assumptions to conquer this topic. However, there is certainty that you will prevail…
Gas Laws: Gay-Lussac’s and CombinedAt the conclusion of our time together, you should be able to: Describe Gay-Lussac’s Law with a formula Use Gay-Lussac’s Law to determine either a temperature or volume Combine all three laws into the Combined Gas Law Use the Combined Gas Law to determine either temperature, volume or pressure
Gay-Lussac’s Law If n and V are constant, then P α T P and T are directly proportional. • If one temperature goes up, the pressure goes up! Joseph Louis Gay-Lussac (1778-1850)
Gay Lussac’sLaw Summary The pressure and temperature of a gas are directly related, provided that the volume remains constant.
Example P1 P2 T1 T2 3.00 atm V2 298 K 325 K 3.27 L
Gay-Lussac’s Law Practice #1 P1 P2 T1 T2 1.8 atm 1.9 atm 273 K T2 288 K or 15.2 oC
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Combined Gas Law • The good news is that you don’t have to remember all three gas laws! Since they are all related to each other, we can combine them into a single equation. BE SURE YOU KNOW THIS EQUATION! No, it’s not related to R2D2
The Combined Gas Law The combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas. Boyle’s law, Gay-Lussac’s law, and Charles’ law are all derived from this by holding a variable constant.
Combined Gas Law If you should only need one of the other gas laws, you can cover up the item that is constant and you will get that gas law! = P1 V1 P2 Boyle’s Law Charles’ Law Gay-Lussac’s Law V2 T1 T2
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Combined Gas Law Problem A sample of helium gas has a volume of 0.180 L, a pressure of 0.800 atm and a temperature of 29°C. What is the new temperature(°C) of the gas at a volume of 90.0 mL and a pressure of 3.20 atm? Set up Data Table P1 = 0.800 atm V1 = 180 mL T1 = 302 K P2 = 3.20 atm V2= 90 mL T2 = ??
Calculation • P1 = 0.800 atm V1= 180 mLT1 = 302 K • P2 = 3.20 atm V2= 90 mL T2 = ?? P1 V1 P2 V2 = P1 V1T2= P2 V2 T1 T1 T2 T2= 3.20 atm x 90.0 mL x 302 K 0.800 atm x 180.0 mL T2 = 604 K - 273 = 331 °C = 604 K
Learning Check A gas has a volume of 675 mL at 35°C and 0.850 atm pressure. What is the temperature in °C when the gas has a volume of 0.315 L and a pressure of 802 mm Hg?
One More Practice Problem A balloon has a volume of 785 mL on a fall day when the temperature is 21°C. In the winter, the gas cools to 0°C. What is the new volume of the balloon?
Try This One A sample of neon gas used in a neon sign has a volume of 15 L at STP. What is the volume (L) of the neon gas at 2.0 atm and –25°C?
15 Helpful Hints On The Lab Report from Mr. T’s Vast Lab Experience!!! Hint #5. A record of data is essential. It fools the instructor into thinking that you were working.
Gas Laws: Gay-Lussac’s and CombinedLet’s see if you can: Describe Gay-Lussac’s Law with a formula. Use Gay-Lussac’s Law to determine either a temperature or volume Combine all three laws into the Combined Gas Law Use the Combined Gas Law to determine either temperature, volume or pressure
What will the new pressure (in atm) be if oxygen gas at room temperature (25.0 oC) and 1.00 atm is heated to 50.0 oC in a fixed container? • 2.00 atm • 0.500 atm • 1.08 atm • 0.923 atm • Not listed
A sample of neon gas occupies 266 mL at 25.5oC. At what temperature would the volume of this sample of gas be reduced to half its initial size? (1 atm = 101.325 kPa) • -124oC • 149oC • 119oC • -154oC • Not listed
What is the volume of CO2 at STP if the original sample of CO2 had a volume of 65.0 mL at 95.0 mm Hg and 50.0oC? • .00687 mL • 44.4 mL • 6.87 mL • 5220 mL • Not listed