chapter 18
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Chapter 18. The Combined Gas Law & Graham’s Law. Combined Gas Law. 10.0 cm 3 volume of a gas is collected at 75.6 kPa and 60.0 C. What would its volume be at STP? 6.12 cm 3. Combined Gas Law Problem. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 18
The Combined Gas Law
&
Graham’s Law
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Combined Gas Law
• 10.0 cm3 volume of a gas is collected at 75.6 kPa and 60.0C. What would its volume be at STP?
6.12 cm3
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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?
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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?
x 3.20 atm x 90.0 mL 0.800 atm 180.0 mL
604 K - 273 = 331 °C
302 K = 604 K
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Weather Balloons
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Weather Balloons• A weather balloon is an instrument which measures
temperature, humidity, and atmospheric pressure. The weather balloon is generally a balloon mounted with weather measuring equipment and a radio transmitter. Some weather balloons are equipped with GPS or global positioning systems for the weather station to track it more accurately.
• In North America prior to release the balloon is usually filled with hydrogen gas due to lower cost, though helium can be used as a substitute. Weather balloons may reach altitudes of 40 km (25 miles) or more where the diminishing pressure eventually causes the balloon to expand to such a degree that it pops.
• Weather balloons are sometimes cited as the cause for unidentified flying object sightings.
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A weather balloon with a volume of 305L at STP is released and rises until it expands and explodes at a pressure of
7.00 torr and a temperature of –21°C. What was the volume of the balloon when it burst?
≈ 30,600 L
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A weather balloon with a volume of 305L at STP is released and rises until it expands and
explodes at a pressure of 7.00 torr and a temperature of –21°C. How many times larger
is the balloon than when it was released?
About 100 times larger
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Diffusion
• The spreading of a gas from an area of higher concentration to an area of lower concentration.
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Which gas would diffuse throughout a room faster?
NH3(g) or HCl(g)
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Gas Diffusion and Effusion
• Graham's Law:
• Allows for the calculation of the rate of diffusion of gas molecules.
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Gas Diffusion and Effusion
Graham's Law: governs the rate of diffusion of gas molecules.
A of massmolar B of massmolar
B of RateA of Rate
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Calculate the rate of diffusion of NH3(g) compared to HCl(g)
A of massmolar B of massmolar
B of RateA of Rate
NH3 diffuses 1.47 times faster than HCl
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Use measurement to confirm the rate of diffusion of NH3(g) compared to HCl(g)
HCl NH3
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Calculate the rate of diffusion of helium compared to argon.
A of massmolar B of massmolar
B of RateA of Rate
Helium diffuses 3.2 times faster than argon
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Calculate the rate of diffusion of hydrogen compared to neon.
A of massmolar B of massmolar
B of RateA of Rate
hydrogen diffuses 3.2 times faster than neon
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Homework
• Worksheet: Combined Gas Law & Graham’s Law
• Summarize the (I) Purpose and (II) Procedure of the “Gas Laws” Lab.