Element of the Day At
Emilio Segrè
Astatine (as­tә­teen), from the Greek astatos "unstable", is a radioactive chemical element with the symbol At and atomic number 85. It occurs on Earth only as the result of the radioactive decay of heavier elements. All of its isotopes are short­lived; the most stable is astatine­210, with a half­life of 8.1 hours. Accordingly, much less is known about astatine than most other elements. What properties are known accord with it being a heavier analog of iodine; many other properties have been estimated, based on the same premise.
Elemental astatine has never been viewed – a sufficient­sized chunk to be viewed by the naked eye would be immediately vaporized by its radioactive heat. Chemically, astatine behaves more or less as a halogen, being expected to form ionic astatides with alkali or alkaline metals; it is known to form covalent compounds with nonmetals, including other halogens
Astatine was first produced by Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè at the University of California, Berkeley in 1940. Three years later, it was found in nature; however, with an estimated amount of less than 28 grams at any given time, this is one of the least abundant elements.
What is the name of HAt?
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Chemistry
1. Element of the Day
2. Review POGIL/Demonstration
3. Ideal Gas Law
4. ChemThink Activity
5. Begin Homework
Announcements
Due Today: Finish POGIL Activity
Due Thursday: Finish ChemThink Activity, read pages 373 to 378 and complete gases worksheet.
Cell Biology Review: Sunday May 6th or Tuesday May 8th in room 312
Evolution Review: Sunday May 13th or Tuesday May 15th in room 326
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Review/Turn in POGIL
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Notes: Gases
Boyle's Law
Brief balloon/syringe demo
PV = k
where:
P =
V =
k =
Boyle's Law: where k is a constant at a specific temperature for a given amount of gas.
Rearranging the equation above so that P and V are on opposite sides yields:
\
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Notes: Gases
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Key Terms
Absolute zero: Charles's Law: V = bT
Where:
V = b = T = Question: According to Charles's Law, what volume would a gas at 0 K occupy?
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Notes: Gases
Example Problem 1:
1. A 2.45­L sample of nitrogen gas is collected at 273 K and heated to 325 K. Calculate the volume of the nitrogen gas at 325 K. Assume constant pressure.
Example Problem 2:
A sample of oxygen gas has a volume of 4.55 L at 25 °C. Calculate the volume of the oxygen gas when the temperature is raised to 45 °C. Assume constant pressure.
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Notes: Gases
Questions
If we double the number of particles while maintaining constant temperature and pressure, what happens to the volume?
If we reduce by 2/3rds the number of particles while maintaining constant temperature and pressure, what happens to the volume?
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Notes: Gases
Avogadro developed the equation to relate number of particles to volume.
V = an
V/n = a
Where:
V= n = a = 9
Notes: Gases
Example Question 1
If 2.55 mol of Helium gas occupies a volume of 59.5 L at a particular temperature and pressure, what volume does 7.83 mol of helium occupy under the same condition?
Example Question 2
If 4.35 g of neon gas occuypies a volume of 15.0 L at a particular temperature and pressure, what volume does 2.00 g of neon gas occupy under the same conditions?
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Notes: Gases
Combined gas law!
WE already know the following relationships
1. PV = k or V =
2. V = bT
3. V = an
These relationships show that volume is dependent upon the following:
where R is the universal gas constant. When the pressure is expressed in atmospheres and the volume is in liters, R has the value 0.08206 L atm/K mol
The ideal gas law is typically written as:
Assumptions that underlie this equation:
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Notes: Gases
Combined gas law!
Example 1
A 2.50 ­ mol sample of nitrogen gas has a volume of 5.50 L at a temperature of 27 °C. Calculate the pressure of the nitrogen gas.
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Notes: Gases
Combined gas law!
Example 2
A 5.00 ­ mol sample of oxygen gas has a pressure of 1.25 atm at 22 °C. What volume does the gas occupy?
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Start ChemThink
1. One computer per student.
2. Go to www.chemthink.com
3. Enter your username and password. Students that have not entered into ChemThink use the information below to enter the web site, then change your password.
4. Complete Gases ­> Behavior of Gases both Tutorial and Question Set.
Student
Username
Password
Taylor Ahlquist
Ahlquist
123456
Matthew Alderson
Alderson
123456
Sara Turpen Turpen 123456
Annika van Houte
van Houte
123456 14
Exit Question
How are number of moles and volume of a gas related to each other?
Reminder
Due Thursday: Finish ChemThink Activity, read pages 373 to 378 and complete gases worksheet.
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