GAS LAWS
Conceptual Examples and Concepts
Basic Problem Solving
Conceptual Examples: Avogadro's Law
• If you double the number of moles in a container while holding temperature and pressure
constant, what happens to the volume?
Conceptual Examples: Avogadro’s Law
• If you halve the number of moles in a container while holding
temperature and volume constant, what happens to the pressure?
Conceptual Examples: Boyles
• If you double the size of a container while
holding temperature and moles constant,
what happens to the pressure?
2 atm
Conceptual Examples: Charles Law
• If you halve the temperature while holding moles
and pressure constant. What happens to the
volume?
Conceptual Examples: Charles Law
• If you halve the temperature while holding moles and
volume constant. What happens to the pressure?
For each of the following situations, state whether the stated
variable would increase or decrease, and if possible by how
much. Assume anything not mentioned is held constant.
• Temperature (kelvin) doubles, volume is halved. What happens to pressure?
• Temperature (kelvin) doubles, volume is doubled. What happens to pressure?
• Volume doubles, pressure doubles. What happens to temperature?
• Volume triples, pressure is decreased to 1/3 of its original. What happens to temperature?
• Temperature is doubled and half of the gas is removed?
CONCEPTUAL PROBLEMS
(this will allow some troubleshooting when you start gas calculation problems.)
• Explain why rapid changes in altitudes cause ear pain?
• Explain why scuba divers must not hold their breath while coming to the surface?
• If a gas is collected over water is that gas pure (see picture)?
REVIEW QUESTIONS
(things you’ll need to remember for gas Problems)
• Be sure to review, stoichiometry, empirical formulas, and balancing chemical reactions
• Chapters 5 and 8.
• If you didn’t learn this the first time around you’ll start to run into problems in this section.
REVIEW QUESTIONS
• The empirical formula of a species is CH2. Its molecular mass is 84
g/mol. What is its molecular formula?
CHALLENGE QUESTION
With hindsight, Harrison Okene probably should have seen the signs. All of the ingredients were in place: He was young,
happy, and gainfully employed as a cook on a Chevron service tugboat. Also, he was about to get married in a few days.
All he had to do before his wedding was finish this one ... last ... mission.
Of course, said mission turned into the most terrifying disaster movie this side of the SS Poseidon. In the early morning of
May 26, 2013, Okene had just gotten up and was in the bathroom. Suddenly, his ship was hit by what a spokesman later
called a "sudden ocean swell" (which is presumably corporate speak for "Shit, we accidentally summoned Cthulhu again").
Okene could only watch helplessly as his daily life turned into a trip to Rapture. The tugboat capsized and plummeted 100
feet below the surface, with him still inside. Trapped in the dark abyss with no one else in sight and wearing nothing but his
boxers, Okene waded through the ship's corridors (which were slowly filling with icy water). He managed to locate a source
of light, some Coca-Cola, and a few tools, and he made it to a relatively safe corner of the ship.
Okene ended up bunking in a 4-foot air pocket under the surface, holding back the water as best he could and stacking
mattresses as the cold water rose to keep dry. To make things worse, sharks and barracudas soon started roaming the ship's
interiors in search of a meal. He could hear them fighting for the remains of his shipmates in other rooms and swimming in the
water just below him. He had no food. The salt water and the bumps from the accident were wearing his skin raw. There was
far too little air for him to breathe, and he was ruining it with every breath by puffing out carbon dioxide. He would not last
beyond a couple of hours.
Except that he totally did. In fact, he managed to stay alive for 62 hours.
Here's how…….
****Exerpt taken from Cracked.com “Survival stories almost too miraculous to be real”****
Theoretically how could he have survived?
We won’t do the math, we’ll just talk though it in concept.
Challenge question: Do the math (you’ll need the ideal gass law, PV=nRT) and see what happens. State all assumptions you
make. I’ll post my results online and link to some people who did it other ways.