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sxWKXP-mHsA-034|It appears in your body and you might say, well if these molecules are so similar, how does your body know that it needs only L?
sxWKXP-mHsA-035|In fact, it's completely true if you were to feed a person all of D amino acids it would be protein.
sxWKXP-mHsA-036|You could eat it, but you would actually die because your body can't process the other handedness.
sxWKXP-mHsA-037|And here's a little simple example why.
sxWKXP-mHsA-038|If your hand is right and you go to shake a hand, you can detect whether you're shaking a right hand.
sxWKXP-mHsA-039|A right hand fits into your right hand.
sxWKXP-mHsA-040|Your hand is chiral and it can detect I need that same chirality to shake hands.
sxWKXP-mHsA-041|If a left hand comes in, they don't fit together right.
sxWKXP-mHsA-042|So there's a handedness that predominates, and it can be detected in nature.
sxWKXP-mHsA-044|So this achiral system doesn't have that property of I need to have one isomer to have that particular fit.
sxWKXP-mHsA-045|Chirality, a very subtle form of isomorphism, is important in nature right down to the very molecules that make up our bodies.
2wza6DXebFQ-001|Now, the pressure comes from the particles impacting the wall of the flask.
2wza6DXebFQ-002|And when they impact the wall of the flask, they impart a momentum.
2wza6DXebFQ-003|A change in momentum is a force.
2wza6DXebFQ-004|And we want the force per unit area.
2wza6DXebFQ-005|So there's a momentum and then there's how frequently the particles hit the wall.
2wza6DXebFQ-010|Their speeds, v. If there's more speed, everything else being equal, the particles are going to hit the wall more often.
2wza6DXebFQ-011|But it will be inversely proportional to the volume.
2wza6DXebFQ-012|Because everything else being equal, a larger volume, you'll have fewer collisions with the wall.
2wza6DXebFQ-013|So this frequency of collisions term depends on those three factors.
2wza6DXebFQ-014|The product of these two is going to give us a measure of the pressure.
2wza6DXebFQ-019|Now, that factor of three comes from the fact that this frequency here we kind of over account because not all the particles are heading towards the wall.
2wza6DXebFQ-020|Some are moving parallel to the wall, some are moving away from the wall.
2wza6DXebFQ-021|So we over count it a little bit, so that compensates for this.
2wza6DXebFQ-022|So we have a pressure in terms of the number of particles, their masses, their velocity squared, and the volume.
2wza6DXebFQ-025|So this expression for the pressure, the average mean square speed, the number of particles, their masses, and the volume.
rvPHWWNYC0I-009|We're talking about the structural isomers of pentane.
rvPHWWNYC0I-010|Now, there's no neat way to go from the chemical formula, C5H12, to the number of isomers.
rvPHWWNYC0I-011|You pretty much have to scratch them out on paper and rearrange the atoms and then count up the unique combinations.
rvPHWWNYC0I-012|What I've done here is I started with a straight carbon chain, the 5 carbons, I haven't drawn the hydrogens in.
rvPHWWNYC0I-013|And you'll find that you don't really need to draw the hydrogens in these straight chain hydrocarbons to come up with the isomers.
rvPHWWNYC0I-017|Now, if this branch is here or here, that's actually the same molecule.
rvPHWWNYC0I-018|So what you have-- if I move this carbon over here but I flip the whole molecule over, it's the same molecule.
rvPHWWNYC0I-019|So those are not two unique isomers.
Z08pNaGQPv8-000|When more than one electron is around an atom, those electrons have a set of four quantum numbers.
Z08pNaGQPv8-001|And they'll occupy the available orbitals around an atom, but they'll do it in very specific ways, they'll follow very specific rules.
Z08pNaGQPv8-002|One of those rules is of the four quantum numbers, n, l, m sub l, and m sub s, each electron must have a unique set.
Z08pNaGQPv8-003|No two electrons can have exactly the same quantum numbers.
Z08pNaGQPv8-004|That's called the Pauli exclusion principle.
Z08pNaGQPv8-005|Now, there's other rules that they follow.
Z08pNaGQPv8-006|For instance, if there's degenerate energy levels-- and we know when we have the p orbitals, there's three that are of the same energy.
Z08pNaGQPv8-007|How do the electrons choose to occupy those?
Z08pNaGQPv8-008|Well, there's several possibilities.
Z08pNaGQPv8-009|They could go into the same orbital, spin-up and spin-down.
Z08pNaGQPv8-010|That would give them different quantum numbers.
Z08pNaGQPv8-011|m sub s would be different, although n, l, and m sub l would be the same.
Z08pNaGQPv8-012|They could have different m sub l values and different m sub s values.
Z08pNaGQPv8-018|And indeed, if you have electrons anti-parallel, that's a little bit higher energy.
Z08pNaGQPv8-019|They like to be parallel.
Z08pNaGQPv8-020|So it turns out that the electrons like to spread out in space.
Z08pNaGQPv8-021|That makes sense, because they have negative charges.
Z08pNaGQPv8-022|You wouldn't want to cram them both in the same orbital if you didn't have to.
Z08pNaGQPv8-026|They're not disallowed by any quantum mechanical rules, but they're higher in energy.
Z08pNaGQPv8-027|So this is called Hund's rule.
Z08pNaGQPv8-028|And it turns out electrons enter degenerate orbitals the same way people get on a bus.
Z08pNaGQPv8-029|You know, if you get on a bus, there's a lot of seats and they each hold two people.
Z08pNaGQPv8-030|But if there's someone sitting in one seat, do you go in and sit right next to them in the same seat?
Z08pNaGQPv8-031|[LAUGHS] No.
Z08pNaGQPv8-032|You go sit in a seat far away from them.
Z08pNaGQPv8-033|Do you go and sit in a seat near them and face them?
Z08pNaGQPv8-035|You go and sit in the same direction facing away on the bus.
Z08pNaGQPv8-036|Electrons enter orbitals the same way people enter seats on a bus.
Z08pNaGQPv8-037|Let's look at that.
Z08pNaGQPv8-038|I've chosen to use as my model for electrons the universal eating implement, the spork.
Z08pNaGQPv8-039|I do that because sporks have a preferred orientation.
Z08pNaGQPv8-040|I can tell this spork is pointing up, and this spork is pointing down.
Z08pNaGQPv8-041|So let's bring in some sporks as electrons to these two energy levels.
Z08pNaGQPv8-043|If there's no other spins there, then it doesn't matter.
Z08pNaGQPv8-045|But the way the first one goes in determines how the second one goes in.
Z08pNaGQPv8-048|The next spin that comes in now is forced to sit next to somebody, because these are the only degenerate energy levels.
Z08pNaGQPv8-049|There may be higher energy levels up here, but these are lower energy.
Z08pNaGQPv8-051|So the next electron will go in anti-parallel.
Z08pNaGQPv8-054|Electrons are fermions.
Z08pNaGQPv8-055|They're spin 1/2, and fermions follow this Pauli exclusion principle, where no two can have exactly the same quantum numbers.
Z08pNaGQPv8-056|They can't occupy the same space at the same time.
Z08pNaGQPv8-057|You can think of that m sub s quantum number as a time quantum number.
Z08pNaGQPv8-058|It says, I'll occupy the same space, the same orbital, but I'll do it at different times.
Z08pNaGQPv8-059|M sub s is different, so we can both sit there, we just won't see each other in time.
Z08pNaGQPv8-060|It's interesting, there's another class of particles called bosons, that can have the same quantum numbers.
Z08pNaGQPv8-061|They can all collapse into exactly the same quantum state.
Z08pNaGQPv8-062|And when that happens-- and this has been proven, a Nobel Prize was awarded for this-- where a Bose-Einstein condensate occurs.
Z08pNaGQPv8-063|All the quantum particles collapse into exactly the same quantum state.
Z08pNaGQPv8-064|They exist in the same space at the same time.
Z08pNaGQPv8-065|Matter collapsed upon itself.
Z08pNaGQPv8-066|And you can Google this on the web and see some beautiful animations of a Bose-Einstein condensate.
Z08pNaGQPv8-067|Particles existing in the same space at the same time.
Z08pNaGQPv8-068|It's a quantum feature of particles.
Z08pNaGQPv8-069|They're wavelike, they can exist in the same space in the same time, if they're bosons.
Z08pNaGQPv8-070|They have an integer spin.
Z08pNaGQPv8-073|So this set of energy levels is full, I can occupy no more.
jv9_JbddC7Y-000|Equilibria are dynamic.
jv9_JbddC7Y-002|That dynamic nature allows the equilibrium to respond to a stress, to shift towards reactants or shift towards products.
jv9_JbddC7Y-003|In the case of this dissolution, let's say we had an extra source of sulfate ions.
jv9_JbddC7Y-004|So we're trying to dissolve barium sulfate, but there is some sulfate ions already in solution.
jv9_JbddC7Y-005|A common ion already exists in solution.
jv9_JbddC7Y-006|Le Chatelier's principle would predict that would make the salt less soluble.
jv9_JbddC7Y-007|Let's see if we can calculate that.
jv9_JbddC7Y-008|Let's say we dissolve barium sulfate in 0.1 molar of a sulfate solution.
jv9_JbddC7Y-012|The barium concentration times the sulfate concentration has to equal Ksp.
jv9_JbddC7Y-016|So you can essentially neglect it.