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ZFZ2J8gwIkE-016|That's what the bubbles are.
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ZFZ2J8gwIkE-017|They're coming out of solution and then they bubble to the surface.
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0Ps7ux68RMU-000|Let's look at a phase diagram for water and try to predict where the 373 kelvin isotherm is.
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0Ps7ux68RMU-006|We're trying to position the 373 kelvin isotherm on the phase diagram for water.
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0Ps7ux68RMU-007|Now, the 373 isotherm is a 100 degrees Celsius, so that's the normal boiling point.
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0Ps7ux68RMU-008|The normal boiling point is the transition between the liquid and the gas water.
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0Ps7ux68RMU-009|So if there are two phases present, I must be below the critical temperature.
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0Ps7ux68RMU-010|Remember the critical temperature, the definition is, above the critical temperature, I have a single phase regardless of the pressure.
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0Ps7ux68RMU-011|If I have below the critical point, this critical temperature, then I can have phase transitions.
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0Ps7ux68RMU-012|So the phase transition at 100 degrees C implies that I'm below the critical temperature.
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0Ps7ux68RMU-014|If you decrease the pressure, you go from liquid to gas, or if you increase the pressure, you go from the gas to the liquid.
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_7s29Q76st0-000|Let's look at three molecules and see if we can determine if they have a permanent dipole moment.
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_7s29Q76st0-001|Three molecules, carbon monoxide, carbon dioxide, and acetone.
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_7s29Q76st0-002|Which has no permanent dipole moment?
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_7s29Q76st0-003|It's interesting to note that no permanent dipole moment means a molecule will be transparent to microwaves.
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_7s29Q76st0-004|It turns out the permanent dipole moment is what allows molecules to absorb microwaves.
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_7s29Q76st0-005|It's what allows microwave spectroscopy to work, and even your microwave oven.
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_7s29Q76st0-006|So while you're thinking about which of these has no permanent dipole moment, you can think about which of these would be transparent to microwaves at the same time.
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_7s29Q76st0-013|We're looking at three molecules and trying to determine their electric dipole moments.
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_7s29Q76st0-016|Carbon monoxide.
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_7s29Q76st0-017|There's a diatomic molecule, two atoms, unequal electronegativities between oxygen and carbon.
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_7s29Q76st0-018|So there'll be an electric dipole moment in carbon monoxide.
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_7s29Q76st0-019|Carbon dioxide.
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_7s29Q76st0-020|Now here we have two bonds to consider.
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_7s29Q76st0-021|Remember, we need to consider each bond in the molecule.
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_7s29Q76st0-022|Each bond will be polar.
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_7s29Q76st0-023|Each will have a tiny dipole moment that will add to give the total dipole moment for the molecule.
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_7s29Q76st0-024|In the case of carbon dioxide, the dipole moments are equal and opposite, so they'll identically cancel out.
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_7s29Q76st0-025|How about acetone?
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_7s29Q76st0-027|Now those are not equal and opposite.
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_7s29Q76st0-028|In fact, they'll point in different directions and have different magnitudes, and they will not cancel out.
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_7s29Q76st0-030|So the answer here, carbon dioxide has no permanent dipole moment.
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_7s29Q76st0-031|Now those of you that are looking at this very closely might say, wait a minute, isn't oxygen more electronegative than carbon?
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_7s29Q76st0-032|Shouldn't this electric dipole moment point the other way?
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_7s29Q76st0-033|Shouldn't there be a higher probability of finding electrons around the more electronegative element, oxygen, in this diatomic molecule?
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_7s29Q76st0-034|Well, your initial impression would be correct.
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_7s29Q76st0-035|Your feeling from electronegativities is that this dipole moment should point in the other direction.
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_7s29Q76st0-036|And in fact, it does point from the oxygen to the carbon.
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zdupTfmI3ME-000|Let's look at the catalyzed reaction of hydrogen and oxygen to form water.
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zdupTfmI3ME-013|Now, we weren't given the reagents hydrogen and oxygen in that ratio.
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zdupTfmI3ME-014|In fact, you hardly ever are.
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zdupTfmI3ME-015|You don't provide things in exact chemical ratio and when you don't one thing will run out before the other thing.
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zdupTfmI3ME-016|One thing will be in excess.
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zdupTfmI3ME-017|And in this case, I think you can see we have much more oxygen than we need to react with one mole of hydrogen.
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zdupTfmI3ME-018|To react with one mole of hydrogen we'd only need half a mole of oxygen and we have two.
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zdupTfmI3ME-022|Hydrogen and water will produce in one to one ratios.
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zdupTfmI3ME-023|They have the same stoichiometric coefficient.
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zdupTfmI3ME-024|So one mole of hydrogen, if there's enough oxygen, which there is, will produce one mole of water.
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zdupTfmI3ME-025|But there's oxygen left over.
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zdupTfmI3ME-026|We call hydrogen here the limiting reagent because when it ran out it limited how much product I could form.
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WH4YuPwH9l8-003|So which of these transitions in thymol blue has the greatest absorbance at pH 10?
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WH4YuPwH9l8-011|We're looking at the indicator thymol blue, which is a polyprotic acid, and it has several color variations.
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WH4YuPwH9l8-015|So we're talking about thymol blue in the region where we have a pH of 10.
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WH4YuPwH9l8-016|So at pH 10, the blue form predominates.
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WH4YuPwH9l8-017|Now, if a solution appears blue, where does it absorb?
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WH4YuPwH9l8-018|Remember, solutions that appear blue absorb other regions.
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WH4YuPwH9l8-019|And something that absorbs strongly in the red will pass blue colors and appear blue.
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5_H82ywrQIY-000|Let's look at dissolving barium sulfate, a sparingly soluble solid, in water.
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5_H82ywrQIY-001|If we try to dissolve it and a little, tiny speck remains, say about a milligram remains in the bottom, what's the best way to dissolve that additional milligram?
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5_H82ywrQIY-009|We're looking at barium sulfate in water, and dissolving a tiny, milligram speck, and the most efficient way to do that.
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5_H82ywrQIY-010|Should we add some acid?
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5_H82ywrQIY-011|H2SO4?
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5_H82ywrQIY-012|Should we add barium chloride, BaCl2, or water?
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5_H82ywrQIY-013|Well, if you look at the reaction for barium sulfate solid dissolving in water, barium sulfate forms barium ions and sulfate ions.
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5_H82ywrQIY-018|What you want is more ions to get this to dissolve.
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5_H82ywrQIY-019|Sulfuric acid, H2SO4, the same thing, you're going to add more sulfate ions to solution.
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5_H82ywrQIY-021|So in this case, the best strategy is simply add more water, increase the concentration.
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5_H82ywrQIY-022|That gives you diluting these concentrations, making them smaller.
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5_H82ywrQIY-023|By Le Chatelier's principle, I'll shift to make these concentrations higher again.
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5_H82ywrQIY-024|So in this case, add more water to dissolve a one milligram speck of barium sulfate.
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aNEDU6EL8jc-000|Let's look at the course of chemical reactions.
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aNEDU6EL8jc-006|And I can calculate this value Q at any time.
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aNEDU6EL8jc-013|So I can calculate this number Q at any time.
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aNEDU6EL8jc-016|You can see they flatline here.
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aNEDU6EL8jc-017|There is no change with time for the concentrations.
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aNEDU6EL8jc-018|So if you wait long enough, these values of concentration stop changing and that means Q stops changing.
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aNEDU6EL8jc-019|It becomes a constant after some time.
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aNEDU6EL8jc-021|And your reaction quotient stops changing.
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aNEDU6EL8jc-022|It becomes a constant.
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aNEDU6EL8jc-024|That is, A and B are still changing into C and D. It's just at the same time, C and D are changing back into A and B.
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aNEDU6EL8jc-025|So macroscopically, things don't change, but the reverse and forward rates have equalized.
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aNEDU6EL8jc-026|So it's a dynamic equilibrium.
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aNEDU6EL8jc-029|So it's indeed a constant, and it's a characteristic of the chemical reaction.
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aNEDU6EL8jc-030|So if you measure lots of these K's you can predict where the reaction's going to go.
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aNEDU6EL8jc-032|The numerator is the products.
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aNEDU6EL8jc-033|So if these products are too small-- because Q is too small-- I should go make more of them.
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aNEDU6EL8jc-034|So I should go towards products.
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aNEDU6EL8jc-035|So comparing Q that you measure at any time with your known constant gives you predictive power.
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aNEDU6EL8jc-036|Which way is that reaction going to go?
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aNEDU6EL8jc-037|Same thing, if you measure Q and its bigger than K, well, that says, this numerator's too large.
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aNEDU6EL8jc-038|Too many products, I should go back to reactants, because I know Q's always go back to the K.
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aNEDU6EL8jc-039|If I wait long enough, reactions will proceed.
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aNEDU6EL8jc-040|So Q, the instantaneous concentrations, stops changing at this value of K.
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aNEDU6EL8jc-041|And it will progress towards K in a relatively straightforward monotonic fashion.
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aNEDU6EL8jc-042|So here we have Q equal K at equilibrium.
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aNEDU6EL8jc-043|Now, the approach from Q to K can be monotonic, as I've written it, but it actually could also oscillate.
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aNEDU6EL8jc-044|Whatever it is, it'll get to K eventually.
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aNEDU6EL8jc-045|So Q equals K at equilibrium.
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aNEDU6EL8jc-046|And what I have is a comparison between Q and K will tell me which direction I have to go to get equilibrium.
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aNEDU6EL8jc-047|I can measure this value of K. What I need to do is measure it at different temperatures because K will change with temperature.
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