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7A5UuW3EJPc-014|This reaction happens to be exothermic, and we could have predicted that because what's happening here is a bond is being formed.
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7A5UuW3EJPc-015|You're going from a monomer to a dimer, a nitrogen-nitrogen bond turns out to be what is exactly formed here.
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7A5UuW3EJPc-016|But even without knowing where the bond is, you can tell there's a bond formation, and bond formations are always exothermic.
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7A5UuW3EJPc-017|It always takes energy to break bonds, and energy is always released when I make bonds.
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7A5UuW3EJPc-018|So this is a bond making, a bond formation.
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7A5UuW3EJPc-023|Because we're about 25 degrees C here in the studio.
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7A5UuW3EJPc-025|They'll remain at equilibrium because at equilibrium, no free energy difference between the products and reactants.
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7A5UuW3EJPc-026|They interchange freely.
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7A5UuW3EJPc-027|It's a dynamic equilibrium, but it's one where k is constant.
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7A5UuW3EJPc-028|And remember, regardless of the starting conditions, I'll achieve this k.
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7A5UuW3EJPc-030|That's the nature of equilibrium, a balance between free energy and a constant value we call the equilibrium constant.
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dEFsl3YYwuM-000|In this lesson, we're going to talk about bonding.
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dEFsl3YYwuM-001|One of the kinds of bonds, ionic bonds, are formed when a positively-charged ion is attracted to a negatively-charged ion.
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dEFsl3YYwuM-002|That is, the electron is physically transferred from one atom to the other.
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dEFsl3YYwuM-003|An example is sodium chloride, where the electron leaves sodium and lands on the chlorine.
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dEFsl3YYwuM-004|Now energetically, it takes more energy to remove the electron from sodium than you get back when the electron lands on the chlorine.
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dEFsl3YYwuM-005|So it's the resulting plus-minus interaction that's very favorable, that makes the overall bond formation possible.
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dEFsl3YYwuM-008|We're going to talk about all the kinds of bonds, though, today in the spectrum of covalent to polar covalent to ionic bonds.
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hFWhPUDIhNY-000|When gasses deviate from ideal behavior, we can still calculate P, V and T using equations, and there's a variety of them.
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hFWhPUDIhNY-001|The one I've listed here is called a Van der Waals equation.
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hFWhPUDIhNY-002|A Van der Waals equation looks a lot like the ideal gas expression.
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hFWhPUDIhNY-008|Let's look at some of these A and B parameters.
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hFWhPUDIhNY-009|Here's helium.
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hFWhPUDIhNY-015|It has Van der Waals dispersion interactions, it has dipole-dipole interactions, and hydrogen bonding interactions.
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hFWhPUDIhNY-016|That leads to the largest value for A.
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hFWhPUDIhNY-017|Notice the value for b is about the same for all these.
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hFWhPUDIhNY-018|The volume of the particle on the grand scale is about the same order of magnitude for all these particles.
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hFWhPUDIhNY-020|So when the ideal gas behavior no longer applies, I can apply the Van der Waals equation, and still calculate P, V, and T.
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L348PufMnqw-000|Let's do a calculation involving a sparingly soluble salt, silver chloride, and a very soluble salt, sodium chloride.
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L348PufMnqw-001|The Ksp, the solubility product, for silver chloride is 1.6 times 10 to the minus 10.
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L348PufMnqw-002|For sodium chloride, we don't report a Ksp because it's very soluble.
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L348PufMnqw-003|Sodium and chloride ions dissociate completely in solution, and the Ksp would be very much bigger than one.
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L348PufMnqw-004|In fact, we really only report Ksp, solubility products, for salts that are sparingly soluble that have Ks less than 1.
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L348PufMnqw-005|So all sodium salts, really, and all chlorides are very soluble.
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L348PufMnqw-006|So they dissociate completely, and you can assume safely 100% dissociation in water.
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L348PufMnqw-014|So x times x equals Ksp.
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L348PufMnqw-019|Doesn't matter if I put more solid silver chloride in the flask.
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L348PufMnqw-020|The equilibrium has been reached, and the product of the silver ions and the chlorine ions always has to be 1.6 times 10 to the minus 10.
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L348PufMnqw-024|The sodium ions don't do anything.
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L348PufMnqw-025|They're not involved in this equilibrium.
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L348PufMnqw-026|And when sodium and chlorine ions are in solution, they stay as sodium chloride, the separate ions.
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L348PufMnqw-027|But when silver and chloride ions are together in solution, they tend to precipitate to form silver chloride.
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L348PufMnqw-028|So let's see that happening.
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L348PufMnqw-034|That's because this equilibrium constant is very small so this reaction doesn't go very far towards the products.
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L348PufMnqw-035|So these concentrations, x, are small, and I think they'll be very small with respect to 0.2.
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L348PufMnqw-036|So this 0.2 plus x is essentially 0.2.
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L348PufMnqw-037|It's 0.2 plus a tiny amount.
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L348PufMnqw-041|That's 10 to the 4th times less soluble than without this chloride ions in solution.
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L348PufMnqw-042|So this common ion reduces the solubility of silver chloride by a factor of 10 to the 4th.
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L348PufMnqw-043|That's the common ion effect, and this is how we do common ion effect calculations.
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49GgQNfExf8-000|Conversion factors are used commonly in chemical calculations.
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49GgQNfExf8-001|You convert one set of units to another set of units and almost, anything can be used as a conversion factor.
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49GgQNfExf8-002|So any expression of equality can be used as a conversion factor.
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49GgQNfExf8-007|Now I can take this, that has value of 1 and multiply it.
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49GgQNfExf8-008|It's the multiplicative identity 1.
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49GgQNfExf8-009|I can multiply it by anything and not change the value, but the units will change.
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49GgQNfExf8-010|So I can use conversion factors to change my units or dimensions from one unit or one dimension to another.
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49GgQNfExf8-012|And I can use this as a conversion factor.
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49GgQNfExf8-013|So let's try that.
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EmCdAb0yiBM-000|Let's do a calculation involving a hydrogen atom where we assume the hydrogen atom behaves like a particle in a box.
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EmCdAb0yiBM-001|And that's not a bad assumption.
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EmCdAb0yiBM-002|The hydrogen atom has an electron that's bound around a nucleus, that's an electron that has boundaries on it.
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EmCdAb0yiBM-003|And remember, when you take a wave like property, and that's the electron, and put boundaries on it, you naturally get quantized energy levels.
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EmCdAb0yiBM-004|So let's do a quantum mechanical calculation on a hydrogen atom.
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EmCdAb0yiBM-005|Already at this point, in Chem 1, we can do a quantum mechanical calculation.
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EmCdAb0yiBM-008|So the particle energy levels depend only on the length of the box and the mass of the particle.
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EmCdAb0yiBM-009|We know both those things, so let's do the calculation.
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EmCdAb0yiBM-010|150 picometer box, an electron mass that we know, n we know, h we know.
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EmCdAb0yiBM-011|We can simply say, well, if it's a transition, I have to subtract n3 from n equal 2.
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EmCdAb0yiBM-012|I can do that.
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EmCdAb0yiBM-014|Always use meters, kilograms, and seconds-- joules for energy.
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EmCdAb0yiBM-017|Lambda the wavelength is what we want, and we can calculate that.
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EmCdAb0yiBM-018|So if this energy is hc over lambda, then lambda is hc over the energy.
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EmCdAb0yiBM-021|So this is a very hand-wavy, approximate calculation.
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EmCdAb0yiBM-022|But you get kind of in the same ballpark, within a factor of one order of magnitude.
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EmCdAb0yiBM-023|A factor of about tenish of the wavelength, just doing a simple particle-in-the-box calculation.
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EmCdAb0yiBM-024|That's the beauty of quantum mechanics.
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EmCdAb0yiBM-025|It has a lot of power to express the very tiny properties of matter.
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vQ_ujXXGRZs-000|Let's look at a system where we take copper metal and immerse it in sulfuric acid solution.
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vQ_ujXXGRZs-008|We're talking about immersing some copper metal in sulfuric acid solution.
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vQ_ujXXGRZs-009|So we want to know what is the more stable state-- copper ions, hydrogen gas, or will no reaction occur?
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vQ_ujXXGRZs-012|So the favored state is copper metal over hydrogen gas.
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vQ_ujXXGRZs-013|And in fact, this half cell would effectively cause the hydrogen half cell to run in reverse.
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vQ_ujXXGRZs-015|So essentially, we're already at the favored state.
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vQ_ujXXGRZs-016|We're at the product state already-- copper metal and hydrogen ions.
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vQ_ujXXGRZs-017|So this reaction will not proceed any further.
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vQ_ujXXGRZs-018|The free energy difference here is negative K is greater than 1.
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vQ_ujXXGRZs-019|The products are favored.
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vQ_ujXXGRZs-020|And the products are essentially where we started here.
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5t3xzqSPgMo-000|Let's look at a chemical reaction and determine what temperature range it will be favorable for.
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5t3xzqSPgMo-001|So where is delta G negative?
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5t3xzqSPgMo-002|The chemical reaction, carbon dioxide and calcium oxide forming calcium carbonate, the formation of limestone essentially.
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5t3xzqSPgMo-004|The question I have-- what temperature range is this reaction spontaneous as written?
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5t3xzqSPgMo-013|We're looking at carbon dioxide and calcium oxide forming calcium carbonate.
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5t3xzqSPgMo-015|So kilojoules and jewels, a factor of 1,000 between the two.
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5t3xzqSPgMo-016|Now, delta S is negative.
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5t3xzqSPgMo-017|So if I'm talking about the free energy, I have a minus T delta S contribution.
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5t3xzqSPgMo-018|The minus T delta S contribution with a minus delta S will have a positive overall contribution.
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5t3xzqSPgMo-024|For temperatures less than 1,000, then the T delta S term is less than magnitude the delta H term.
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5t3xzqSPgMo-025|So this positive contribution is smaller than this negative contribution, so overall delta G is negative.
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