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AlwmlHuZRUU-026|I can take the difference of those two.
AlwmlHuZRUU-027|And now I'll have high amplitude on this side.
AlwmlHuZRUU-028|This side will become green, this side will become red.
AlwmlHuZRUU-029|And I'll have high amplitude on this side, 180 degrees from this high amplitude.
AlwmlHuZRUU-030|This is a combination of s minus the pz.
AlwmlHuZRUU-036|I still have my remaining p orbitals that I didn't use.
AlwmlHuZRUU-037|I used the pz, so the px and the py are still available.
AlwmlHuZRUU-038|But I have a new set, two sps, and a px, and a py.
AlwmlHuZRUU-039|Those are the atomic orbitals that are appropriate for a 180 degree bond angle.
3CHic39yxjs-000|Let's look at a couple of filters and how they'll affect a blue object.
3CHic39yxjs-001|So three possible filters put in front of a blue object.
3CHic39yxjs-009|So we've got a blue object.
3CHic39yxjs-010|We're going to put filters between the blue object and us.
3CHic39yxjs-011|And we're going to see what we see.
3CHic39yxjs-012|So a blue object, wavelengths of blue light are being emitted from that object.
3CHic39yxjs-013|That's why it appears blue.
3CHic39yxjs-014|How do we make it appear black?
3CHic39yxjs-016|So we need to find a filter that absorbs strongly in the blue.
3CHic39yxjs-017|And that is filter number two.
SKDF7sz_wgI-000|Let's see if we can deduce an atomic radius from the information we have so.
SKDF7sz_wgI-001|Far we haven't really talked about the trend in atomic radius.
SKDF7sz_wgI-002|We've talked about ionization energy and electron affinity.
SKDF7sz_wgI-003|But you might be able to surmise how the atoms go based on our other atomic trends.
SKDF7sz_wgI-004|So let's take sulfur, chlorine, and potassium and ask, which has the lowest atomic radius?
SKDF7sz_wgI-008|We're trying to deduce atomic radius from other properties that have periodic trends that we understand.
SKDF7sz_wgI-009|So we're taking sulfur, chlorine, and potassium-- three atoms.
SKDF7sz_wgI-026|So for smallest atomic radii, your best bet, chlorine.
JIKXNx5TK3Q-000|Let's look at two titrations-- the same acid, but tenfold diluted.
JIKXNx5TK3Q-001|So I'm going to take the weak acid, acetic acid, and titrate it with a strong base, potassium hydroxide.
JIKXNx5TK3Q-002|That is plotted here in the dotted yellow line.
JIKXNx5TK3Q-003|Then I'm going to dilute by a factor of 10 and reperform the titration.
JIKXNx5TK3Q-011|We're looking at titrating HAc, acetic acid, two times.
JIKXNx5TK3Q-012|One titration, then dilute by a factor of 10, and titrate again.
JIKXNx5TK3Q-013|Now, if you dilute by a factor of 10, the weak acid, initially, the pH will change by one unit because the H3O+ concentration changes by a factor of 10.
JIKXNx5TK3Q-014|But remember, in a weak acid, there's plenty of undissociated HAc around that will dissociate after that dilution and lower the pH.
JIKXNx5TK3Q-017|So the total amount of acid is the same, so the total amount of base required to reach equivalence point is the same.
JIKXNx5TK3Q-018|In the buffer region, remember, buffers are also resistant to changes in dilution.
JIKXNx5TK3Q-019|You dilute a buffer by a factor of 10, but the ratio of acid to base is what's important in a buffer.
DGTtekW_2J8-000|Let's look at a point on the titration curve.
DGTtekW_2J8-002|At point C, I've added one mole of my strong base for every mole of weak acid that I originally had.
DGTtekW_2J8-004|So what you have here is a solution of weak base.
DGTtekW_2J8-005|So you can calculate the pH here at point C by using a calculation of a weak base.
DGTtekW_2J8-006|Let's do that.
DGTtekW_2J8-007|Here's the weak base, in this case the conjugate base of acetic acid, reacting with water, because these are the two species left at the endpoint of the titration.
DGTtekW_2J8-008|They form the conjugate acid and OH minus.
DGTtekW_2J8-009|So at this point in the titration, we've titrated a weak acid with a strong base.
DGTtekW_2J8-010|At the endpoint, where I've used up all the acid, the solution is actually slightly basic.
DGTtekW_2J8-011|And it's slightly basic because I've converted all of the weak acid into its conjugate base.
DGTtekW_2J8-014|And I say, well, I have approximately 0.1 moles per volume.
DGTtekW_2J8-015|And the volume doesn't change much during a titration, because we can say we still have about 0.1 molar Ac ions.
DGTtekW_2J8-016|A little of that reacts to go back and form HAc and some OH minus.
DGTtekW_2J8-022|If I know HAc, I know Ka times Kb is Kw.
DGTtekW_2J8-023|So I can calculate a Kb.
DGTtekW_2J8-024|Kb is small.
DGTtekW_2J8-025|Kb is small, so I'll assume that 0.1 minus x is essentially 0.1, that x is small compared to 0.1.
DGTtekW_2J8-026|When I do that, the math gets relatively easy.
DGTtekW_2J8-027|x squared is 0.1Kb.
DGTtekW_2J8-028|So x is 7.5 times 10 to the minus 6.
DGTtekW_2J8-029|Now, x is the OH minus concentration.
DGTtekW_2J8-030|If I want the pH, I need the H3O plus concentration.
DGTtekW_2J8-031|And of course, I can get that because H3O plus and OH minus in water are always a product to 10 to the minus 14.
DGTtekW_2J8-032|So H3O plus times OH minus is 10 to the minus 14th all the time.
DGTtekW_2J8-033|That's an equilibrium that's holding.
DGTtekW_2J8-034|At the same time, this equilibrium is holding.
DGTtekW_2J8-035|So we satisfy them both at the same time.
DGTtekW_2J8-037|And in this case, the pH, 8.88.
DGTtekW_2J8-039|And if you have just weak base, the pH will be slightly basic.
w_9DNwm1DFI-000|Let's look at the amino acid cysteine at a specific pH.
w_9DNwm1DFI-001|So here I've drawn cysteine, and I've shown you the pKa's of each group.
w_9DNwm1DFI-002|So the pKa of this proton, the pKa of one of these protons, and the pKa of this proton.
w_9DNwm1DFI-003|The question is at pH 5, what's the overall charge?
w_9DNwm1DFI-004|So what are the protonation states?
w_9DNwm1DFI-005|Is the overall charge plus 1, 0, or minus 1?
w_9DNwm1DFI-012|We're looking at the amino acid cysteine at pH 5.
w_9DNwm1DFI-014|So, for instance, here the pKa is 9, so the pH is less than the pKa.
w_9DNwm1DFI-015|If the pH is less than the pKa, you're on the acidic side, so the acidic form predominates.
w_9DNwm1DFI-016|In fact, you're four units away from this.
w_9DNwm1DFI-017|So you're four units to the acidic side, so this is all in its acidic form.
w_9DNwm1DFI-019|Now here, pKa 8.
w_9DNwm1DFI-020|Again, the pH is 5, well to the acidic side.
w_9DNwm1DFI-024|Here, pKa 2.
w_9DNwm1DFI-025|This is the carboxylic acid part of the molecule.
w_9DNwm1DFI-026|The pKa is 2.
w_9DNwm1DFI-027|Now, I am on the basic side.
w_9DNwm1DFI-028|The pH is 5.
w_9DNwm1DFI-029|The pKa is 2.
w_9DNwm1DFI-030|So I'm at a pH above the pKa.
w_9DNwm1DFI-031|On the basic side, so the basic form predominates.
w_9DNwm1DFI-032|The basic form is the form without the proton.
w_9DNwm1DFI-036|So in this case, the overall charge is 0.
w_9DNwm1DFI-037|Minus 1, plus 1, and 0 all sum to 0.
nbeE9b2JV5Q-000|Let's look at dissolving a solid.
nbeE9b2JV5Q-001|We'll have magnesium hydroxide, and we'll put it in water.
nbeE9b2JV5Q-003|Now, I'd like that to dissolve.
nbeE9b2JV5Q-004|What's the best strategy for dissolving that additional speck of magnesium hydroxide?
nbeE9b2JV5Q-005|Should I add 0.1 molar H2SO4, sulfuric acid?
nbeE9b2JV5Q-006|0.01 molar sodium hydroxide?
nbeE9b2JV5Q-014|We're dissolving magnesium hydroxide in water to form magnesium and hydroxide ions.
nbeE9b2JV5Q-015|Magnesium hydroxide, sparingly soluble, so the reaction favors the solid, and you can write the equilibrium expression.
nbeE9b2JV5Q-016|Magnesium ions and hydroxide ions squared, in this case, stoichiometric coefficient of 2.