CHEMISTRY COMMUNITY

Christy Lee 2H

At the end of class

Christy Lee 2H

An activated complex is like a transition state, so you would draw out a transition state for the molecules.

Christy Lee 2H

For reversible reactions, deltaS total is 0. For perfect crystals, entropy is 0 at 0K.

Christy Lee 2H

Christy Lee 2H

It has to be a multi-step reaction where a fast step comes before a slow step.

Christy Lee 2H

We only need to do pre-equilibrium approach. We won't be doing the steady state approximation.

Christy Lee 2H

For this question, why can we assume that the temperature is 298 K?

Christy Lee 2H

Does adsorption only happen for a heterogeneous catalyst?

Christy Lee 2H

Does what you described have to do with the frequency factor at all?

Christy Lee 2H

Do you know where A went though?

Christy Lee 2H

He said whatever is discussed in lecture will be on final.

Christy Lee 2H

Only the functional groups in class. He said these are the most common.

Christy Lee 2H

I believe in can be in the rate law.

Christy Lee 2H

Since we went over Sn2 reactions in class, I think some ochem will be on the final.

Christy Lee 2H

The direct computation method has a lot of advanced math that computers do, so we will not use it. We only need to know how to do the pre-equilibrium method which is where a slow step causes a bottleneck of the products from the step before, creating a pre-equilibrium.

Christy Lee 2H

We do not need to know how to do the steady state approximation, but we do need to use pre-equilibrium conditions (both should give the same answer).

Christy Lee 2H

Since rates are always positive values, the rate constant k is always positive.

Christy Lee 2H

Does this mean that radioactive decay only works for a reaction if there's one reactant since it's a first order reaction?

Christy Lee 2H

Yes! They're the same.

Christy Lee 2H

Writing rate laws means using concentration of the reactants and a rate constant k. You will have to determine the order of each reactant to get the exponent and if it is 0 order, that reactant won't show up.

Christy Lee 2H

Usually platinum is used as an inert metal electrode.

Christy Lee 2H

Comma is for same phase and solid line is for different phase.

Christy Lee 2H

As long as solids are on the outsides, it does not matter.

Christy Lee 2H

The electrode is the solid metal that conducts electricity, and the electrolyte is the aqueous solution with ions.

Christy Lee 2H

When the redox reaction has no solid that can act as the electrode, you will need a platinum electrode.

Christy Lee 2H

For this problem the cell diagram in the solutions manual divides Ag(s) and AgBr(s) on the anode side with a vertical line. Can someone explain why they aren't separated by a comma even though they're the same phase?

Christy Lee 2H

Both allow exchange of counter ions to maintain the charge difference while separating the atoms or elements that are actually involved in the redox reactions.

Christy Lee 2H

I think that Ecell when we calculate it represents the maximum potential difference. SInce this potential difference can be used like a battery, we are talking about the maximum possible difference, but real-world batteries would not actually produce this much voltage.

Christy Lee 2H

I think that since cell potential is also sensitive to the concentrations of reactants and products, you can set up a cell that will have a voltage difference because of differences in concentration. So even though both sides have the same molecule or element, the difference in concentrations will c...

Christy Lee 2H

It takes energy to break bonds (positive enthalpy) and releases energy to form bonds (negative enthalpy) and then you add those enthalpies together. You could also do broken-formed but make sure you use bond enthalpies directly.

Christy Lee 2H

For a reversible process, the reaction is assumed to be at equilibrium which means deltaS of the universe is zero because there is no entropy change at equilibrium.

Christy Lee 2H

Negative delta G is spontaneous because free energy goes from a higher energy state to a lower energy state which is favorable.

Christy Lee 2H

Lavelle's formula sheet gives the approximation for monatomic ideal gases only, which is why it says 3/2R. For diatomic ideal gases, the approximation is 5/2R.

Christy Lee 2H

I think for the first part of the problem we have to use nR but the second part is the one where we have to use C. And on the solution errors page it says to use Cv but it also says 5/2R

Christy Lee 2H

How do we know whether to use Cv or Cp though? I thought the volume and pressure were both changing???

Christy Lee 2H

Can someone please explain why pressure decreases in a reversible pathway? I'm confused by the graph that was in the notes comparing reversible and irreversible pathways. Thanks!

Christy Lee 2H

Can someone explain the difference between $S=k_{b}lnW$ and $k_{b}ln2$ ?

Christy Lee 2H

Why is enthalpy a state property and heat not a state property?

Christy Lee 2H

Can someone explain why P delta V is insignificant when there's a reaction with constant P that involves solids and liquids? Thanks!

Christy Lee 2H

My TA mentioned this during discussion, but can someone explain what adiabatic means?

Christy Lee 2H

Can someone explain the difference between reversible and irreversible reactions?

Christy Lee 2H

Why does the temperature stay the same during phase changes?

Christy Lee 2H

What's the difference between bond enthalpies vs standard enthalpies of formation?

Christy Lee 2H

Can someone explain me how ∆Hsub= ∆Hfus+ ∆Hvap?

Christy Lee 2H

CaO is a strong base, so it dissociates into Ca2+ and O2-. The O2- accepts a proton from water to form OH-. Since this creates a basic solution, CaO is a base.

Christy Lee 2H

Metal oxides tend to be bases, while non-metal oxides tend to be acids. There is a diagonal band similar to the metalloid band and those oxides are amphoteric. I think you can find that in the textbook.

Christy Lee 2H

I think only digits after the decimal place are considered significant. For example, pH of 4.23 would be 2 sig figs.

Christy Lee 2H

In lecture, Dr. Lavelle said "almost always" so there are probably some exceptions. For example, autoprotolysis where water acts as an acid and a base does not produce a salt. But for the most part, acids and bases will react to form salt and water.

Christy Lee 2H

In endothermic reactions, heat is consumed or absorbed to move the reaction forward. In exothermic reactions, heat is released or given off. You can think of endothermic reactions as having heat as a reactant, whereas exothermic reactions have heat as a product.

Christy Lee 2H

It is not on the syllabus or any of the outlines or homeworks, so we do not need to know it for the final:)

Christy Lee 2H

Bronsted vs Lewis definitions are just focusing on different aspects of the molecule to determine acidity and basicity. Using either definition will lead to the same answer. For example, a Lewis acid is the same as a Bronsted acid, but if you say Lewis acid you are focusing on the ability of the mol...

Christy Lee 2H

It might help to draw it out, but in general, I usually look for nitrogens with lone pairs and oxygens with a negative formal charge because these most commonly act as binding sites in coordination compounds. Then I count how many there are, and that is how I determine what kind of dentate it is. Ho...

Christy Lee 2H

How do I know when to use partial pressure or concentration when calculating the equilibrium constant?

Christy Lee 2H

Why are ligands Lewis bases?

Christy Lee 2H

How do hybridized orbitals relate to sigma and pi bonds?

Christy Lee 2H

How do I know when dipole moments cancel?

Christy Lee 2H

Yes I got that too.

Christy Lee 2H

Polarizing power and polarizability are opposites. Polarizing power refers to the cation's ability to pull electrons toward it, so when the atom is smaller, there are less electrons, so the anion will be closer to the nucleus and feel a stronger pull. Polarizability is how easily an atom's electron ...

Christy Lee 2H

Why don't Lithium and Beryllium have full octet when drawing Lewis structures?

Christy Lee 2H

You would have to calculate what exactly 1% of the hydrogen radius is, and then use that as your deltaX (uncertainty in position) in the Heisenberg uncertainty formula. Then you would solve for deltaV which is the uncertainty in velocity. Hope this helps! :)

Christy Lee 2H

For the nitrate example, any of the three resonance structures are correct if the questions just asks for a lewis structure. However, we just have to understand that the real structure is a blend of the three. For other examples though, we would have to look at formal charges to determine which is t...

Christy Lee 2H

Nuclear charge plays a role because higher nuclear charge will have a greater pull on electrons which means higher electron affinity, which is why electron affinity increases going across a row. The almost-full valence shell is another way of thinking about it, because atoms want to have noble gas c...

Christy Lee 2H

Can you clarify the difference between shells and subshells?

Christy Lee 2H

Can someone explain why s-electrons have a lower energy than p-electrons? Confused because their energy differs even though they're in the same shell??

Christy Lee 2H

I am pretty sure Dr. Lavelle said we would not be covering black bodies, so you will not need to know Wien's law or Stephen Boltzmann law.

Christy Lee 2H

I believe the way light reflects, refracts, diffracts, and interferes all point to its wave-like characteristics.

Christy Lee 2H

When doing the work for some of the problems, it will be necessary to change units to kilograms depending on what units the constants have that you use in your equations. But for finals answers, you can leave your answer in grams or kilograms as long as you have the right sig figs and right conversi...

Christy Lee 2H

I think that only very very small objects have wavelike particles, and when they get too big, the wavelike properties are basically negligible, which is why they say electric cars would not have wavelike properties.

Christy Lee 2H

Yes they're the same thing

Christy Lee 2H

We will need to know what the prefixes mean so we can convert between them, like knowing that 10^12 picometers are in one meter. These conversions will not be given, so we have to remember what each prefix means. Hope this helps!

Christy Lee 2H

In a multistep problem, should we use sig figs with every step, or only when it comes to the final answer? Will we be penalized if we use more than the amount of sig figs in intermediate steps but have the correct amount for the final answer? I am pretty sure we are supposed to only use sig figs in...

Christy Lee 2H

It should come out to a whole number when you are trying to find out what to multiply the empirical formula by in order to get the molecular formula. Otherwise, there might have been a calculation error. Hope this helps! :)

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