CHEMISTRY COMMUNITY

ian_haliburton_1f

The intermediate will appear only in the elementary reactions (steps of the proposed reaction mechanism) but will cancel out when you write the overall balanced reaction. They are products of an elementary reaction that are fully used up as reactants in a subsequent elementary reaction.

ian_haliburton_1f

Platinum is written in the cell diagram to indicate that a solid platinum electrode is needed to recreate a working cell. This is needed when the anode or cathode of a cell doesn’t have any conducting substances in its composition. The platinum conducts the charge to create a current.

ian_haliburton_1f

The catalyst will appear from the beginning in the proposed reaction mechanism, but it will not appear in the overall equation because it will not be used up in the reaction and will therefore appear as both a reactant and a product in the elementary reactions, causing it to cancel out overall.

ian_haliburton_1f

Does anyone know the term for when 4 molecules are required to collide? In other words, what comes after termolecular?

ian_haliburton_1f

Can someone explain to me why the slowest step in a reaction process determines the overall rate law for the reaction?

ian_haliburton_1f

Hi, I'm taking 14BL next quarter, and I was wondering what material from both 14A and 14B would be most beneficial for me to review over the break in preparation for the class?

ian_haliburton_1f

When there is a gas phase product in an open system reaction, is it safe to ignore the reverse reaction because the gas produced escapes and therefore does not react with the other products?

ian_haliburton_1f

Is there an easy way to tell when a chemical reaction has too high of an activation barrier to be kinetically spontaneous even though it is already known to be thermodynamically spontaneous?

ian_haliburton_1f

Does anyone know which specific differentiation and integration formulas/concepts I should review before we continue on with kinetics?

ian_haliburton_1f

The textbook has a side comment in the section about cell diagram notation that says “when it is important to emphasize the spatial arrangement of an electrode, the order may reflect that arrangement, as in Cl-(aq)|Cl2(g)|Pt(s).” I understand why the platinum is on the outside, but otherwise what ma...

ian_haliburton_1f

when you have the ln of something isolated on one side of your equation, you can solve for what’s inside the ln by taking both sides and “exponentiating” them. This means you write e^()=e^() with whatever was previously on each side of the equation in the parentheses. This works because e^(ln(x)) is...

ian_haliburton_1f

Going off of this, I was previously taught another set of acronyms for redox reactions.

LEO says GER
(Loss of Electrons-Oxidation), (Gain of electrons-reduction)
The professor already introduced the LEO part, but I feel like the GER (like the lions roar) goes with it nicely.

ian_haliburton_1f

Maybe it has to do with the fact that potential difference has to do with how positive one electrode is versus the other. When a stronger current of electrons flows, the positive electrode will attract them, which I would imagine effectively makes its charge more negative, thereby decreasing the pot...

ian_haliburton_1f

This comes from the fact that we're treating the gas as only being able to move in 3 directions. Its molecules can move in any direction x, y or z, so we write 3/2. We ignore the possibility that it has rotational or vibrational energy, which would make this coefficient higher. Dr. Lavelle just brou...

ian_haliburton_1f

For one thing, there are certain conditions under which gases do behave more like ideal gases and in those instances you would be able to perform calculations as we have been.For example, conditions of higher temp. and lower pressure contribute to more ideal behavior.

ian_haliburton_1f

Since this equation for entropy change is in the form ∆S=nCln(T2/T1), you could use the "heat equation" q=nC∆T to solve for C if you know q, which you would then use for the entropy calculation.

ian_haliburton_1f

What units (if any) do we use to measure entropy? Along those lines, do we write anything for units with degeneracy (W)?

ian_haliburton_1f

Yes, you are finding the heat capacity of the calorimeter, whereas that equation corresponds to molar heat capacity. As such, you can ignore the mass of the calorimeter and just use C=q/delta T

ian_haliburton_1f

Delta H equals qp for a system under constant pressure where the only work involved is the work of expansion. Since delta H is included for conditions in which there is usually work involved, it is more usual that delta U will equal delta H plus work.

ian_haliburton_1f

Generally speaking, are gases the most common subject of consideration in thermodynamics for chemistry?

ian_haliburton_1f

Since we can write the work function using an integral, does this mean there is some antiderivative equation that we can use to do straightforward integration?

ian_haliburton_1f

I believe that volume change in calculations of internal energy is only relevant to gas phase reactions. This is why work, which affects internal energy, can be written in a form that includes delta v, the change in volume.

ian_haliburton_1f

You calculate Q when you are not sure whether the reaction is at equilibrium. If you already know the reaction’s K value, you can use the same formula for K at any time, even when the reaction is not at equilibrium, and call the calculated value Q. Its value relative to K (whether it is less than K ...

ian_haliburton_1f

I believe that changing the volume of a container in which the reaction occurs would change the pressure (therefore pressure would not be constant) of the gases in said container according to the equation P=(nRT)/V.

ian_haliburton_1f

The term exothermic is used to denote reactions that release energy in the form of heat when they are carried out. Conversely, endothermic denotes reactions that require energy (which they acquire by absorbing heat from surroundings) to be carried out.

ian_haliburton_1f

Just showing your work is fine. Make sure to write down the question number though (e.g. 5C.1).

ian_haliburton_1f

Now that we are doing acid-base equilibrium, I was specifically wondering if anyone had a concise set of guidelines for identifying a weak base compared to a strong base as I am particularly foggy in my memory of that.

ian_haliburton_1f

I am fairly certain that this has to do with principles of thermodynamics that we will study later in the course.

ian_haliburton_1f

I believe you can also use other units for pressure (such as atm or Torr) as long as you adjust the value and units of the constant R accordingly? There is a table for values of R based on which units are used.

ian_haliburton_1f

The equation for the equilibrium constant, which is all we’ve been working with so far, can be derived to the same point using either a kinetic consideration or a thermodynamic consideration. There is a thorough explanation of what these both entail at the end of topic 5G, but I believe the technica...

ian_haliburton_1f

It is notation for standard pressure, which is 1 bar. It is included in the equation for the equilibrium constant only as a formality to make sure all the units cancel out.

ian_haliburton_1f

Is glucose a Bronsted acid considering that it contains several hydrogen ions? If so, is it a weak acid or a strong acid? Does this have anything to do with the condition ketoacidosis?

ian_haliburton_1f

Cations in these groups only have charges of 2+ or 1+, which is not often a high enough charge (unless you’re talking about transition metals with such charges) to break other molecules’ bonds and bond with them. For example, a sodium cation’s 1+ Charge is not enough to break oxygen’s bond with hydr...

ian_haliburton_1f

When coordinating, the oxygen in the water molecule is making three single bonds, making its formal charge already positive. It will not trade its remaining lone pair for another bond as its formalcharge would increase even more.

ian_haliburton_1f

Just out of curiousity, are there any coordination compounds that are critical to the functioning of the nervous system, just as heme structures are critical to the circulatory system?

ian_haliburton_1f

The textbook lists pentagonal bipyramidal as a possible molecular geometry, but I don’t believe that any of the examples we’ve done have had this shape. Is it super rare? What would be an example of a molecule with this shape?

ian_haliburton_1f

What is it, on a molecular level, that gives acids and bases their distinctive qualities. For example, what does the concentration of hydronium ions have to do with the sourness of acidic substances and what do hydroxide ions have to do with the soapy feel of bases?

ian_haliburton_1f

Will we need to know the nuances of what distinguishes induced dipole induced dipole, London dispersion force and Van Der Waals force? They were grouped together in the lecture.

ian_haliburton_1f

Will there be any calculation heavy elements to this third test as there was with the last two?

ian_haliburton_1f

Can we staple all 14 problems together or should we turn in two sets of seven, labeled separately as homeworks 8 and 9?

ian_haliburton_1f

Dr. Lavelle described a way to think about non polar molecules that doesn’t require drawing vector diagrams. I remember something about interactions with an electric field, but otherwise the concept was lost on me. I would appreciate if someone could elucidate this.

ian_haliburton_1f

We talk about dipoles as a way to explain the differences in charges between parts of a molecule relative to the distance between them. This is used to illustrate that there is a subtle distortion/ attraction of electrons towards whatever part has a partial negative charge.

ian_haliburton_1f

Numerically speaking, have you checked to see if the difference is greater than 2? Otherwise there’s a good deal of room for ambiguity that can only be resolved experimentally.

ian_haliburton_1f

In lecture last week, Dr. Lavelle pointed out two molecules that have the same molecular formula but are referred to by different names because they have different shapes. How would one differentiate between two possibilities when the formulas are the same?

ian_haliburton_1f

Can anyone recommend an interactive online resource for visualizing different molecular shapes in 3D?

ian_haliburton_1f

When the midterm is returned, will there be comments on any portions where we lost points so that we can consider what we did wrong?

ian_haliburton_1f

The reasons for both cases have to do with formal charges. For b), Phosphate has 5 valence electrons, so you're trying to get the formal charge to equal 5 minus 5 in some way. In the structure of the Hydrogen phosphate ion, Phosphate achieves a formal charge of zero by making 5 bonds. If it were to ...

ian_haliburton_1f

The 6s electron is still the most energized in the atom, and it is furthest away from the nucleus, being the only n=6 state electron. So, it will be easiest to separate from the atom altogether.

ian_haliburton_1f

It is because radicals are so unstable that they will only exist for a very short time before reacting with something else in an effort to regain stability. This intense reactivity is what makes them dangerous to things like the body's cells, for example.

ian_haliburton_1f

Is it correct that the values of the quantum spin number have nothing to do with the wave function? I remember the later experiment with electrons and magnetism described in the text, but how is the value 1/2 derived?

ian_haliburton_1f

Will we be drawing line structures in this course as well? Regardless, what is the benefit of each system for representing bonds compared to the other?

ian_haliburton_1f

This is because until it has a pair of electrons occupying it, the 4s orbital actually has less energy than the 3d orbitals. So, elements whose outermost electrons are in 4s (Potassium and Calcium) occur in the table before any of the 3d elements. To include the 3d elements in the same period as 3s ...

ian_haliburton_1f

The asymmetry is a way of describing that there are certain spaces in the atom where it would be more likely to find an electron.

ian_haliburton_1f

The equation from the book that you’re referencing uses the constant “h bar”(the typical h but with a line trough the stem of it) h bar is equal to h/2(pi). So when you substitute this you get the familiar h/4(pi).

ian_haliburton_1f

Dr. Lavelle stated that he will follow the convention that -1 corresponds to Px, 0 to Py and 1 to Pz.

ian_haliburton_1f

I have heard that these sessions are helpful if you would benefit from additional structured review time on top of discussions. They can also be easier to access than office hours.

ian_haliburton_1f

Certain amounts of energy from incoming photons will excite the electrons and cause them to move to higher energy levels. Beyond a certain point, however, the electron can move far enough away from the positive nucleus that the attractive force can no longer keep it in orbit. It is when there’s enou...

ian_haliburton_1f

If you are working through problem L.35 in the 7th edition, be advised that your copy (like mine) may contain a typo in the question. Namely, the third equation’s reactant should be Fe3Br8 instead of FeBr2, as the three equations are supposed to represent a series of reactions.

ian_haliburton_1f

For this question, as you are given the total mass of the compound, you do not need to concern yourself with mass percentage composition. Rather, you can divide the actual available masses of the elements by their molar masses to find how many moles of each there are. This is the first step that the...

ian_haliburton_1f

When solving for a value using this equation, you will need to know three other values already. So, one of the known values needed to solve will always be a concentration. This value is given in terms of moles per liter, so any other values in terms of mililiters to the equation would be off the sca...

ian_haliburton_1f

In the practice problem set of Fundamentals E, there is a question (E15) that requires knowledge about metal hydroxides and sulfides. It seems that if you are given a metal hydroxide’s formula, you can derive a corresponding sulfide through the hydroxide’s molar mass. I am not sure how and why works...

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