CHEMISTRY COMMUNITY

Cassidy Kohlenberger 3D

To what extent do we need to have an understanding of acid rain? Do we need to know the chemical formula

Cassidy Kohlenberger 3D

Can someone explain why the nitro groups on thymine are amphiprotic? And how would you write proton transfer equilibria equations with these groups?

Cassidy Kohlenberger 3D

I know that in AlCl3 and Cu(NO3)2, the Al3+ and Cu2+ are highly charged metal cations, and their pull allows water molecules to pick up another H+ and therefore make the solution more acidic. However, I'm really struggling on writing out equations to demonstrate this. For example, in the solution gu...

Cassidy Kohlenberger 3D

When determining the relative strength between 2 acids, are you supposed to compare the bond length and anion stability of their conjugate bases? Or the compound as is?

Cassidy Kohlenberger 3D

I have read through the textbook and I'm still a little confused on how to determine whether a compound is a Lewis acid or Lewis base. I know a Lewis acid is an electron acceptor and a Lewis base is an electron donor, but I'm not quite sure how to look at a compound and determine this. Is it based o...

Cassidy Kohlenberger 3D

In homework problem 9C.5, (CO3)2- is revealed to be both monodentate and bidentate. Can someone explain how this is possible? Also, are there any other ligands that fall under this category we need to know?

Cassidy Kohlenberger 3D

In homework problem 9C.5, (CO3)2- is revealed to be both monodentate and bidentate. Can someone explain how this is possible? Also, are there any other ligands that fall under this category we need to know?

Cassidy Kohlenberger 3D

The definition of a chelate as given in lecture is that it is a complex containing a ligand that forms a ring of atoms that includes the central metal atom. I don't understand how to apply this definition to the homework problems. If a ligand is polydentate, does that mean it is a chelating ligand? ...

Cassidy Kohlenberger 3D

Question 9C.9 in the textbook homework is related to determining a metal ion's coordination number. For part (c), en is bidentate, causing the coordination number of the complex to be 6. For part (d), edta is hexadentate, causing the coordination number of the complex to be 6. How and why does a lig...

Cassidy Kohlenberger 3D

When doing the homework and referencing the charts in the textbook, it is evident that water is monodentate even though the oxygen in it contains two lone pairs. Is determining if a ligand is mono, bi, or polydentate directly related to the number of lone pairs it contains? If it is related to lone ...

Cassidy Kohlenberger 3D

Can someone explain/summarize what we need to know about Bronsted acids? I was kinda confused when he went over them in lecture on Friday.

Cassidy Kohlenberger 3D

Because conceptual questions are included in Lavelle's midterms and final, it would definitely be helpful to know the biological examples/functions of the transition metals he went over in class. I don't think he'd test us on an obscure example he didn't go over in depth.

Cassidy Kohlenberger 3D

Can someone explain how the concept of chelates could show up as a problem on the test?

Cassidy Kohlenberger 3D

I believe it has a -2 charge

Cassidy Kohlenberger 3D

Can someone explain what it means for a transition metal complex to be organometallic?

Cassidy Kohlenberger 3D

In question 3F.19 in the textbook, part b asks you to explain why the vapor pressure of diethyl ether (C2H5OC2H5) is greater than that of water. What is the correlation between vapor pressure and boiling point? Also, in part c, it asks you to explain why the boiling point of pentane, CH3(CH2)3CH3, i...

Cassidy Kohlenberger 3D

On part (c) of 3F.5 in the textbook, it asks if CHI3 of CHF3 has a higher boiling point. I assumed it was CHF3, as there is a larger difference in electronegativity between C and F than C and I, therefore the bonds would be stronger and harder to boil in CHF3. However, the answer key says that CHI3 ...

Cassidy Kohlenberger 3D

On part (c) of question 3F.3 in the textbook, it asks if there are dipole-dipole interactions in the molecule CH2Cl2. Drawing out the Lewis structure, it appears as though the dipoles cancel each other out, yet the answer key says the molecule contains dipole-dipole interactions. I think it might ha...

Cassidy Kohlenberger 3D

If a question asks which molecule has the highest boiling point, find out what type of bonding is within each molecule. The strongest are ionic bonds (ion-ion), then ion-dipoles, then hydrogen bonds, then dipole-dipoles, then LDF. The stronger the bond, the higher the boiling point.

Cassidy Kohlenberger 3D

An example of an ion-ion interaction is NaCl, as this is ionic bonding (their charges cancel). An example of an ion-dipole interaction is when Na bonds to a water molecule, as Na is the ion and there are dipole interactions between the O and H in the water molecule. An example of a dipole-dipole int...

Cassidy Kohlenberger 3D

test 2 isn't cumulative right? Is it only based on material covered after the midterm?

Cassidy Kohlenberger 3D

I'd recommend doing problems from the 3F section on the chemical bonds outline as those were not covered on the midterm :)

Cassidy Kohlenberger 3D

As all these elements are located in period 3, they can have expanded octets through using their energetically accessible, low-lying d sub-shell for bonding. This is why period 2 elements cannot have an expanded octet, as they don't have access to the d sub-shell.

Cassidy Kohlenberger 3D

Yes! Lewis acids accept electrons whereas lewis bases donate electrons. We will definitely elaborate more on them in the future weeks remaining in the quarter

Cassidy Kohlenberger 3D

Hybridization is a concept where atomic orbitals can fuse to form new, hybridized orbitals. Basically, it's an expansion of the valence bond theory, which assumes all bonds are localized bonds formed between two atoms due to each one donating an electron. In terms of determining hybridization, here'...

Cassidy Kohlenberger 3D

How is it possible for ionic compounds to have covalent properties? I know it's possible, but I don't know how to explain the concept in a way that makes sense.

Cassidy Kohlenberger 3D

In addition to referring to the electronegativity, I would look at the compound to see which atom is more likely to form bonds. For example, carbon forms four, nitrogen three, oxygen two, etc.

Cassidy Kohlenberger 3D

Personally, I like to draw out the Lewis structure with single bonds first, fulfilling the octet rule for the atoms if possible. Then I calculate formal charge: a quick way to do this is by drawing a circle around the atom (basically splitting the bonds in half) and counting how many electrons it ha...

Cassidy Kohlenberger 3D

What is the difference between an element that does not have to satisfy the octet rule, and an element that can have an extended octet? I think, I might be wrong, that all elements group 3 and below can have an extended octet?

Cassidy Kohlenberger 3D

Electronegativity describes the tendency of an atom to attract a shared pair of electrons. Electron affinity, simply put, is how badly an element "wants" an electron to make it more stable. They can both be followed by the same trend: they increase going up groups and right across periods.

Cassidy Kohlenberger 3D

I don't believe we have to do calculations however I'm not 100% sure. What he will most likely do is present us with several elements and ask which one has the highest or lowest electron affinity. So basically...interpreting/applying your knowledge of periodic trends.

Cassidy Kohlenberger 3D

A half-full or completely full d sub-shell is more stable than a full 4s orbital. "Removing" the electron from the s sub-shell and placing it in the d sub-shell is actually when an electron becomes excited with more energy so it can move up a level.

Cassidy Kohlenberger 3D

They are exceptions because a completely full or a half full d sub-level is more stable than a partially full d sub-level. To make the d sub-level more stable, an electron from the 4s orbital is excited/rises to the 3s orbital. Instead of 3d^4 or 3d^9, we excite an orbital to make 3d^5 of 3d^10.

Cassidy Kohlenberger 3D

How familiar with the f-orbital do we need to be for the midterm? Will we be doing electron configurations for elements that include the f orbital?

Cassidy Kohlenberger 3D

Use periodic trends! The atom with the lowest ionization energy takes the least amount of energy to remove a valence electron from its outer shell. Ionization energy increases from left to right across a period and decreases going down a group. This is because a larger atomic radius means the valenc...

Cassidy Kohlenberger 3D

Elements of the s-block have much lower ionization energies than p-block metals. Therefore, it doesn't take much energy for them to give away electrons, so s-block metals usually form cations. This tendency to form cations makes the s-block metals more reactive. Hope that helped :)

Cassidy Kohlenberger 3D

This is due to the Pauli-exclusion principle. Also, it's important to note that an orbital can only contain a maximum of 2 electrons, so the two electrons must have opposing spins.

Cassidy Kohlenberger 3D

As frequency decreases, wavelength increases. As wavelength increases, the slope of each wave decreases as the waves appear less steep. Slope = extent of change, therefore the extent of change decreases. Also, it always helps me to draw it out :)

Cassidy Kohlenberger 3D

The n levels are principal energy levels that are very important to know in order to do Rydberg equation problems. The change in energy is the energy of the final level minus the energy of the initial, solved by substituting in the Rydberg equation. You use the quantum number of the energy level in ...

Cassidy Kohlenberger 3D

I'm not certain but you could always ask Dr. Lavelle after his lecture. A similar way to study is by using Khan Academy. There are videos on almost every topic we've covered and quizzes that correspond to them, just like Lavelle's modules.

Cassidy Kohlenberger 3D

The Lyman series requires the high energy of UV light. The Balmer series releases light in the visible region. Questions will assume you know this information when asking you to find the n levels (initial and final) of an electron. An example would be question 1A.15: In the ultraviolet spectrum of a...

Cassidy Kohlenberger 3D

Standing waves appear to be vibrating vertically without traveling horizontally. Here is a great khanacademy page that explains them/provides pictures!
https://www.khanacademy.org/science/ap- ... -review-ap

Cassidy Kohlenberger 3D

I think it just comes with familiarizing yourself with the compounds, but for some of them you can assume like H20 being liquid or if the problem tells you H20 vapor, then a gas. Diatomic elements like nitrogen, oxygen, hydrogen, etc. will be gases at room temperature. Usually compounds with oxide (...

Cassidy Kohlenberger 3D

The midterm is 2 hours long and the final is 3. Since discussions are only 50 minutes, I think they are altered to fit the allotted time to take the test during those weeks.

Cassidy Kohlenberger 3D

The lamda is a letter of the Greek alphabet that is used to represent wavelength (it looks like a squiggly v), whereas the lowercase v stands for frequency.

Cassidy Kohlenberger 3D

I'm not quite sure if we need to know those values by heart in Chem14A (I don't think we do) but they are very useful to know for the future! Plank's constant is 6.626 x 10^-34 J.s^-1 where J = m^2s^-2kg. Rydberg's constant is 1.097 x 10^7 m^-1. The speed of light (c) is equal to 299,792,458 m.s^-1.

Cassidy Kohlenberger 3D

I don't think we have to know polytatomic ions on the test as I believe the formulas will be given in the problems. However, they are very important to know for the future of this class. Here's a video on how to remember the most common ones :)
https://www.youtube.com/watch?v=zSqfwnkIkvQ

Cassidy Kohlenberger 3D

Ideally, yes, your answer should have the same number of sig figs as the values given in the problem. However, I asked my TA if on test one they were looking for the correct amount of sig figs in our answers and he said not to worry too much about it. As long as you know the concept and your answer ...

Cassidy Kohlenberger 3D

Regarding part b, we multiply by Avogadro's number to convert the moles we have into formula units. Since formula units are representative of molecules, we use Avogadro's number in the conversion. 1 mole = 6.022 x 10^23 molecules, atoms, formula units

Cassidy Kohlenberger 3D

I'd recommend balancing the simplest formula/element last. Most of the time this is hydrogen or oxygen. Also, writing how many moles of each element you have on both the reactant and product side can keep you organized when balancing the equation. There isn't a definitive way to balance equations, b...

Cassidy Kohlenberger 3D

Formula units are essentially empirical formulas for ionic compounds. It's the lowest whole number ratio of ions in an ionic compound. Most of the time formula units represent molecules, therefore they can be calculated by using Avogadro's number in a stoichiometric conversion. Hope this helps :)

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