CHEMISTRY COMMUNITY

Rebecca Epner 4A

Amphiprotic means that a substance can both accept and donate a proton or H+. Amphoteric means that a substance can act as both an acid and a base. All amphoteric substances are amphiprotic because if a molecule can either donate or accept a proton, that means it can act as both an acid or a base. ...

Rebecca Epner 4A

They have both basic and acidic character, meaning that they can react with bases and acids. The elements around the diagonal line of metalloids typically form amphoteric oxides (such as BeO, Al2O3, Ga2O3)

Rebecca Epner 4A

The central component of hemoglobin, heme, is chelating. This is also called the porphyrin ligand. (We drew a picture of it in lecture)

Rebecca Epner 4A

Can someone simply post the equations we need to know for acid rain?

Rebecca Epner 4A

Why does each subsequent Ka value decrease significantly? In class I wrote Ka1 > Ka2 > Ka3 because it is harder to lose H+ from a negatively charges ion but can someone explain this further?

Rebecca Epner 4A

Is water both amphoteric and amphiprotic?

Rebecca Epner 4A

H2O is the best reactant to choose because it is also amphoteric, meaning that it can act as both an acid and a base so it works in both equations.

Rebecca Epner 4A

I just read on a different post that you must write anion ligands before neutral ligands so just make sure to do that as well.

Rebecca Epner 4A

Is the best way to determine if a ligand is polydentate to draw its structure? Or is there some trick to memorize or understand to make this quicker and easier?

Rebecca Epner 4A

In polyphonic reactions protons are lost successively. So several reactions occur one after another and a single proton is removed in each one.

Rebecca Epner 4A

I think a lot of the time the question will identify if it is strong or weak for you (at least all of the textbook problems do this). But in general stronger acids have a lower pH than weak acids because the bonds in a strong acids are weak which means they can more easily lose H+

Rebecca Epner 4A

Are all polydentate ligands chelating ligands? What if a ligand has multiple binding sites but is unable to form a ring? Or is that not a possibility?

Rebecca Epner 4A

A chelating complex contains one or more ligands that forms a ring of atoms that includes the central atom. A common example is edta (which we viewed in class). It can form strong complexes with many different metal ions.

Rebecca Epner 4A

Can someone simply explain how to calculate the oxidation number? I can't find a clear explanation in the book.

Rebecca Epner 4A

The first thing to remember is that all the ligands are written in alphabetical order, followed by the name of the transition metal cation, and then the Roman numeral which is the oxidation number of the metal. I start by looking at the ligand, determining the Greek prefix and name. For example, in ...

Rebecca Epner 4A

How do you determine if a ligand can be polydentate?
For example, question 9C.5 asks to determine if the following ligand is polydentate, and if so, give the maximum number of places on the ligand that can bind simultaneously to a single metal center.
HN(CH2CH2NH2)2

Rebecca Epner 4A

The book says it is impossible to predict the extent of distortion of bond angles when lone pairs are present. The only way to determine the value would be to measure it experimentally or calculate it with the Schrodinger eqn (which we don't have to do)

Rebecca Epner 4A

This is a list from my TA: -VSEPR (determining shape) -Use dipole moments to determine if polar or non polar -use shame and polar/nonpolar to identify intermolecular interactions -explain why lone pairs are more likely found in certain locations around central atom and how/why they affect bond angle...

Rebecca Epner 4A

Why are lone pairs more likely to be found in certain locations around a central atom? And which locations are these?

Rebecca Epner 4A

I know we have to know the difference between sigma and pi bonds. I'm pretty sure I heard Dr. Lavelle say hybridization will not be on the test but I'm not sure. Here is a list of topics from my TA: -VSEPR (determining shape) -Use dipole moments to determine if polar or non polar -use shame and pola...

Rebecca Epner 4A

Ions have either more electrons (anion) or less electrons (cation) than its original atom. The electron configuration represents this by either adding or removing electrons from the outermost orbital.

Rebecca Epner 4A

Since, as stated above, the atomic radius of a larger atom is so big, its shape can become more easily distorted, meaning it is highly polarizable.

Rebecca Epner 4A

If a molecule is made up of two other same atoms, the molecule is nonpolar because the electronegativities are the same. Also, be sure to note that the bonds within a molecule may be polar even though the overall molecule is nonpolar.

Rebecca Epner 4A

All of the above are great explanations. We denote dipole moments by drawing an arrow from the more positively charged atom pointing to the more negatively charged one.

Rebecca Epner 4A

They are the same. Both names were included under the list of interchangeable names for induced dipole-induced dipole

Rebecca Epner 4A

In general, bases donate electrons while acids accept electrons

Rebecca Epner 4A

Polarizability also explains the likelyhood of a certain atom to become distorted. This is why larger atoms have a higher polorizability

Rebecca Epner 4A

Why is the energy of an atom not increased when electromagnetic radiation is emitted from it?

Rebecca Epner 4A

Why are the units for kinetic energy and ionization energy different?

Rebecca Epner 4A

This isn't specific to indeterminancy, but can someone list which equations are allowed to be used for photons and which can be used for electrons?

Rebecca Epner 4A

Do you always have to compute formal charge when drawing Lewis structures?

Rebecca Epner 4A

Can someone explain why some elements can bond with others to obtain more than 8 valence electrons? And which elements are these?

Rebecca Epner 4A

Why is it important to first write the ground state electron configuration of an element before determining the electron configuration of an anion or cation?

Rebecca Epner 4A

I know ionic and atomic radius follow the same trend in the periodic table increasing down the group and decreasing across a period, but does the covalent radius also follow this trend? Lavelle mentioned it in class but I was confused about the trend it follows. I believe covalent radii follow the ...

Rebecca Epner 4A

When I try to picture this, it's also helpful to remember that each subshell has an increasing number of orbitals and can therefore hold an increasing amount of electrons. So 3s can only hold 2 electrons since it only has one orbital. But 3p has three orbitals and can therefore hold up to 6 electrons

Rebecca Epner 4A

From what I could gather, he recommended writing the configuration in this way if not all the orbitals are filled just so we could better visualize how electrons are paired with one another. I think it explains the reasoning behind this in the book a little more if you want more info

Rebecca Epner 4A

What makes the second ionization energy of any given element consistently much higher than the first?

Rebecca Epner 4A

And as a follow-up to my previous question, why are Cr and Cu exceptions to the 4s before 3d rule?

Thanks in advance

Rebecca Epner 4A

Can someone explain exactly why in some instances 4s come before 3d? And in what cases does this occur?

Rebecca Epner 4A

I remember Dr. Lavelle saying we won't go into very much depth concerning black body radiation but are there key points I should know and understand?

Rebecca Epner 4A

Can someone explain how you will know when to use which equation? What should I look out for in the context of the problem to determine which equation is most appropriate?

Rebecca Epner 4A

For this problem, you are expected to know the masses of both a proton and a neutron (you can probably find them in the chapter). Then substitute these values into the de Broglie relationship to calculate both wavelengths (they should be equal for 3 sig figs)

Rebecca Epner 4A

You should use the de Broglie relationship to find the wavelength. lambda=h(mv)^-1

Rebecca Epner 4A

In order to use the de Broglie relationship, you first need to put m in terms of m.s^-1. Then you can solve for the wavelength by using Plancks constant and the known mass of e-

Rebecca Epner 4A

I've been told the questions consist of some math questions similar to those in the homework as well as some short conceptual questions that were mostly covered in lecture. So to answer your question, no I don't think we are expected to know that yet.

Rebecca Epner 4A

I asked this question in a Step up session today and the UA told me that in most problems where we have to write chemical equations, the state will be explicitly given. But if it is not just try your best to guess because it may be worth a very small amount of points

Rebecca Epner 4A

Just a quick tip: if the numbers don't seem obvious or you can't seem to make the equation work, try using a system of equations

So (A)Fe3O4 + (B)CO = (C)Fe + (D)CO2
and then proceed to solve for each element
Fe: 3A=C
O: 4A=B+2D
C: B=D

Rebecca Epner 4A

I believe in some cases formula units refers to the number of atoms while in other cases it refers to the number of molecules, just depending on what the specific question is asking

Rebecca Epner 4A

Today in my Step-up session I was told to use the units that logistically make the most sense for the problem (which will usually be g, L, etc) but it is important to have the knowledge of how to convert between the different units in case it is necessary for a specific question.

Rebecca Epner 4A

But is it possible if there are at least 3 reactants and 2 of them (the limiting ones) are equal?

Rebecca Epner 4A

These are all different units. I actually don't quite understand the difference between g.mol and g.mol-1 (so far I think we've only used g.mol-1). Mol=moles as in the number of atoms in exactly 12g of carbon-12 (6.022 x 10^23 units of whatever you're measuring). g.mol-1 is the notation for grams pe...

Rebecca Epner 4A

All of the above are true. Just be sure to remember that dilution does NOT change the moles of solute in the solution, only the overall volume

Rebecca Epner 4A

Can someone explain the following problem? According to the following equation, 0.750 g of C6H9Cl3 is mixed with 1.000 kg of AgNO3 in a flask of water. A white solid, AgCl, completely precipitates out. What is the mass of AgCl produced? C6H9Cl3 + 3AgNO3 ---> AgCl + C6H9(NO3)3 I found the molar masse...

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