CHEMISTRY COMMUNITY

SarahSteffen_LEC4

On question number 21 of the Marshmallow review. Why does iron have a +2 charge if two of the nitrogens on the porphyrin ligand have a +1 charge?

SarahSteffen_LEC4

What is the best way or method to determining if a polydentate is monodentate or polydentate?

SarahSteffen_LEC4

I thought HCN reacted with H2O to form CN- and H3O^+. So if this is the case, I'd say water is a base because it accepts a proton to form a Hydronium atom. But if it forms a hydroxide ion like you say, then it would be considered an acid, as it would donate one of its hydrogens to form the hydroxide.

SarahSteffen_LEC4

When I first approached this problem I was a bit confused. When looking in the solutions manual, they took the pKb of both morphine and BrO^- and compared the two. The one with the smaller pKb was the stronger base, which in this case happened to be BrO^- (hypobromite ion).

SarahSteffen_LEC4

Yes, this is the value that is always used because it is a constant.

SarahSteffen_LEC4

For part A, trichloroacetic acid is a stronger acid than acetic acid because the CCl3 group bonded to the carboxyl group is more electron withdrawing than the CH3 group bonded to the carboxyl group in acetic acid. For part B, formic acid is a bit stronger than acetic acid because the CH3 group bonde...

SarahSteffen_LEC4

For part A, the bronsted acid is HNO3 because it donates a proton to form NO3^-, and HPO4^2- is the bronsted base because it accepts a proton to become H2PO4^-. For part B, the conjugate acid to HPO4^2- is H2PO4^-, and the conjugate base to HNO3 is NO3^-

SarahSteffen_LEC4

Yes exactly. Only one lone pair will be able to bond at a time

SarahSteffen_LEC4

Are we expected to memorize that chart in our textbook that provides all the names when naming coordination compounds?

SarahSteffen_LEC4

For our final, are we going to have to know how to select the correct acid and base for an equation if a question asks us to "write a neutralization reaction that results in the formation of..."?

SarahSteffen_LEC4

I'm pretty sure that to determine whether or not atoms are in the same plane you have to see if there is the presence of a pi bond, which results from either a double or triple bond between atoms. Otherwise, if there is just a single bond/sigma bond, the atoms are free to rotate.

SarahSteffen_LEC4

The coordination number should be 6. I believe this is because the chloride ligands are monodentate while the ethylene diamine ligands are bidentate.

SarahSteffen_LEC4

My best bet is that it is simply put in that order for the chemical formula based off of alphabetical order.

SarahSteffen_LEC4

I believe you have to have the shapes memorized.

SarahSteffen_LEC4

Yes, you just want to draw the lewis structure that is most stable/least energy.

SarahSteffen_LEC4

i'm not completely sure, but I believe the rotating vs stationary polar molecules probably does have to do with whether or not there is just a sigma bond present or if pi bonds are also present.

SarahSteffen_LEC4

There is a permanent electric dipole moment pointing along the C-Cl bond, thus it is not induced.

SarahSteffen_LEC4

The T-shape allows the two lone pairs of electrons to be farthest apart if they occupy two of the three equatorial positions. If they were to occupy axial positions, there would be great repulsion by the electrons.

SarahSteffen_LEC4

Yes, that is exactly why 1 has a larger dipole moment than 2 in this problem.

SarahSteffen_LEC4

Typically, when do induced diple-induced dipole interactions occur/arise?

SarahSteffen_LEC4

I am unsure why the solutions manual to the midterm is using (9.109 X 10^-34 kg) when using the De Broglie Equation instead of using (9.109 X 10^-31 kg), which is what we've been using on homework problems for questions like these?

SarahSteffen_LEC4

That is probably primarily the interactions we should be studying and focusing on, but it's probably helpful to try and at least understand the various interactions in that section.

SarahSteffen_LEC4

I'm not certain but we probably just need to know why certain interactions have higher melting and boiling points than others and potentially be able to determine between two or more interactions which one would likely have the higher melting and/or boiling point.

SarahSteffen_LEC4

An important thing to note is that hydrogen bonds form when an H bonds to either an N, O, or F and there must be lone pairs available for the H to bond to. Thus, this can only be true for d (HNO2).

SarahSteffen_LEC4

In part B, since the bonds are the same, you have to look at atomic radius size to distinguish which bond is longer. Since phosphorus is larger than nitrogen, the PF bond should be longer than the NF bond.

SarahSteffen_LEC4

Do nonpolar molecules ever experience dipole moments or is it just for polar molecules?

SarahSteffen_LEC4

H2O contains hydrogen bonding, while C2H5OC2H5 only contains london dispersion forces. Therefore, C2H5OC2H5 contains weaker bonds than H2O and is thus not as tightly held together, allowing for a higher vapor pressure.

SarahSteffen_LEC4

I struggled on this question also, but now looking back at it, I think you would calculate the energy per photon required, using the equation E=hv or E=hc/lambda. And once you find that, I believe you would divide the energy that was given to you (in Joules) by the calculated energy you just found (...

SarahSteffen_LEC4

These series all of have the same energy level such as (n=1 or n=2).

SarahSteffen_LEC4

Well if you take the lewis structure of say a water molecule. The formal charges of the two Hs and the O are all zero, but a dipole moment still exists between the partial negative and partial positive charges.

SarahSteffen_LEC4

This is what I did to solve the problem but I keep getting an answer of 3.77 X 10^14 instead of 6.78 X 10^14 and I don't know why.

SarahSteffen_LEC4

Hi, can someone please go step by step through this problem and show calculations. I keep using De Broglie's formula and getting the wrong answer: A newly designed laser pointer with a certain frequency is pointed at a sodium metal surface. An electron is ejected from the metal surface with waveleng...

SarahSteffen_LEC4

When using the Rydberg Equation to find out the initial and final (n) values of energy for an electron during the emission of energy, is the equation: v=R[(1/n initial)^2-(1/n final)^2] or the opposite?

SarahSteffen_LEC4

I believe it just examines the absorption and emission patterns of molecules as opposed to just an atom.

SarahSteffen_LEC4

It is probably helpful to know them, but I feel that we will probably be given the formulas for solving problems. I'm not 100% sure though.

SarahSteffen_LEC4

When drawing Lewis Structures, how do we know when to use a double bond or triple bond vs just a single bond?

SarahSteffen_LEC4

I identify metalloids as the elements that fall into the diagonal zigzag on the right side of the periodic table. Metals are to the left of the zigzag, except for Hydrogen, and nonmetals are to the right of the zigzag.

SarahSteffen_LEC4

On this homework problem, we are asked to draw lewis structures for ion like the periodate ion and the hydrogen phosphate ion, but the problem doesn't provide you with any formula for these ions. So, I'm wondering whether or not we are expected to just know the formulas of these ions?

SarahSteffen_LEC4

When writing electron configurations it is okay to write [He]2s^2 2p^2 for carbon for instance, but conceptually you just need to know that electrons, when filling up the s, p, d, and f blocks do not want to be in the same orbital if possible. Thus, just think of the electrons as filling up the p-bl...

SarahSteffen_LEC4

In order to figure out which laser to use, you must solve for the energies of both the red ruby laser and the violet laser using the equation E=hc/lambda. Next you must convert the work function given in eV to joules. Once you have calculated all of these things, you look to see which of the two ene...

SarahSteffen_LEC4

I just placed the potassium atoms floating outside of/around the central phosphorous atom and then bracketed each atom to show the individual charges.

SarahSteffen_LEC4

I understand why Ionization Energy decreases down a group, but why does it increase across a period?

SarahSteffen_LEC4

What is the reasoning behind why the elements of Cr and Cu have different electron configurations than the rest of the elements in the 3d block? For instance why is Cr's electron configuration: [Ar]3d^5 4s^1 instead of [Ar]3d^4 4s^2?

SarahSteffen_LEC4

As you move from left to right across a period the nuclear charge of an atom increases, which trumps the shielding effect. Thus, ionization energy tends to increase across a period due to this increase in charge across a period.

SarahSteffen_LEC4

I am not exactly sure what units will be covered on the midterm, but anything we have learned or have gone over/will go over in class before the midterm I would say is fair game for a test question. From what I've heard, the midterm is similar in structure to our test, but with multiple different pa...

SarahSteffen_LEC4

I believe we can turn in quantum problems, especially since this Monday's lecture was still over quantum material. In addition, if he starts on a new focus topic, we can probably also submit problems under that.

SarahSteffen_LEC4

How do you determine what orbital an electron would be removed from to form a +1 ion for an element?

SarahSteffen_LEC4

How do you calculate the number of subshells present when given an n-value (for instance, n=6)?

SarahSteffen_LEC4

To calculate uncertainty, you would use Heisenberg's Indeterminacy Equation, which is delta p (indeterminacy in momentum)* delta x (indeterminacy in position)= h (planck's constant)/4pi. This equation is used because there is a limit on the accuracy to which momentum and position of a particle can b...

SarahSteffen_LEC4

In order to convert a number from meters to nanometers, you would utilize dimensional analysis and divide the number in meters by 10^-9 because that is the conversion factor. So you would divide (2.26*10^-46 m)/(1*10^-9) to convert from meters to nm. The good thing about conversionn/unit factors is ...

SarahSteffen_LEC4

I believe they multiplied that number by 10^3 because of the fact that it is keV, thus to get from keV to just eV you would need to multiply that number by 10^3.

SarahSteffen_LEC4

Say you are asked to calculate the frequency of a photon emitted by a hydrogen atom after making a transition from a higher energy level to a lower energy level. Well when using the Rydberg equation you would get a negative energy because energy is being emitted. But my question is could you get a n...

SarahSteffen_LEC4

Can someone please help me answer this question: Can atomic spectroscopy be used to identify elements? If so why is it possible?

SarahSteffen_LEC4

So I'm working on the quantum modules on the class website, and I need help with this question: The meter was defined in 1963 as 1,650,763.73 wavelengths of radiation emitted by krypton-86 (it has since been redefined). What is the wavelength of this krypton-86 radiation? To what region of the elect...

SarahSteffen_LEC4

The mass of ann electron is given on the formula sheet. So if you just pull out the formula sheet it should be there. It's probably helpful to learn, but I wouldn't worry too much because with all of our exams we are supposed to be given a formula sheet.

SarahSteffen_LEC4

When moving up energy levels, an electron absorbs energy (gains/increases in energy). If an electron falls down an energy level, it emits energy as a photon (loses energy).

SarahSteffen_LEC4

We are supposed to be provided with a formula sheet, but I would recommend learning the units just in case.

SarahSteffen_LEC4

By increasing intensity, more electrons may be emitted, but that does not mean that their energies have increased. Frequecy would need to increase for this to happen.

SarahSteffen_LEC4

No, you would not carry the two over to the next equation because this is a completely new equation. Thus, recommend writing the new equation out without any stoichiometric coefficients initially and then balance if needed.

SarahSteffen_LEC4

So what you want to do first is find the molarity of NH4NO3 after it has been diluted by using the equation (MiVi=MfVf). Thus, the diluted NH4NO3 solution concentration= (.2M x 1L)/4L=.05M. Next, you are going to find the number of moles present of NH4NO3 using only 100 mL. To find this, you would m...

SarahSteffen_LEC4

So I just worked out this homework problem without any problems, but my question is that on part B of the question it asks me to write the name of the oxide produced from a chemical reaction after finding the empirical formula. So my question is do we have to know how to name different oxides just b...

SarahSteffen_LEC4

So when I normally solve homework problems involving the molar mass of elements of compounds, I use all of the numbers given for each element (without rounding initially) to solve for a problem. But in the solution manual, sometimes I will get a different answer that is only off by a few decimal poi...

SarahSteffen_LEC4

When looking at the solution manual, I believe you must find the moles of tin and oxygen in their elemental form, which is why 16.00 g of oxygen is used as opposed to 32.00. And then with those moles, you would take the smaller of the two mole values and divide both by whatever the smallest number w...

SarahSteffen_LEC4

When given the correct balanced equation, I just look at the stoichiometric coefficients of whatever element(s) or compound(s) I am making a ratio for because those coefficients give the correct number of moles for that element or compound.

SarahSteffen_LEC4

Yeah, I personally try to use all of the digits given to me on the periodic table for an element/elements (specifically Lavelle's periodic table), and then I use as many steps as needed to solve the equation, without rounding whatsoever, until the very end, in which I will then round my answer as ne...

SarahSteffen_LEC4

So in the solutions manual for homework problems, what is the equation that was used with this: "V=(2.15*10^-3 mol Na+(1 mol NaCO3))/(0.07967 mol*L^-1 Na2CO3)(2 mol Na+)?

SarahSteffen_LEC4

I need help understanding part of the solving explanation on example problem G.2 in our chem textbook. The question states "Very dilute solutions of CuSO4 are used to control algal growth in fish tanks. Suppose you are investigating the optimum concentration that will control the algae but not ...

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