CHEMISTRY COMMUNITY

Connie Liang 3L

So would a standard enthalpy of formation encompass ALL the requirements that a standard reaction enthalpy would but also ADDS the condition that substances are forming from elements in their most stable forms?

Connie Liang 3L

Does standard enthalpy of formation by definition include that the reaction occurs at 1 atm and typically at 25 deg celsius? Or does that requirement only apply to a standard enthalpy reaction?

Connie Liang 3L

Thanks everyone for suggesting these alternatives! I will be sure to employ them :)

Connie Liang 3L

When doing the ICE box, is it your habit to put in moles or concentrations in? Is there a certain reason why you would choose one over the other?

Connie Liang 3L

Does anyone know if there's a reset button for Sapling so that after you finish a problem you can go back and redo the problem as if you haven't done it before? Just wondering to see if I can practice the assigned questions after I've completed them. Thanks!

Connie Liang 3L

Is my understanding correct that in acid/base reactions, autoprotolysis of water still happens because the overall acid/base reaction happens in water?

Connie Liang 3L

If in one reaction you have an acid ionizing and a base gaining a proton at the same time, why would you use Ka over Kb and vice versa?

Connie Liang 3L

I really like to make notes on the margins of HW questions I got wrong to make sure I understand why I got it wrong and to not repeat the same mistake again. Doing it in a different color really helps. Before tests, I'll go back and review the notes I made. Hope that's helpful!

Connie Liang 3L

I like watching cheesy romcoms! Some of my favorites are The First TIme and When in Rome. You can watch them full-length on YouTube for free with ads!

Connie Liang 3L

Thanks Nina, that was super helpful!

Connie Liang 3L

Understood, thanks for the replies everyone!

Connie Liang 3L

Pretty sure that since I is a larger molecule, the single bond representation is more accurate. I'm sure that having resonance structures combining would give us a bond length somewhere in between, but it might be because single bonds are longer and I is a larger molecule, and double bonds are shor...

Connie Liang 3L

The coordination number would be 6 because there's also an SO4 that needs to be accounted for. What helps me is counting up the number of molecules inside the coordination sphere (aka inside the brackets) other than the transition metal. That will be your number of ligands which is your coordination...

Connie Liang 3L

We don't have to know the specific angle. Knowing that it's less than 109.5 is enough.

Connie Liang 3L

Got it. I was confused because for other questions the answer had "less than" so I was wondering why didn't this one have it too. Thanks for clarifying.

Connie Liang 3L

How come in the answer manual the bond angles are approximately 120 degrees and 90 degrees and not less than 120 degrees and less than 90 degrees? Isn't a see saw shape supposed to mean that the bond angles are "less than" because there's a lone pair?

Connie Liang 3L

How come in the Lewis Structure for IO3- all the oxygens are single bond instead of double bonded? With double bonds, the Lewis Structure would still have a charge of -1 and have the same molecular shape.

Connie Liang 3L

All we need to know is that it's less than 109.5! :)

Connie Liang 3L

I loved Jane The Virgin! And you can never go wrong with Breaking Bad either... somewhat chemistry related too :)

Connie Liang 3L

I feel pretty okay! I haven't taken any chemistry since sophomore year Honors Chemistry, so I was nervous that I would not perform well in this class. However, at this point, I think I've learned study techniques geared for this specific class and I'm surprised at my performance so far. One thing I'...

Connie Liang 3L

I totally understand where you're coming from. What helps for me is focusing on comprehending the material instead of thinking about the letter grade or score percentage. I find that the more I think about grades, the more I get in my head about the exam! Good luck to everyone in their studies :)

Connie Liang 3L

For the final, I started studying a bit earlier than I normally would because I still need to make space for reviewing past units — of which some material has already gotten dusty. The textbook problems are honestly super useful, as well!

Connie Liang 3L

I'm reviewing every textbook problem, and putting an emphasis on questions before this unit to refresh my memory! I'll also review the notes I wrote down about why I got each problem wrong and how I can avoid making similar mistakes on like problems in the future.

Connie Liang 3L

I'm feeling good! Looking forward to finishing off this quarter strong and spending quality time with the fam this holiday season!!!

Connie Liang 3L

Is there a way to identify which ligands are monodentate? For example, I know that monodentate ligands contribute one lone pair of electrons to the transition metal. However, are there cases in which there are two lone pairs available in a certain ligand that's considered monodentate but only one of...

Connie Liang 3L

What's the difference between a complex ion and a coordination compound? Are they 2 names for the same thing?

Connie Liang 3L

It has to do with the chemical formula and composition. In this example, the H connects to the O for some reason, maybe it was already in a molecule with it and two molecules joined or because it is forming a Hydrogen bond, but it does not always have to bond with the central atom. Do you think it ...

Connie Liang 3L

For molecules that are presented how it is in part C that have many different parts, I like to do it in order to make sure that the correct things are bonded to each other. I believe the NH2 has to go on an end because it is in parentheses, but I could be mistaken. @Hailey, as a general rule, do mo...

Connie Liang 3L

How come you can't include nitrogen as the central atom in between the 2 carbon atoms? Is it because carbon is less electronegative and therefore at least one should be in the middle? Alternatively, how do you tell when you're able to draw the central atoms in the order that they're presented?

Connie Liang 3L

To draw the Lewis Structure with the lowest charge on each atom (so basically the most stable structure) an LA mentioned a tip: when the molecule has a net charge that is negative, you give the most electronegative element the charge. So for NCO- you would assign the O the -1 formal charge. And tha...

Connie Liang 3L

Are there any ways to make sure you're always drawing the lowest formal charge? For example, after drawing a Lewis Structure are we supposed to calculate using the formal charge formula the charge of each atom, or are there general tips to know to make sure you're always drawing structures with lowe...

Connie Liang 3L

If asked to draw a Lewis Structure on the midterm, will we be expected to draw the structure with the lowest total formal charge?

Connie Liang 3L

Definitely don't underestimate walks! I love taking breaks by popping on music and walking a quick lap around my neighborhood. You can soothe your eyes by seeing green and also just getting up and moving feels good after sitting down for so long. As for staying motivated, focusing on learning for th...

Connie Liang 3L

In lectures, Dr. Lavelle mentions that elements in the p-block especially want to form an octate. I understand this is because the s orbitals allow for two electrons and the p-block allows for 6 electrons for a total of 8. However, do elements in the d-block want to form octates as well or is it onl...

Connie Liang 3L

Can hydrogen ever have more than two electrons in a lewis structure? If no, how come?

Connie Liang 3L

Do atoms with a similar number of electrons have similar properties in terms of what element they are? Or are the number of electrons in different elements completely unrelated to one another?

Connie Liang 3L

I would recommend writing out each step to the conversion while you're doing it. Sometimes, I find myself doing the steps in my head and skipping writing them down which leads to confusion. Hope that helps!

Connie Liang 3L

Here's an example that might help! In the n = 1 shell, the subshell would be 1s. In the n = 2 shell, the subshells would be 2s and 2p. In n = 3 shell, the subshells are 3s, 3p, and 3d. And on and on. The subshells are s, p, d, and f and each one can hold a specific amount of electrons.

Connie Liang 3L

It's because of the Aufbau Principle which states that electrons will always fill up oribtals with lower energy first. The 4s orbital is slightly closer to the nucleus than the 3d orbital and therefore is considered a lower energy orbital.That's why electrons fill up the 4s orbital before the 3d one.

Connie Liang 3L

You can multiply by mv on both sides to get lambda x mv = h. Then divide both sides by lambda(m) to get v = h/lambda(m)

Connie Liang 3L

Thank you so much! I didn't examine the figure, so it was super helpful that you pointed that out!

Connie Liang 3L

Hi! I'm basing the definition of n1 and n2 from the constants and equations sheet we need printed out for the midterm. n1 would be considered the final energy level and n2 would be considered initial energy level. Now I'm kind of confused. I thought N1 is initial and N2 is final because if you deri...

Connie Liang 3L

Hi Natalie! I had some trouble with this one too. You want to know the wavelength of light that will be JUST enough to remove electrons from the metal with a work function of 3.21 x 10^-19 J. This means 3.21 x 10^-19 J is exactly equal to the energy of one photon because one photon is equal to JUST ...

Connie Liang 3L

Hi! I'm basing the definition of n1 and n2 from the constants and equations sheet we need printed out for the midterm. n1 would be considered the final energy level and n2 would be considered initial energy level.

Connie Liang 3L

Does anyone happen to know why we use kg as the convention for mass in the DeBroglie Equation rather than grams?

Connie Liang 3L

Part of the question reads "A 1.27-g sample of metallic copper was placed in a 26.32-g crucible and heated until all the copper had reacted with the oxygen in air to form an oxide." I was wondering if oxygen in the air is the same thing as oxygen gas. So would "oxygen in air" be ...

Connie Liang 3L

@Kaylee

Thanks for the reply! But if the number of moles stays the same then how is it possible to cut the number of molecules in half? Isn't the number of molecules dependent on the number of moles?

Connie Liang 3L

I'm confused by this quote from the solutions manual. "In order to find the number of times the volume must be doubled to get to one molecule, we can solve for the number of times this amount of molecules must be cut in half until it equals 1." I understand the basic concept that when you ...

Connie Liang 3L

I bought it but it still hasn't shipped to me and I haven't received any info on the shipping. Will our free trial be extended if it doesn't come in time before that? I'm not too sure if our free trial will be extended. But just in case, make sure to download the e-book which can be done through Sa...

Connie Liang 3L

I'm a bit confused on how electrons jump from energy level to level when excited. Can a photon excite an electron from ground state all the way to, for example, its third energy level? Or does it have to go one by one, so from the first energy level to the second and then to the third?

Connie Liang 3L

I was a bit confused about this too, but I believe there's no gas inside. Professor Lavelle mentioned just a traditional visible bulb.

Connie Liang 3L

It might be helpful to remember the definitions of both series. The Lyman Series is composed of emissions of when a hydrogen electron falls to the first energy level. This corresponds to UV light. The Balmer series is composed of emissions when electrons fall to the second energy level, and this cor...

Connie Liang 3L

In lecture, we learned that electromagnetic radiation, specifically waves of electric fields, can interact with electrons when passing through an atom, and excite them. I was wondering what about the magnetic field waves? Do they have any effect on electrons and what are these effects?

Connie Liang 3L

@Caelin, I believe the only reason the textbook converted the final answer to km was because the answer is a very large length. It should be fine if you keep it in m as long as it's converted correctly/the correct number.

Connie Liang 3L

Yes, that should be how you approach it based on the textbook question. I suppose the textbook could also ask for the number of atoms of element in a certain covalently-bonded molecule (which is why the questions says "or atoms, if indicated"). And in that case, it would be appropriate to ...

Connie Liang 3L

I don't believe so. Even though reactants can become a different state of matter following a chemical reaction, there should still be the same amount of that reactant due to the Law of Conservation of Mass. Therefore, when balancing equations, there should be the same amount of material on both side...

Connie Liang 3L

M = n/v is correct, but you can manipulate it to make finding the volume of the solution easier. So, you can multiply both sides by v and then divide both sides by M for v = n/M. You can then use the molar mass of CuNO3 to find the number of moles in 3.88 grams of CuNO3 which is .0309 moles. Now, yo...

Connie Liang 3L

I don't believe these will be provided just for general assignments like Sapling homework. However, it is a good thing to be familiar with SI units and their prefixes! Some prefixes are more pertinent than others in chemistry. For example, prefixes such as centi, milli, micro, and nano are more like...

Connie Liang 3L

Do all chemical reactions have to have a limiting reactant? Or is that not the case for every reaction?

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