CHEMISTRY COMMUNITY

Cindy Nguyen 1L

Lily Emerson 1I wrote:you just need to do 14-(-log(1.1)) since you already know that the concentration of the new mixture is .55 - just multiply that by 2 moles of HO- to get the concentration

Where did you get 1.1 from?

Cindy Nguyen 1L

How does glycine act as a proton acceptor? I read that H can dissociate from O in a solution, so therefore that makes it able to be a proton acceptor, but what does this mean? How do you go about thinking if something can be a proton acceptor?

Cindy Nguyen 1L

How do you identify the composition of a bond? I know how to figure out if the bond is a pi or sigma bond, and I know what hybridization an atom would have. For example, sigma(C2sp 2 , C2sp 2 ). I know the sigma refers to a sigma bond, and the Cs refer to a bond between two carbon atoms. The sp 2 re...

Cindy Nguyen 1L

In a sicence lab, you created a stock soluiton of 1.50 M Na₂O.
How many milliliters of this stock solution would you need to make 210 mL of a .550 M Na₂O solution?

How do you go about solving this?

Cindy Nguyen 1L

This thread might help. https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=33&t=31624&p=103217&hilit=Lewis+structures&sid=450ab185a9474d380218e0e88a8cc6d7#p103217 "formal charge purpose" is the title of the thread. Basically you draw a Lewis structure and then calculate th...

Cindy Nguyen 1L

6 regions of electron density = 5 bonded atoms + 1 lone pair. ex. SF4. Tetrahedral has 4 regions of electron density.

Cindy Nguyen 1L

If it has the same amount, how does pH decrease? What effect does temperature have in this situation?

Cindy Nguyen 1L

Yes, a sigma bond is stronger than a pi bond. This is because the length of a sigma bond is shorter than a pi bond, and it takes more energy to break a sigma bond. Because a double bond is a sigma bond and a pi bond and every type of chemical bond has to have at least one sigma bond, how are double...

Cindy Nguyen 1L

Which parts of the textbook you should read, what topics pertaining to it,and problems you should be able to solve are all listed in the syllabus: Coordination Compounds and their Biological Importance (oxidation states, coordination number, shape and structures of coordination compounds; biological...

Cindy Nguyen 1L

I would like some clarification on the bond lengths in sp2 and sp3 orbitals. Are the bond lengths in sp2 orbitals shorter because the orbitals have more s-orbital character (33% as opposed to 25% in sp3) and more s-orbital character means the electrons are closer to the nucleus? Also, in regards to ...

Cindy Nguyen 1L

Just to confirm: BF3 would have an sp2 hybridization, but it has an empty p-orbital (can accept a lone pair and have an octet). When BF3 undergoes an acid-base reaction, Boron can accept a lone pair from a Lewis base, and that bond is called a coordinate covalent bond? And that coordinate covalent b...

Cindy Nguyen 1L

I agree. The atoms wouldn't need to have hybridized orbitals when it's not bonding. When the orbitals are hybridized, the electron(s) is/are moved to a higher energy orbital. For example, carbon alone is at a 2s 2 2p 2 . That is a lower energy state than if it had 1 unpaired electron in its s orbita...

Cindy Nguyen 1L

To add on, there are a few compounds that the central atom isn't the least electronegative because the formal charges are best that way.

Cindy Nguyen 1L

You also have to keep in mind that the actual structure of the compound is a hybrid of all the resonance structures. So one resonance structure wouldn't have a greater effect on the shape or anything. As stated above, since resonance structures is basically shifting double bonds around, the bonds ar...

Cindy Nguyen 1L

3.45 asks us to draw the resonance structures for ClNO2. I drew that N would have a double bond with an oxygen atom and a single bond with the other oxygen atom. With the oxygen with a single bond with Nitrogen, I drew chlorine bonded to it so that that oxygen would now have two bonds. This way the ...

Cindy Nguyen 1L

3.35 states "Write the Lewis structure of (a) tetrahydridoborate ion, BH4"; (b) hypobromite ion, BrO"; (c) amide ion, NH2" I don't understand how you can use covalent bonds for molecules like BH4- or NH2- if they're ions. I know ionic bonds, you gain or lose electrons, and for co...

Cindy Nguyen 1L

Kekule structures is in Chapter 3, but it's just a fancier version of a Lewis structure that shows its shape. We would be told if the molecule would have a cyclic/ring structure, and then we can form our Lewis structures based on that.

Cindy Nguyen 1L

The cations and anions have to be treated separately as they aren't linked by shared pairs (stated in the textbook). So what would they be linked by so that the ions are together? For example, ammonium bicarbonate, what links the three ions together so that they aren't just separate ions floating ar...

Cindy Nguyen 1L

In the textbook, it says, "As well as a bonding pair of electrons, a fluorine molecule also possesses lone pairs of electrons; that is, pairs of valence electrons that do not take part in bonding. The lone pairs on one F atom repel the lone pairs on the other F atom, and this repulsion is almos...

Cindy Nguyen 1L

Other than just memorizing it, practice makes you know it and then calculate them faster.

Cindy Nguyen 1L

Not the gas phase. Condensed phase = liquid or solid state.

Cindy Nguyen 1L

For the third row of the periodic table, we don't put any d-orbital electrons in their ground state configurations as they don't have any in the d orbital. However, since their energy level is 3 (n=3), they are able to have more electrons. They have a whole new shell rather than be just n=2, so the...

Cindy Nguyen 1L

No. Group 3 elements in general often have incomplete octets.

Cindy Nguyen 1L

This relates to "expanded octets." Chlorine is an element that can have an expanded octet. There are discussions on Chemistry Community about expanded octets.

Cindy Nguyen 1L

For the third row of the periodic table, we don't put any d-orbital electrons in their ground state configurations as they don't have any in the d orbital. However, since their energy level is 3 (n=3), they are able to have more electrons. They have a whole new shell rather than be just n=2, so ther...

Cindy Nguyen 1L

If you can draw more than one Lewis structure that is equivalent to each other, then it displays resonance. This usually occurs in molecules that have double bonds and single bonds. For example, benzyne has double bonds on every other bond between two carbons (and single bonds for the other carbons)...

Cindy Nguyen 1L

I don't think radicals are necessarily made from atoms giving up or gaining electrons. If they do that, they would make bonds. I think radicals are made because of combustion or if something breaks a bond. Some examples would be gas from a muffler or broken bonds because of UV rays.

Cindy Nguyen 1L

An extra detail is that the first four elements never have an octet.

Cindy Nguyen 1L

To add onto the other replies, increasing the intensity/brightness/amplitude of the photons would mean more electrons can be emitted (since there is a 1:1 ratio with one photon ejecting one electron). However, if the threshold energy isn't even reached per photon, an electron would not be emitted. T...

Cindy Nguyen 1L

I don't think you should necessarily memorize keywords in order to use different equations. Different problems have different contexts. In the example you gave for last Friday's midterm session, you had to use the work function + the kinetic energy to eventually find the wavelength because in the fi...

Cindy Nguyen 1L

You take away the electrons from the outer shell (the valence electrons). In this case, the electrons in the s and p orbitals are the outermost electrons.

Cindy Nguyen 1L

I'm confused on how the covalent radius can be different than atomic radius between two atoms. I thought a covalent radius would just be the atomic radius between two atoms that have a covalent bond. Same with an ionic radius but with two atoms with an ionic bond. Is the difference because the coval...

Cindy Nguyen 1L

Interacting waves produce diffraction patterns. Particles do not. When two waves interact, their amplitudes are combined. If two waves are in sync with each other, then the resulting amplitude is the sum of the two amplitude of the waves. If the two waves are not in sync (or in phase) with each othe...

Cindy Nguyen 1L

In my version of the test and if I'm thinking of the same problem, it did say the electrons were excited from a ground state to an excited state. It did not say which energy level it was excited to though. However, you do not need to know the energy level to solve this problem. It gave you a wavelen...

Cindy Nguyen 1L

To add on to the replies above,

A greater amplitude would mean more photons. If all these photons had a high enough frequency, then more electrons can be emitted.

Cindy Nguyen 1L

In my version of the test, it was said that the photons were absorbed . That's why lines appear. Because we know this, it would mean the photons had the correct amount of energy in order to be excited to another energy level. It was given on the test that it had enough energy. We did not have to ass...

Cindy Nguyen 1L

How do you find a mole?

Eenie meenie minie mole.

-an original

Cindy Nguyen 1L

On the front page of Test 1, the Rydberg Formula is $E_{n} = -hRhn^{2}$ . In lecture, it is $E_{n}=\frac{-hR}{n^{2}}$ . I was wondering how the formula on Test 1 is equivalent to the one given in lecture.

Cindy Nguyen 1L

The brighter the light is, the more intense it is. In regards to the amplitude, then there is a larger amplitude. Let's say I shine a flashlight at you: When the waves of light are in sync with each other, they create a constructive diffraction pattern. This means the waves overlap together, and the...

Cindy Nguyen 1L

If I understand correctly, the names of each series refers to the range that the electron moves from energy to energy level. So for example, when an electron transitions from n=2 to n=1, that is called the Lyman Series. The Balmer series represents the drop from higher energy levels to n=2. These di...

Cindy Nguyen 1L

I noticed how the textbook uses "s^-1" instead of "/s" (like Js^-1 instead of J/s). Also, ms^-1 is the same as m/s. However, I was wondering if there was any special reason that it's notated with specifically a negative exponent. Is the reason chemistry-related or is it just a pr...

Cindy Nguyen 1L

I would like clarification for something Dr. Lavelle explained during lecture. We were on the slide for calculating deltaE using the empirical equation for an H-atom (-hR/n^2) Dr. Lavelle explained that the reference point is when the electron is fully removed, and the ground states for elements sho...

Cindy Nguyen 1L

People always say all the good chemistry jokes Argon, but NO3-, they're not.

Cindy Nguyen 1L

If you're not part of the solution, you're part of the precipitate.

Cindy Nguyen 1L

What do you call an acid with an attitude?

A-mean-oh acid.

Cindy Nguyen 1L

What kind of dogs do chemists have?

Laboratory Retrievers

Cindy Nguyen 1L

Hello, I was going over the example problem in the textbook and was confused on Step 3 (b). The equation is CaC2(s) + 2 H2O(l) -> Ca(OH)2(aq) + C2H2(g). It's balanced. We are asked if either 100g of water or 100g of calcium carbide is the limiting reactant, what mass of ethyne is produced, and what ...

Cindy Nguyen 1L

I understand how the answer is so, but if the problem asked to find the empirical formula of the compound didemnin-A, how can the ratio for Carbon be 8.143 when the number of atoms should/is always a whole number?

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