CHEMISTRY COMMUNITY

Jason Nguyen_1B

When we are determining hybridization, we count the number of electron density regions which includes bonds as well as lone pairs. For example, NH3 has 3 single bonds and 1 lone pair. Since we count both the bonds and lone pairs, NH3 has 4 regions of electron density thus it is SP3 hybridized. And j...

Jason Nguyen_1B

[OH-] and pOH aren't the same thing but they're related. The difference between the two is that [OH-] represents the concentration of [OH-] or the molarity of OH-. It basically represents the concentration of OH- that is produced when a strong base reacts with water for example. pOH is a value that ...

Jason Nguyen_1B

Hi! For 6B.5, the question asks to find the pH and the pOH. For part A and part B, they give us the concentrations of strong acids. Thus in order to find the pH of those concentrations, we simply find the -log of those concentrations (because strong acids completely dissociate so the moles of a stro...

Jason Nguyen_1B

Hi! I understand that ligands can be polydentate if they are able to form two or more bonds to the transition metal cation and thus be a chelating ligand. However, for a ligand to be polydentate and chelating, does the ligand have to follow the lonepair-spacer-spacer-lonepair model? If so, are there...

Jason Nguyen_1B

For this question, the textbook stated that As2O3 is amphoteric. I know that metalloid oxides typically form amphoteric compounds. However on professor Lavelle's lecture on Friday (12/4), he showed a periodic with basic, acidic, and amphoteric oxides. On that periodic table, it showed As2O3 as an ac...

Jason Nguyen_1B

The reason why H2PO4- can act as an acid is because it can donate a proton. In this case, since H2PO4- has a hydrogen, it can donate a H+. H2PO4- can also act as a base because its oxygen has a negative charge. This will attract a H+ proton and allow it to accept a H+ proton.

Jason Nguyen_1B

I am told to arrange aqueous solutions from most acidic to most basic, however I'm stuck on how to find the pH level given the concentration of OH-. I am told that [OH-]=1x10^-9, but I'm unsure how to find the pH and rank it given this concentration. Could someone explain how I can determine the ran...

Jason Nguyen_1B

I think it has to do with the different naming convention for cyanide. The old name convention for cyanide is cyano but the new IUPAC name convention for cyanide is cyanido. Even though the names are different, they are both used to name the same ligand, cyanide.

Jason Nguyen_1B

Hi! I believe that ligands bonded to a central atom will always form a bond with the transition metal cation by donating its electron pair. Since the ligand forms a coordinate covalent bond with the transition metal, by definition of a coordinate covalent bond, the ligand will provide both of its el...

Jason Nguyen_1B

I understand that H2PO4- is the amphoteric substance that can act as a Bronsted acid and a Bronsted base. However, I don't understand when the explanation states that H2PO4- has both a conjugate acid and a conjugate base. Can someone explain what this means and if it relates to H2PO4- being amphoter...

Jason Nguyen_1B

For the XeF2 lewis structure, there are 5 regions of e- density on the Xe atom. As a result, Xe has an electron density geometry of trigonal bipyramidal. However, since Xe has 3 lone pairs, the most favorable position for the lone pairs to be located would be on the equatorial position of a trigonal...

Jason Nguyen_1B

Yes you are correct. Ligands form a coordinate covalent bond with a transition metal ion. The ligand would be a lewis base since it donates the e- pair and the metal ion would be an acid base since it accepts the e-. Because the ligand forms a coordinate covalent bond, it means that the ligand contr...

Jason Nguyen_1B

I've been doing questions about hybridization and I've been able to get them right but I still have a hard time understanding what hybridization is and how it relates to what we are learning. Could someone give me a brief rundown of hybridization and how it relates to bonding?

Jason Nguyen_1B

Hi! For question 17 there are 3 structures for C3H4 you have to draw. One of the structures has a C-C double bond. The other has a C-C triple bond. And the last has a C-C double bond but in a ring shape (the three carbons are formed in a triangle). For question 18, the C-C bonds for all 3 structures...

Jason Nguyen_1B

What is the distinction between a Pi Bond and a Pi Molecular Orbital?

Jason Nguyen_1B

For the final, you may have to memorize the bond angles of the basic molecular geometry, such as linear, trigonal planar, tetrahedral, trigonal bipyramidal, and octahedral geometry. However, for molecules with lone pairs, I think you just have to understand that the bond angles would be slightly les...

Jason Nguyen_1B

I was wondering why NO2- has a bent molecular geometry. I thought that molecules have a bent molecular geometry if there are 2 bonding pairs and 2 lone pairs on the central atom. Are there more instances when a molecule can also have a bent geometry?

Jason Nguyen_1B

I would also like to add that dashed lines indicate bonds facing away from us while bold bonds indicate atoms facing towards us from our point of view.

Jason Nguyen_1B

During the lecture, Dr. Lavelle stated that lone pairs in the equatorial plane are more favorable for molecules with a seesaw geometry such as SF4. I'm still a bit confused as to why a lone pair in the equatorial plane creates a more stable molecular geometry compared to a lone pair in the axial pla...

Jason Nguyen_1B

I have a general question about molecular shapes. Would CH3F have a tetrahedral molecular geometry even though there are 3 C-H bonds and 1 C-F bond? Also would the C-F bond have any effect, on bond angles for example?

Jason Nguyen_1B

The lewis structure where the formal charges of the atoms are close to zero result in lower energy/more stable structures, so these are the best structures based on formal charge. To determine which resonance structure is the best on formal charge, you want to choose the structure that has the least...

Jason Nguyen_1B

A hydrogen bond can only occur between a hydrogen and a nitrogen, oxygen, and fluorine atom. For a hydrogen to undergo hydrogen bonding, the hydrogen must first be covalently bonded to very electronegative atom (only N, O, and F). The second parameter is that the hydrogen must be close to another el...

Jason Nguyen_1B

Atoms in period 3 and below of the periodic table can have an expanded octet and thus accommodate more than 8 electrons because they d-subshells, allowing it to have more than 8 electrons in its valence shell. Periods 3 and below have an expanded octet because when the principle quantum number n=3, ...

Jason Nguyen_1B

Hi,

I am confused as to why the electron configuration for Pd is [Kr] 4d^10. I thought that its electron configuration should be [Kr] 4d^8 5s^2. For example, Ni, the element right above Pd, has an electron configuration of [Ar] 3d^8 4s^2, so I'm wondering why Pd doesn't follow the same pattern.

Jason Nguyen_1B

When answering a question on sapling, they stated that SO2 is a lewis acid. The answer they stated was that SO2 is a lewis acid because "molecules with polar double bonds also accept electrons." Can someone explain what this means and how it makes SO2 a lewis acid?

Jason Nguyen_1B

Hi! It's because P is in the 3rd row of the periodic table, so its possible subshells are the s, p, and d subshells. As a result, P can accommodate more than 8 valence electrons and since it's the central atom in this lewis structure, it can have more than 4 single bonds. For the second part of your...

Jason Nguyen_1B

Yes you are correct, the formal charge of each atom should add up to the total charge of the molecule. For example for SO4^-2, the formal charge of the S and 4 O should add up to -2.

Jason Nguyen_1B

Atoms in the 3rd period/row or higher of the periodic table can have more than 8 valence electrons. This is because these atoms have d-orbitals in their valence shells which can accommodate more than 8 electrons. Other exceptions to the octet rule include H, He, Li, and Be, which do not have octets.

Jason Nguyen_1B

It is because half full and full d subshells have lower energy, resulting in ground-state electron configuration. When writing the ground-state electron electron configuration for silver, you first end up with [Kr] 4d^9 5s^2. However, the d subshell has 9 electrons in its subshell, but I stated that...

Jason Nguyen_1B

Ionic and covalent bonds were discussed during the lectures, but I was wondering if anyone could explain to me the difference between ionic and covalent bonds? I also wanted to know if certain elements form ionic/covalent bonds?

Jason Nguyen_1B

I'm a bit confused as to why cations are smaller than their parent atoms while anions are larger than their parent atoms. Can someone help explain this to me?

Jason Nguyen_1B

I believe you apply Hund's Rule to this question. Hund's Rule states that due to electron repulsion, electrons in the same subshell occupy different orbitals with parallel spin, and this results in the lowest energy electron configuration which represents the ground state. For carbon, the two electr...

Jason Nguyen_1B

Ionization energy is the energy needed to remove an electron from an atom in the gas phase. As you move down the periodic table, the radius of the atom increases because you add electron shells as you move down. Because the electrons are further away from the nucleus, they are less attracted to the ...

Jason Nguyen_1B

What Jaden says makes sense because electron affinity can be defined as E(x)(g) - E(X-)(g) where you subtract the energy of a negative ion in the gas phase from the energy of a neutral atom in the gas phase. I also think that adding electrons can release energy because adding an electron increases t...

Jason Nguyen_1B

The reason why wavelength and frequency is not affected by the number of photons is because each photon has its own specific wavelength and frequency. If one photon has wavelength λ and frequency v, then in 100 photons, the wavelength and frequency will be the same since each photon has the same wav...

Jason Nguyen_1B

For this question, there isn't a specific equation to determine the number of spectral lines. Spectral lines are just the specific wavelengths that are emitted or absorbed when an electron makes a transition in energy. For this question, since the electron starts off at an energy level n=5, it can m...

Jason Nguyen_1B

Ok if the question just said that the uncertainty in position is a given radius, I would double the radius in that case right?

Jason Nguyen_1B

The hydrogen atom has a radius of approximately 0.05 nm. Assume that we know the position of an electron to an accuracy of 1 % of the hydrogen radius, calculate the uncertainty in the speed of the electron using the Heisenberg uncertainty principle. Usually when given the radius, we would double it ...

Jason Nguyen_1B

I believe the Rydberg Equation is just another way to find the emitted or absorbed light following a quantum level transition and it is derived from the empirical formula. You could use either the empirical formula or Rydberg's Equation but Professor Lavelle prefers that we use the empirical formula...

Jason Nguyen_1B

I was having trouble with the mass of N2 and plugging it into De Broglie's equation but I think I got it now. When we calculate the mass of a N2 molecule, we can first calculate its molar mass, which would be 28 g. mol^-1. We now know the mass of N2 per mole, but we want the mass of a single N2 mole...

Jason Nguyen_1B

I heard that's what professor Lavelle said as well thank you!

Jason Nguyen_1B

Also, I believe that once electrons are ejected, they can interact and collide with air molecules, causing the electrons to lose energy. Thus, when the electrons do reach the electron detector, they will have lower energies then they should resulting in inaccurate data.

Jason Nguyen_1B

Question: A red line is observed at 656.3 nm in the spectrum of atomic hydrogen. Determine the values of n for the beginning and ending energy levels of the electron during the emission of energy that leads to this spectral line. (What is n2 and n1) I am unsure of how to begin to solve this question...

Jason Nguyen_1B

Hi! For this question since they give you either the frequency, wavelength, or energy for each event, you can use the formulas E = hv and c = λv to complete the table. For example in the first line, they give the frequency, so you would use c= λv to find the wavelength and E = hv to find the energy ...

Jason Nguyen_1B

Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1. What is the kinetic energy of the ejected electron? For this question I'm a bit confused. I know that I have to use the equation 1/2mv^2 to calculate the ki...

Jason Nguyen_1B

I also got a slightly different decimal for my answer than the answer in the book. Solving the question, I got 8.8418 x 10^-12 m or 8.8418 pm. Maybe the book used rounded numbers to solve the question. Even though the decimals are slightly different, both answers are correct.

Jason Nguyen_1B

Part A of F3 asks to write the formula for nitric acid. How would I know what the formula of nitric acid looks like if I wasn't familiar with the compound? Would I just have to search up nitric acid and get the formula from there?

Jason Nguyen_1B

Oh jeez, I didn't know the diagram could be read like that to figure out the number of each atom. I understood your explanation pretty well but hopefully they give me the molar mass because the entire procedure seems a bit complex to me right now.

Jason Nguyen_1B

For this question, do we need to know the chemical formula 2-butanone and 3-methyl-3-hexanol in order to solve this question? And if we did, would we just search up what the chemical formula is if we didn't know beforehand?

Jason Nguyen_1B

What does the chemical equation look like for this question? Is knowing the chemical equation necessary for solving this question?

Jason Nguyen_1B

I use Google Chrome and If you're still having problems with allowing pop-ups on Google Chrome, what you can do is manually add websites that you want to allow pop-ups. What I did was that I accessed Google Chrome's settings and searched up "pop-ups" in the search engine. From there, I wen...

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