CHEMISTRY COMMUNITY

Isabel Nakoud 4D

When will final grades be posted/available on MyUCLA?

Good Luck with the rest of Finals!

Isabel Nakoud 4D

I understand that Strong Acids have Weak Conjugate Bases and that Strong Bases have Weak Conjugate Acids... Does this mean that Weak Acids have Strong Conjugate Acids? Why or Why not? Can someone please thoroughly explain this to me. I am having a difficult time with weak acid and weak base reactions.

Isabel Nakoud 4D

Why does H have a greater electron withdrawing ability?

Isabel Nakoud 4D

Why is Structure 2 a stronger acid than Structure 4?

Isabel Nakoud 4D

Di you think naming will be emphasized much on the final as we just learned it in the last few days? Dr. Lavelle said that the Final will cover everything in the Syllabus as it is meant to and I think he implied that each section will be equally represented. So, yes. It will be emphasized as it is ...

Isabel Nakoud 4D

The homework asks, "12.127... The two strands of the nucleic acid DNA are held together by hydrogen bonding between four organic bases. The structure of one of these bases, thymine, is shown below. (a) How many protons can this base accept? (b) Draw the structure of each conjugate acid that can...

Isabel Nakoud 4D

Can someone confirm that the only bonds that Lewis bases make are coordinate covalent bonds?

Isabel Nakoud 4D

In the compound name,

sodium bisoxalato(diaqua)ferrate(III)

is there a significance to the parentheses around "diaqua" ? what is the purpose ? Does this change the writing of the compound somehow?

Isabel Nakoud 4D

What would the naming for this coordination compound be?

[Co(P(CH3)3)4]2(SO4)3

Isabel Nakoud 4D

On Dr. Lavelle's worksheet it is provided that SO4 2- written as OSO3 2- is "sulfato". What is it called when the ligand is bonded to the Sulfur atom? (Or, alternatively, is the sulfate ligand always attached to the Metal through Oxygen?)

Isabel Nakoud 4D

How are we supposed to know when to put the original ligand (i.e. CN- cyano ) vs. the iso-ligand (i.e. NC- isocyano) ?

Will the bonding atom always be underlined (on the final) in these cases?

Isabel Nakoud 4D

There are some ligands on Dr. Lavelle's worksheet, such as isothiocyanato, that we have not really seen in class or on the homework. Are we still expected to know/memorize them for the final?

Isabel Nakoud 4D

When a question is referring to "Group 5 transition metals" is it referring to the column with Vanadium or Manganese?

Isabel Nakoud 4D

Well, yes, but a double bond between Oxygen and Chlorine would also make the formal charge on Oxygen = 0.

Therefore, how do I know where to attach the Hydrogen if both Lewis Structures have a net charge of 0?

Isabel Nakoud 4D

Why does KBr have a neutral pH but KF has a pH greater than 7?

(This question is referring to Homework Problem 12.65 (c) and (d) )

Isabel Nakoud 4D

In problem 12.65 part (c),

When writing the aqueous solution of KF, how do we know to write the formula

F- + H2O --> HF + -OH

instead of making the solution about the K+ ion?

Isabel Nakoud 4D

Questions on the homework expected us to know the formula for acids such as Formic Acid... are we supposed to know names of acids like these by memorization for the final, or will the chemical formula be provided for acids? (esp. those such as Formic Acid that are not obvious)

Isabel Nakoud 4D

In 12.51,

HClO2 is a stronger acid than HBrO2 and same goes for H2CO3 > H2GeO3 on the claim that Cl and C are more electronegative than Br and Ge.

How does electronegativity affect the strength of an acid? Shouldn't HBrO2 and H2GeO3 be stronger acids because Br and Ge are larger?

Isabel Nakoud 4D

When do we know when to attach the H atom to Oxygen atom(s) instead of the central atom?

For example, as in HClO2

Isabel Nakoud 4D

Furthermore, can you calculate pKb with only this information (from the problem) provided?

Isabel Nakoud 4D

For problem 12.49 (provided in the image below). The solutions manual compares the pK b for the two molecules in order to compare the strength of their basic character. Are we supposed to be able to calculate these values, or are they given somewhere? Is there a way to compare the strength of their ...

Isabel Nakoud 4D

Can someone walk me through Homework Problem 12.27?

I understand that the desired pH is just -log (given M) = 1.6

However I don't understand part (b). Can someone please walk me through it?

Isabel Nakoud 4D

The 6th edition textbook claims that Bi2O3 is an amphoteric compound, yet Dr. Lavelle's slides from Friday's lecture claim that Bi2O3 is acidic. Which is correct?

Furthermore, in cases such as this, is there a way to identify amphoteric compounds other than simply memorizing them?

Isabel Nakoud 4D

In the reaction,

Cl- + SO2 --> SO2Cl

Both Cl- and the S in SO2 have lone pairs. Why is Cl- the Lewis acid and not SO2?

Isabel Nakoud 4D

Lone pairs on outer atoms (bonded atoms) don't make the molecule a Lewis base, correct?

For example, BF3 is a Lewis acid because Boron doesn't have any Lone Pairs.... the lone pairs on the bonded F atoms don't change that?

Isabel Nakoud 4D

I know that this was brought up on another post on Chemistry Community, but no one explained why there is no proton transfer.

Isabel Nakoud 4D

Homework 12.9 says that the formula

CH3COOH + NH3 --> CH3CONH2 + H2o

does not have Bronsted acids and bases because there is no proton transfer.

can someone explain how this is so ?

Isabel Nakoud 4D

Homework problem 12. 9 state that in the formula

NH₄I --> NH₃ + HI

NH₄⁺ is the Bronsted acid and that I^- is the Bronsted base. How is this possible, that the acid and base is the same compound?

Can someone please explain/walk me through this problem?

Isabel Nakoud 4D

What are the conjugate acids and bases in this formula?

NH₄ + H₂O --> NH₃ + H₃O⁺ + I^-

Isabel Nakoud 4D

Are the terms "Lewis base" and "Ligand" synonymous and interchangeable?

Isabel Nakoud 4D

Does the classification of Bronsted Acids and Bases go beyond the idea that acids are proton donors and bases are proton acceptors?

Are the Lewis and Bronsted definitions of Acids and Bases direct opposites of each other? (i.e. Lewis acids accept protons but Bronsted acids donate protons)

Isabel Nakoud 4D

Regarding the final exam...

Would I lose points for writing the conjugate base of HCOOH as COOH- instead of HCO2- ?

Isabel Nakoud 4D

Additionally, for oxalate, why is it only a bidentate and not a tetra dentate?

In addition to one oxygen from each side being bonded, can't the oxygen adjacent to it also be bonded, as demonstrated by Dr. Lavelle's example in class (the chemotherapy example with Cl) ?

Isabel Nakoud 4D

*Referring to question 17.33 (b) *

If the CO3^2- structure has 3 oxygen atoms, all equipped with at least one lone pair of electrons, then why can the ion only serve as a mono- or bidentate and not a tridentate ligand?

Isabel Nakoud 4D

When (CN) is a ligand, when are we supposed to use "cyano" vs. "cyanido" in our naming? I have seen both and am not sure how to distinguish between when to use either one.

Isabel Nakoud 4D

Why does LiCl exhibit greater ionic character than LiBr?

Isabel Nakoud 4D

Will we be asked questions about hybridization for molecules below the second period?

Isabel Nakoud 4D

In 4.95 of 6th edition, the molecule drawn and labeled hybridization shows that the lone pairs on Oxygen are "sp2" . Why is it sp2 and not 2 sp2?

Isabel Nakoud 4D

To clarify, I think I am trying to understand "unhybridized 2p orbitals" ?

Isabel Nakoud 4D

Can someone please explain through the concept of having "empty p orbitals" or something to do with lone pairs? Im referring to when the bond is ( C 2p, C 2p) I know Dr. Lavelle explained it in class but I don't actually understand what is occurring during this process of hybridization.

Isabel Nakoud 4D

<90 and <120 or <90 and 120?

Isabel Nakoud 4D

What are the bond angles on a Seesaw shape?

Isabel Nakoud 4D

When comparing the bond lengths of SO2 and SO3.. Both structures are made up entirely of double bonds... however, SO2 has lone pairs on the Sulfur and SO3 does not, so would it be correct to assume that SO2 had slightly longer bonds than SO3? (I am assuming that the bonds in SO2 would be longer beca...

Isabel Nakoud 4D

Can an organic compound have an ionic bond?

Isabel Nakoud 4D

Dr. Lavelle's slides read, "INCREASING SIZE OR MOLAR MASS RESULTS IN STRONGER ATTRACTIVE INTERACTIONS" can someone please explain why this is true and provide an example?

Isabel Nakoud 4D

In the formula for intermolecular potential energy, E , what does r stand for? Does it describe the distance between the two molecules, or the radius of one of the molecules? This is important because I am trying to understand the parameters that contribute to IM energy and I am trying to derive the...

Isabel Nakoud 4D

Can someone please provide examples of intermolecular forces (other than hydrogen bonding) in organic and biological molecules?

If possible, could you provide an example per type of intermolecular force (ion-ion, dipole-dipole, London...etc.)

Isabel Nakoud 4D

Why is hydrogen bonding so strong? What is unique about the force that attributes to its strength?

Isabel Nakoud 4D

The study guide reads, "Know the relative magnitudes of intermolecular forces and hydrogen bonds." What is this describing? What is the extent of knowledge that this study guide point is demanding (i.e. how much are we expected to know in detail?) Is this just asking that we can rank the i...

Isabel Nakoud 4D

Is describing the intermolecular force of ion-ion the same as describing molecules that share an ionic bond?

Isabel Nakoud 4D

The study guide reads, "Explain how covalent bond dissociation energy is related to covalent bond multiplicity, atomic radius, and the presence of unpaired electrons." First, what is covalent bond multiplicity? Second, can someone please provide the explanation for this? (i.e. answer this ...

Isabel Nakoud 4D

Therefore... it is safe to assume that when the electron density shape is Tetrahedral, the 2 lone pairs will always be next to each other? Thus, in CH2 2- , which has a tetrahedral, I would place the 2 LP next to each other.

Isabel Nakoud 4D

In the problem, for (b) the answer says the bond angle is "around 109.5"

Because the Oxygen has two single bonds, don't we assume that the Oxygen has 2 Lone pairs on it, and therefore the bond angle becomes < 109.5 ?

Isabel Nakoud 4D

Homework Problem 4.91 asks us to evaluate why Benzyne would be highly reactive based off what we know about its hybridization in its structure. What is the relationship between hybridization and reactivity? Can someone walk me through the process of using knowing about Hybridization to predict react...

Isabel Nakoud 4D

The lewis structure of Borazine has Boron atoms with double bonds connected to Nitrogen atoms in a hexagonal structure. How is it possible that the Boron atoms have a double bond?

Isabel Nakoud 4D

When you have 2 lone pairs, how do you know if you should place them next to each other (as with H2O) or if they should be opposite each other (as with XeF4)? I'm asking because the question of CH2 2- came up, and the structure isn't clear because I don't know where the 2 lone pairs should be placed...

Isabel Nakoud 4D

Can I assume that "angular" shape is the same as saying "bent" shape?

Isabel Nakoud 4D

For the 6th edition textbook Homework Problem 4.19 (b) why do we write the bond angles (tetrahedral shape) around the Carbon atoms in addition to the shape around the central atom? Should we always do this when writing shapes of organic molecules?

Isabel Nakoud 4D

Why does the Bent shape have bond angles less than 120 degrees rather than less than 180 degrees?

Isabel Nakoud 4D

Why is Nitrogen the central atom in N₂O?

Isabel Nakoud 4D

How have you guys been approaching the Homework Problems on Intermolecular forces? Should we always draw out the lewis structure and/or geometric shape of molecules before determining the possible/expected intermolecular forces? (otherwise, how will we predict the unique cases where the dipoles canc...

Isabel Nakoud 4D

If a question provides a molecule and then asks about the expected or potential intermolecular forces of the molecule, should we draw the lewis structure and/or geometric structure? I know that some molecules have a geometric shape that cancels out the dipoles, which changes the type of intermolecul...

Isabel Nakoud 4D

This problem comes from Homework 6.1 (c) on the 6th edition textbook.

For the molecule H₂SeO₄ , why can Hydrogen Bonding exist as an intermolecular force? Shouldn't the forces only be London or Dipole-Dipole?

Isabel Nakoud 4D

Stronger interactions imply that the bond is harder to break. Boiling points refer to the minimal temperature required to break the bonds of the substance. Therefore, stronger interactions cause the substance to have a higher boiling point, and vice versa.

Isabel Nakoud 4D

It doesn't hurt. You can demonstrate this through an arrow that points the direction the electrons are being pulled. On exams and homework problems, the instructions will likely specify when you should demonstrate polarity.

Isabel Nakoud 4D

As an example, think of enzymes. Substrate-Enzyme relationships depend on active sites shape. The shape of an active site depends on electron density. Without the right match of a substrate, enzymes cannot function.

Isabel Nakoud 4D

On the exam, what if the question asks for the lewis structure of a structure that has resonance, but one of the structure has lower energy than the other 2 resonance structures? For example, SO 2 Technically, there are three resonance structures for SO 2 However, one of the three structures (the st...

Isabel Nakoud 4D

Can someone confirm what the lewis structure of OCl2 is?

Is Chlorine the central atom (because it is less electronegative than oxygen)?

Can Chlorine form double bonds?

Isabel Nakoud 4D

Why is Oxygen more electronegative than Chlorine? (they are both adjacent to Fluorine so how would we be able to distinguish between them when looking at a periodic table)?

Isabel Nakoud 4D

Homework Problem 3.41 in the 6th Edition textbook:

Lewis Structure of Glycine H₂C(NH₂)COOH ?

Can someone please walk me through the process of creating this complex lewis structure in an efficient and/or strategic manner?

Isabel Nakoud 4D

The presence of exponents signifies that the atoms provided are not in their ground state but rather in ionic form. If we reflect on what Dr. Lavelle said in his lecture on Wednesday, ionic radius should increase as we go down a group. This is because each additional shell shields some electrons fr...

Isabel Nakoud 4D

Why are bonds strengthened by resonance?

Isabel Nakoud 4D

Will we be asked for electron configurations involving the f-orbials (Row 6 and below) on the Midterm on Monday?

Isabel Nakoud 4D

Many people have asked about #7 on Worksheet 2 and no one has responded.

Can someone please help us out and explain? The key is not clear... How did she get 1/n^2 = 0.0278 ???

Isabel Nakoud 4D

A bullet point on the Study Guide reads, "With respect to electron transitions that give rise to a UV or visible spectrum: understand the difference between electronic transitions in atomic orbitals (atomic spectroscopy) and electronic transitions in molecular orbitals (molecular spectroscopy)....

Isabel Nakoud 4D

I notice that in the textbook, when in solving equations, some solved equations are left with the constants written as their symbols and not as their numerical value. For example, see the photo I attached. Is this allowed for Test 2? Would we get full credit for an answer if we left the constants wr...

Isabel Nakoud 4D

Which equation do we use to figure this out?

Isabel Nakoud 4D

I am struggling to understand what the values of n1 and n2 are. Should n1 always be the smallest of the two numbers, or should n1 be the final position of the electron where n2 is the initial position of the electron? Additionally, if the electron were transitioning from (let's say) n=4 to n=2, then...

Isabel Nakoud 4D

It's important to remember that the periodic table was designed after the properties of elements were discovered and is deliberately organized in that fashion. I found this video that explains period trends (like the ones you're describing): https://www.youtube.com/watch?v=XK-WTYncldA

Isabel Nakoud 4D

It measures the uncertainty of the position or momentum of electrons

Isabel Nakoud 4D

Also, the solution to this problem says that the transition is from n = 1 to n = 3, but the problem says that energy was emitted during this process. Isn't energy only emitted when an electron transitions from a higher energy to a lower energy? So... if it transitioned from n =1 to n=3, it should ha...

Isabel Nakoud 4D

Nicolette_Canlian_3G wrote:why is the energy level of 102.6 nm 1?

This is what i don't understand. Even when I see pictures of the spectroscopy with the Lyman series, I notice that 102.6 is one of the values next to a line, but I'm not sure how to identify that it is n=1 .

Isabel Nakoud 4D

Hello, can someone thoroughly explain the answer to this homework problem {attached} ?

Isabel Nakoud 4D

This is all I know about the answer

Isabel Nakoud 4D

Jovian Cheung 1K wrote:

Does it start like this? (I'm curious too) :o)

Yes, it started like that!

Isabel Nakoud 4D

I cannot seem to get this question right for the life of me: "What is the wavelength of radiation emitted by a hydrogen atom in a transition from the n=6 to the n=5 energy level?" If you are able to help, could you actually write out all your numerical calculations (not just provide the th...

Isabel Nakoud 4D

In trying to solve the problem, "What is the wavelength emitted by a hydrogen atom in its transition from n=6 to n=5 energy level?" I tried to derive a formula from the formula E= ch/wavelength and E = -hR / n^2 I got the formula (wavelength) = -c (n^2) / R which I then used (Delta E) = Ef...

Isabel Nakoud 4D

While completing a practice test I noticed sometimes my answers were off by .001 and I am worried this will affect my scores on the exam. How accurate do we need to be on the test before we get points deducted? For example, if my answer was 3.21 x 10^27 and the answer key says it is 3.22 x 10^27 , w...

Isabel Nakoud 4D

Is test 2 solely going to be Quantum World material, or will it be cumulative? I'm trying not to fall behind in Chapter 1, but I also want to continue studying the review topics This is a good question if one of the TAs/UAs/Professor has an actual answer. Consider this for now though: Chemistry is ...

Isabel Nakoud 4D

What are the consequences of the electrons reacting with molecules in the air?

Isabel Nakoud 4D

Without having to go too in depth, can someone explain the reason for the idea of a"vacuum" and why this experiment has to take place under the conditions of one? I also noticed that a vacuum environment is a condition for the definition of the speed of light. Just looking for some backgro...

Isabel Nakoud 4D

This is one of the challenge problems of the homework for sure. After you finish part A, you know that O2 is the limiting reactant. Whenever we discover the limiting reactant, we use the mass value of that compound available and do some dimensional analysis to figure out how much product is produced...

Isabel Nakoud 4D

I spoke to my TA, and really they are only looking for you to know the fundamental compounds. For example, Water (H20), Carbon Dioxide (C02), and the diatomic gases (H2, F2, etc.) Remember that a periodic table should be given for the exam!

Isabel Nakoud 4D

A problem in the book asked, "How many formula units of the compound are present in 5.15 g of Magnesium Sulfate Heptahydrate?"

What are "formula units"?

Isabel Nakoud 4D

Please help I don't understand this problem! See attached IMG

Isabel Nakoud 4D

When you lose electrons, they always come from the highest energy level first because they are furthest away from the nucleus. We know that 4s orbitals have a lower energy than the 3d so therefore 4s electrons are actually lost first in ionization before 3d.

Isabel Nakoud 4D

5.00 g of KMnO4 is dissolved in a 150.00 mL flask of water. If 20.00 mL of this solution is removed and placed in a new 2nd 250.00 mL flask and filled with water, what is the concentration of the solution in the 2nd flask? Molar Masses: K (39.10 g/mol), Mn (54.94 g/mol), O (16.00 g/mol) Why do you u...

Isabel Nakoud 4D

I am stuck on the module post-assessment regarding whether two limiting reactants is possible. I would not think that two limiting reactants is possible unless the amounts of the two molecules perfectly completed the other. But then, no limiting reactant would exist. The options for why two limiting...

Isabel Nakoud 4D

It is universally applied through the definition of Avogadro's number, which is 6.02 x 10^23 particles. Scientists created the concept of the mole and defined it for their own purposes to convenience their calculations (so we just accept it for its definition and apply it as needed.) I have pondered...

Isabel Nakoud 4D

Can you clarify if its 2 points max. per week or 3 points max. ?

Thank you!

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