CHEMISTRY COMMUNITY

Mahnoor_Wani_1I

I believe that all the UAs workshops are helpful. They all have a good understanding of the materials and always try their best to help the students. Personally, I liked going to Justin's and Kate's workshop because they do a really good job on teaching the material and answering any questions stude...

Mahnoor_Wani_1I

From chem 14a I learned not to stress over chemistry too much. My advice would be to attend one or two UA sessions per week, do textbook problems, review lecture notes, and make a study guide using the learning outcomes

Mahnoor_Wani_1I

The coefficient on HD is 2 so there are two moles on the reactant side. The coefficient on H2 gas and D2 gas is 1 so there are 2 moles of gases on the product side. I think you are probably miscalculating the number of the moles on each side. I don't see 3 moles of reactants for d. Isn't the H2 on ...

Mahnoor_Wani_1I

The coefficient on HD is 2 so there are two moles on the reactant side. The coefficient on H2 gas and D2 gas is 1 so there are 2 moles of gases on the product side.
I think you are probably miscalculating the number of the moles on each side. I don't see 3 moles of reactants for d.

Mahnoor_Wani_1I

If you want to practice ICE tables with two positive x values, topic 5I has textbook problems that pertains to these types of problems. Usually, one of the positive value, when plugged in, would cause you to have a negative new equilibrium concentration.Therefore, you will be able to eliminate that ...

Mahnoor_Wani_1I

I would say use 10^-3 because this is the value used in the textbook too. The video are few years old and the chemistry community is constantly evolving with new ways to write/identify things. So, I would trust his lecture more since they are newer than the audio visual videos.

Mahnoor_Wani_1I

I understand how to use the ice/rice table to calculate the value of x to find the concentrations. Hypothetically, what if both the values of x we get from the quadratic formula are positive, then which one would we use to calculate concentrations?

Mahnoor_Wani_1I

ATM is the standard unit of measure of pressure so we are most likely dealing with atm in chemistry, but I also agree with Sarah it depends on the units given in the problems.

Mahnoor_Wani_1I

Prioritize mental health over everything and be more productive

Mahnoor_Wani_1I

It is not mentioned in the syllabus so most likely not.

Mahnoor_Wani_1I

Last quarter what helped me the most with applying the concepts we learned in class was to go UAs workshops/step up session (one a week) and do practice problems in the textbook.

Mahnoor_Wani_1I

I know that the equilibrium constant is affected by the temperature, but why is it affected by temperature? Why is it only depended on temperature and not the the concentration of reactant we start off with.

Mahnoor_Wani_1I

spending more time with my family and focusing on finishing my shows

Mahnoor_Wani_1I

https://quizlet.com/462765872/ligand-na ... ds/?x=1jqt
here is another quizlet that someone in chem14a made that you can use!!!

Mahnoor_Wani_1I

we are expected to just write the basic formula for a compound he gives us but are not expected to calculate it

Mahnoor_Wani_1I

Thank you!!! This is really helpful

Mahnoor_Wani_1I

You can rewatch lectures that pertain to the topic that you are struggling at, you can also watch YouTube videos online that explains the topic, do practice problem and compare your answers with solution manual and see what you did wrong

Mahnoor_Wani_1I

Mari Williams 2k wrote:Going over them once or twice on quizlet is always helpful!

I agree with this! memorization is key to understanding common conjugates. There is also many quizlet available online so you do not have to worry about making one

Mahnoor_Wani_1I

Draw the lewis strcuture of the molecule
The ligand must have at least 2 atoms with lone pairs

Mahnoor_Wani_1I

Electron geometry describes the arrangement of electron in a compound. Molecular geometry describes the arrangement of atoms, excluding lone pairs

Mahnoor_Wani_1I

Coordination number is number of bonds (number of ligands) attached to the Transitional Metal. In the square planar complex, there are only 4 ligands attached and 2 lone pairs. So the coordination number is 4. REMEMBER NOT TO CONFUSED COORDINATION NUMBER WITH ELECTRON PAIRS OF TM!

Mahnoor_Wani_1I

[Co(NH3)4Cl2]Cl In naming coordination compounds, ligands are named in alphabetical order first and then the TM with their oxidation number. From the compound above we can see that Cl2 and NH3 are the ligands. Since there are two cl anions it is dichloro and since there are 4 NH3 it is tetraammine. ...

Mahnoor_Wani_1I

I don't think there any past final exams made available. However, in many of the workshops the questions are pulled directly from midterms and finals exams so you should be prepared by attending workshops. Also, you should do textbook problems to study. I think textbook problems are most similar to ...

Mahnoor_Wani_1I

Coordination numbers are the numbers of bonds ligands forms with the transitional metal. Basically, they are the number of ligands bonded to TM. If you are still confused I think you should rewatch the Monday lecture (specifically the coordination compound part), Dr. Lavelle goes into dept about coo...

Mahnoor_Wani_1I

When you draw out the lewis structure of CO3 2- you can see that there are two lewis structures. One structure has one CO double bond and two single CO bond. In this structure the Oxygen is capable of interacting with a transitional metal at two different places so it is classified as bidentate. The...

Mahnoor_Wani_1I

Yes, you are correct. +3 is the oxidation state of the Co. NH3 is neutral and since the charge of two chlorine outside is -2 the compound charge must be +2. Therefore, since Cl inside has a charge of -1 you set this equation: X -1 = +2. The X aka the oxidation of Co is +3

Mahnoor_Wani_1I

There is a lot of pre-made quizlets available that you can use as flashcard to study or as a practice test. I recommend this method because you can use quizlet on any browser anywhere

Mahnoor_Wani_1I

I'm not really sure if we can find most favorable structure if there is no resonance. They all have equal net charges of 0 too so I think they are all favorable.

Mahnoor_Wani_1I

They are really helpful! I try to go to at least two workshops per week. I think the workshops problems are very similar to the structure. And they go step-by-step to make sure you understand the concept/problems

Mahnoor_Wani_1I

Lone pairs have a stronger repelling effect than electrons in bonds. This is because lone pair have a larger electron cloud whereas bonding pair are being held in place by the two atom. Thus, to have the lowest energy/stable shape we need to have lone pairs as far away from other electron density re...

Mahnoor_Wani_1I

Is there a possibility that the finals are going to be curved?

Mahnoor_Wani_1I

Pi bonds are bonds formed by overlapping two parallel unhybridized p orbitals. If there are more than one adjacent orbitals the central atom can overlap with then its called a delocalized pi bonds. You can easily identify a delocalized pi bond if there is more than one adjacent atom from which a dou...

Mahnoor_Wani_1I

Here are my tips: ATTEND UAs Sessions!! They go over previous years midterm/final questions so you get used Dr. Lavelle exam structure. Make a study guide using the unit outlines, lecture notes, and textbook I think textbook problems + UAs session problems are the most similar to the exam so priorit...

Mahnoor_Wani_1I

From what I heard Chem 14B material is harder. The textbook is same. Based on the syllabi for 14B there are Two 50 minute tests, One 2 hour midterm exam.
One 3 hour final exam.

Mahnoor_Wani_1I

I always have test anxiety right before any test. The best thing to do in my opinion is finding a study routine that works best for you (aka not procasinate and divide things up for study) and clearing your mind by doing what you like the most (watching movies, talking a walk, or sleeping)

Mahnoor_Wani_1I

What is the difference between unhybridized and hybridized orbitals? How do we determine how many unhybridized orbitals a molecule have?

Mahnoor_Wani_1I

Lone pairs have a stronger repelling effect than electrons in bonds. This is because lone pair have a larger electron cloud whereas bonding pair are being held in place by the two atom. Thus, to have the lowest energy/stable shape we need to have lone pairs as far away from other electron density re...

Mahnoor_Wani_1I

I don't think so since it was only briefly mentioned in the textbook. Calculating it is a really complicated procedure that is beyond the scope of chemistry 14A so you don't have to worry about it Also, in order to analyze it we just look at the different colors. Since each color represent either th...

Mahnoor_Wani_1I

Based on the textbook and lectures, we should know that homonuclear diatomic molecules, benzene, methane, ethylene, and most organic molecules are non polars.

Mahnoor_Wani_1I

http://www.chem.ucla.edu/~harding/IGOC/ ... oment.html
I was also struggling with understanding what dipole moments are and the website above helped me understand them better. I hope It can help!

Mahnoor_Wani_1I

When I was looking up examples of sigma and pi bonds on google for a reference, I saw that there exist something called a delta bond. What exactly is a delta bond and how do we determine if a covalent compound has a delta bond? Also, are we expected to memorize delta bond for this course?

Mahnoor_Wani_1I

If you are struggling with memorizing the molecular shapes, watch this video: https://www.youtube.com/watch?v=r2XmaiEC0Vw!

Mahnoor_Wani_1I

Review your lecture notes, attends workshops/step sessions, practice problems from the book + homework, and if you are unsure about a topic don't be afraid to ask in the chemistry community !

Mahnoor_Wani_1I

Your TA will tell you when to start after making sure your desk is clear. After you are done, I am pretty sure you can just leave the zoom.

Mahnoor_Wani_1I

Basing of the problems in book about radicals, we should know that radicals have unpaired spins, be able to draw radicals/determine which structure is a radical, know that radicals are highly reactive/ can't be stored

Mahnoor_Wani_1I

Least formal charges = more favorable. More electronegative atom should have the negative charge since it attracts electrons. If mot electronegative atom doesn't have the negative charge then its not favorable

Mahnoor_Wani_1I

I have the same question about part c. How do we determine which atom bonds with which when we have three different atoms ?

Mahnoor_Wani_1I

How does resonance lowers energy and make molecules stable?

Mahnoor_Wani_1I

I'm also enrolling in 14B In second enrollment because there is usually enough seats because it is in such a high demands

Mahnoor_Wani_1I

one of the LA mentioned that oxidation states will not be tested. I think we just need to have a general understanding of them

Mahnoor_Wani_1I

What is the difference between temporary and permanent dipole moments? How are they both formed?

Mahnoor_Wani_1I

I think it is both. They can occur between two ions in an ionic bond or between atoms in a covalent bond

Mahnoor_Wani_1I

"E stands for three things: Electronegativity, Electron affinity, and ionization Energy. All of these E’s increase going up and to the right of the periodic table." from MCAT mnemonics Periodic Trends

Mahnoor_Wani_1I

Why is the electron affinity for Carbon greater than nitrogen? Doesn't carbon occupying an orbital outside a closed shell means it farther from nucleus and requires energy.
Also, is the Nobel gas and C&N are the only exceptions in electron affinity?

Mahnoor_Wani_1I

Just out of curiosity, If it is more than 5 orbitals, do we go by alphabet order or is there a specific order you need to go by

Mahnoor_Wani_1I

Would the TA office hours and UA sessions will also be cancelled then?

Mahnoor_Wani_1I

Hi ! I agree with you that studying at home has been really challenging for many. I think the best tip is to make a schedule and stick to it. Schedule for when you are going to do homework, study, or attend UA sessions. Also when studying follow the 45 min rule. Study for 45 min and take a 10 min br...

Mahnoor_Wani_1I

While watching today's lecture, I was confused about the concept of delocalization vs localization. Can someone explain to what each terms means in terms of resonance structures. Also, why does the delocalization of electrons increases a molecule or compound stability?

Mahnoor_Wani_1I

I also had trouble memorizing the SI units. I think what helped me was this mnemonic: Tera – The Giga – Great Mega – Man kilo – king hecto – henry’s deca – daughter BASE – Beth deci – drinks centi – cold mili – milk micro – μntil nano – nine pico – pm and since the SI unit increases/decreases by 10^...

Mahnoor_Wani_1I

I did chemistry and LS30A homework for halloween

Mahnoor_Wani_1I

I think for ionization energy is that B is lesser than Be and O is lesser than N because of the half filled and fully filled orbitals of N and Be is more stable (require more energy to ionize an electron)

Mahnoor_Wani_1I

Sometimes next week, I'm pretty sure since yesterday was the last day everyone took a makeup midterm

Mahnoor_Wani_1I

434 nm is in the visible region so n=2 is the correct answer. For Balmer series, n=2 means the final energy level is 2. The electron would drop down to the energy level 2 after it becomes stable after exciting to some other higher energy level. The Rydberg Equation is frequency = R* ((1/n^2 for the ...

Mahnoor_Wani_1I

Yes it is during our TA discussion section but it will not be the same zoom link (another zoom link will be posted) If you have an external webcam, you can use that. If not, use a second device but make sure to use the zoom link provided on your TA Site for proctoring I'm not sure how many MC but ye...

Mahnoor_Wani_1I

19. During a summer camping weekend 4 moles of butane (C4H10) gas were used for cooking. Chose the right balanced equation for the combustion of 4 moles of butane gas. What is the net number of moles of gas produced? A. 4C4H10(g) + 26O2(g) → 16CO2(g) + 20H2O(g); 6 B. 4C4H10(g) + 26O2(g) → 16CO2(g) +...

Mahnoor_Wani_1I

Look at outline 1 + 2 on the Lavelle's website. It tell you exactly what you need to know!

Mahnoor_Wani_1I

My TA said we could use blank papers as scratch paper. Since the camera will be on, they will be able to see and approve your scratch paper.

Mahnoor_Wani_1I

The Debroglie equation tells us that wavelength = h/mv Since the question states that velocity (distance/sec) is equal to the wavelength, we substitute velocity for wavelength. V = h/mv Isolate the V V^2 = h/m V= sqrt(h/m) Plug in the planks constant and the mass of an electron, which is also a cons...

Mahnoor_Wani_1I

Here is my thought process (My value given for work function was different than yours): Given: the work function aka the threshold energy (3.200 x10^-19 J) We need to solve for max wavelength of E=hv function. Wavelength is inversely proportional to frequency. So max wavelength = min frequency. Min ...

Mahnoor_Wani_1I

Page C57 of the textbook in sapling includes the solutions to odd numbered exercises

Mahnoor_Wani_1I

What is the question asking you to calculate?

Mahnoor_Wani_1I

I think it because of the equation E=H*V. This equation shows that energy per photon is directly proportional to Frequency (V). So as frequency increases, energy per photon is higher. In addition, from the equation c= wavelength * frequency, frequency is inversely proportional to wavelength. So as f...

Mahnoor_Wani_1I

First step is to convert every units into SI units. In this case, we were only given 100 pm. Since the meter is the si unit, you convert it into m. (1 picometer = 10^-12 meter). THEN use the the formula for velocity ( v=h/mλ) to solve. h is a constant = 6.62626*10^-34 J*s m is the mass of the neutro...

Mahnoor_Wani_1I

In the SI system the unit for Kelvin is just K (make sure It is capital K). As for Celsius, it is °C . For Fahrenheit , it is °F. I think the reason why Kelvin doesn't have a degree may have something to do with the fact that this is an absolute scale

Mahnoor_Wani_1I

Could you possibly post the solutions for the problems? I want to compare my answers to see if I did it right. Thank you!

Mahnoor_Wani_1I

I have been looking up prices for webcam on amazon but all of them are above $35 and my budge is around $25. Anybody know where I can find a webcam for cheap price? if you purchased one, can you drop the link for the website below

Mahnoor_Wani_1I

To find the molarity of Na2CO3 you divide 2.111 grams of solid (the solid here is NA2CO3 since this is the solute in the aqueous solution) by its molar mass to find moles. Moles = Grams /molar mass
Then you do moles/volume to find the molarity

Mahnoor_Wani_1I

When we find the moles needed for each components of a formula, how should we arrange the equation? For example F1. We found the citral empirical formula has 10 carbon atoms, 1 oxygen atoms, and 16 Hydrogen atoms. In what order should we write the formula? Or does it even matter if we write in rando...

Mahnoor_Wani_1I

C. Number of objects (atoms) = amounts in moles x number of objects per mole (avogradros constant= 6.0221x10^23) In this case since they both contain the same number of objects (atoms), the amount in moles (aka number of moles of atoms) will both be equal. So the answer is both. You can try to plug ...

Mahnoor_Wani_1I

Heptahydrate means 7 water molecules. SO 7H20 Hepta= Seven Hydrates= a compound, typically a crystalline one like this epsom salt, in which water molecules are chemically bound to another compound (MgS04) or an element Basically anytime you see a hydrate you know that H20 is going to be in the formula

Mahnoor_Wani_1I

On Monday's office hour we just went over the syllabus. But I do recommend going to his office hours when you have time since he is going over materials/topics.
Also, to add on to that question, is the discussion from the Monday office hour the same as Thursday?

Mahnoor_Wani_1I

Personally, I like to take notes when reading the textbook materials. In my opinion, it helps me to remember what is important in each sections of a chapter and the important formulas.This is way when I am for the midterm/exam I don't need to look at the textbook and scroll down millions of pages to...

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