CHEMISTRY COMMUNITY

Manav Govil 1B

This is a helpful link if you're confused!

https://www.khanacademy.org/science/che ... r-small-kc

Manav Govil 1B

This was a bit of a tricky question - much due to the fact that we did not know what buffers were! Buffers have a region where the pH does not change as much despite adding acids or bases. The way to make a solution decrease in pH is by adding more acidic compounds, so one would need to identify the...

Manav Govil 1B

Test 2 is a good review for Electrochem. I was pretty surprised about the last question! I didn't know that the electrode size in the anode doesn't matter!

Manav Govil 1B

Comparing pKa/pKb with pH/pOH will be important to know how to do on the final - I think! See...pKa = -log(Ka), so the higher the pKa, the lower the Ka. Ka = \frac{[A-][H+]}{[HA]} Lower Ka means higher products - and lower H+ pH = -log(H+), which means the higher the pH, the lower the H+ Therefore, ...

Manav Govil 1B

How do we calculate the pH of a buffer solution? Are there any good videos explaining this? We only have to calculate the pH based on the ice table example used in the notes. Exactly! But the Henderson-Hasselbach Equation is a shortcut that lets us skip the ICE table entirely! The equation can only...

Manav Govil 1B

If you are struggling with the Nernst equation, I suggest watching this video:

https://www.khanacademy.org/science/che ... t-equation

It's pretty helpful!

Manav Govil 1B

You will need to use the Nernst equation for most concentration cell questions, especially for finding Ecell or a concentration of a half-cell. Just like the comment before this one says, E°cell = 0, and we have to apply this information to get more information.

Manav Govil 1B

Platinum is usually included when there is no electrode available to drive the reaction.

Manav Govil 1B

In any sort of chemistry, a reaction is spontaneous when it has enough energy to go to completion and to be released (or when the energy required to break bonds is less than the energy required to form bonds). This is also present in redox reactions.

Manav Govil 1B

This is not a question, but a mere epiphany I had while studying for the second chem test! Does anyone remember the activity series from high school? I sure didn't until a few hours ago. For those of you who don't remember, or have never seen one, here is a link to one: https://s2.studylib.net/store...

Manav Govil 1B

I would say that Le Chat applies to E-cell. For example, if you increase the concentrations of reactants, more products will form, and more reactants will be oxidized. In a cell ... I'm not sure if the reverse can occur.

Manav Govil 1B

You don't have to use platinum, but platinum is the best solid conductor to use for this class. There are other solid conductors out there that can be used in these reactions, and if the question wants you to use them, they will provide the data for them.

Manav Govil 1B

Also, the max potential is when no voltage has passed.

Manav Govil 1B

There is no left or right in determining what an anode or cathode is. You should know that the anode is the part where things get oxidized and the cathode is the part where things get reduced. They may try to trick you on the test by switching the positions of the anode and cathode.

Manav Govil 1B

I found this site helpful when learning about the function of a salt bridge, which is to make sure that only electrons provide the energy to the system.

https://chemistry.stackexchange.com/que ... re-be-used

I hope this helps!

Manav Govil 1B

Oxidizing agents are reduced.
Reducing agents are oxidized.
These get tricky because what they do is opposite of what their names imply. It almost got me on my recent LS7A midterm, haha.

Manav Govil 1B

The oxidation numbers for metals in their natural states are their charges, I believe.

Manav Govil 1B

Autoprotolysis is simply the proton transfer between two identical compounds, such as water, weak acids, etc.

Manav Govil 1B

If you are referring to problems with ka, then there will usually be a step where you can ignore the x, so that a cubic will not be needed to be solved. We cannot solve cubics without a graphic calculator.

Manav Govil 1B

Additional inert Gases don't cause a shift in equilibrium, as they are not necessarily part of the reaction.

Manav Govil 1B

We are given the entropy values we need to know for the exam on the equation sheet as they did for the midterm. We will not know or use the entropy values that are not proved on the equation sheet.

Manav Govil 1B

Delta H can usually be written as q. This is derived from the equation $\Delta H = \Delta U + P\Delta V$ . $\Delta H = q + w -w = q$ , so $\Delta H = q$ .

Manav Govil 1B

You've got to remember that temperature does not increase when the heat is added during a phase change. Therefore, we cannot include it in the regular $q = nC\Delta T$ equation, which is why we multiply the heat inputted by the moles and use that to calculate the delta H Fusion.

Manav Govil 1B

I used https://www.thoughtco.com/intensive-vs- ... ies-604133 when I was studying for my exam.

Manav Govil 1B

I thought that the posts were monitored via MyUCLA since we have to sign-on every time we post on Chem community. Therefore, as long as you have posted at least 5 times by Sunday 11:59 PM, you should get the five points of participation credit for said week.

Manav Govil 1B

I believe that the heat energy inputted into the system at that time is there to break or form the bonds, transitioning the state of the sample.

Manav Govil 1B

An increase in heat energy is not the same thing as an increase in temperature (delta H is different than T). Therefore it is possible for heat energy to be introduced to the system and for the temperature to not increase.

Manav Govil 1B

Burning fossil fuels leads to an increase in carbon emissions, leading to effects such as global warming. Is this important to know for this course?

Manav Govil 1B

Only in the world of chemistry can a Pb & J sandwich kill you. Unless you're allergic. Then you're also dead.

Manav Govil 1B

Extensive properties depend on the sample size, such as mass and volume. Intensive properties, on the other hand, do not depend on the quantity of the sample we are looking at, such as the melting point of a sample. Samples with extensive properties can be calculated by subtracting the final amount ...

Manav Govil 1B

Equilibrium constant does not change (it only changes if temperature changes), but the equilibrium will shift in such a way that the equilibrium constant remains the same after calculation.

Manav Govil 1B

The inverse is also true. If the pressure is decreased (more volume available in the system), the equilibrium will shift towards the side that has more moles.

Manav Govil 1B

You should be able to tell if something is a weak acid or base, based on if it can accept a proton or not. Also, you should have the strong acids memorized.

Manav Govil 1B

If you still haven't picked up your final exam, don't fret! They still have them until the end of the quarter ... but its best to pick them up ASAP.

Manav Govil 1B

Aren't reversible reactions where the reactants can go towards the products and the products can go back toward the reactants, like weak acid and base dissociation? That would mean that irreversible reactions would only go in one direction (from reactants to products), such as combustion reactions. ...

Manav Govil 1B

Also, if you are given the concentration and need to convert into bar, torr, etc., you would use the PV = nRT equation with the corresponding R.

Manav Govil 1B

Also, solids and liquids are NOT affected by pressure.

Manav Govil 1B

Honestly, I would just read the chapter and do the problems before the lecture, so that we know what he is talking about in the lecture - making it easier to understand.

Manav Govil 1B

State functions are any functions that can be derived by subtracting the final result by the initial result.

Manav Govil 1B

The system is the area where the reaction is occurring. The surroundings are the outside of where the reaction is occurring. Think of the reaction happening in a beaker. If the reaction is endothermic, it requires energy to come to fruition. Therefore, it will take energy from the surroundings, or o...

Manav Govil 1B

The solid would not matter when setting up the ICE table. The products do matter. What I do is cross out the section for the reactant, and add x to both the products. Then, you can solve using k.

Manav Govil 1B

The pH scale is not restricted per se, but it is at room temp. I don't think that they will ever ask you a question where the answer is pH 15.45 though. Oh, and pH can never be negative.

Manav Govil 1B

Yeah, it is everything in outlines 1 and 2. Make sure you know the ICE table, Le'chat, and how to manipulate the important equations, Also, pH is very important.

Manav Govil 1B

Think about it. We are focusing in on an equilibrium reaction between concentrations or gases. If we were to take in account for solids and liquids, we would have to take into account another form of k - muddling up the equation.

Manav Govil 1B

We can use the equation to relate the values before and after the reaction, like comparing pressure, volume, and concentration.

Manav Govil 1B

I feel like K>10^3 and K<10^-3 is the absolute bounds for the favoritism of the reaction.

Manav Govil 1B

The long way is comparing the K with the newly made Q that occurs after Le Chat occurs. We do this by calculating the equilibrium constant K and Q, see which one is greater, and decide whether the reaction shifta to the left or right. The quick way is by simply looking at the reaction and counting t...

Manav Govil 1B

Le Chatelier's Principle is a way to make sure a reaction stays at equilibrium when a different force, such as pressure or volume, is altered.

Manav Govil 1B

In ICE tables (which we will learn about later), we ignore solids and liquids and only worry about aqueous solutions and gases. Would the ideal gas law be relevant to why we ignore those two states?

Manav Govil 1B

K is the equilibrium constant, which can be measured by either comparing the concentrations of the reactants and the products in the reaction, or the partial pressures of the reactants and products in the said reaction. Since K is a constant, whenever it is used (as Kc or Kp), it should equate. With...

Manav Govil 1B

The filling of the octets is the most important aspect - double and triple bonds come in later. Double bonds should be used when both the central and attached atom has an extra lone pair each, and if the formal charge conditions are most favorable. I am not sure what you are talking about regarding ...

Manav Govil 1B

Actually, the Cl would have the hybridization of sp3.

Manav Govil 1B

Cisplatin is for cancer prevention. On Marshmallow, this explanation was posted: Chemotherapy drug, Cl on same side are involved in the binding of cisplatin to Guanine base pairs in DNA that are adjacent or near each other. The binding at 2 base pairs allows cisplatin to block DNA replication machin...

Manav Govil 1B

I am not sure what you mean by "going both ways", but you would name a coordination compound by starting off by the ligand names in alphabetical order. Then you would write down the cation names in alphabetical order. Finally, if there are any anions, you would write them at the end.

Manav Govil 1B

We would look at the naming chart Lavelle provided us and write out the formula. Then using that formula, we would draw the structure.

Here is the naming chart:
https://lavelle.chem.ucla.edu/wp-conten ... pounds.pdf

Manav Govil 1B

For my exam, I simply labeled each bond as a sigma bond and each double bond with an extra pi bond. That was the correct way to do it, which means you probably got full points unless you accidentally missed one.

Manav Govil 1B

Certain questions may ask for all hydrogen bonding sites, which would be all the lone pairs and hydrogen bondings to N O and F in a molecule.

Manav Govil 1B

Not all atoms can create ionic bonds, but I believe that they all can be ionic to a point.

Manav Govil 1B

Sigma bonds are formed when two molecules share electrons. Ionic bonds do not share electrons - but exchange them. Therefore, bonds such as NaCl do not form sigma bonds.

Manav Govil 1B

Now, when multiplying two or more numbers, it is important to have the final answer in the form of the smallest sig figs. Values found on the periodic table do not count in this sig fig process. Values found through calculation or in the problem count as sig figs. If the sig figs are not clear, it i...

Manav Govil 1B

The IUPAC naming system is used in organic chemistry. I believe that we have the freedom to choose which naming scheme we use in this class. BUT, we will need to have memorized the naming scheme. We will not be provided anything on the test. I believe that is how it works.

Manav Govil 1B

Probably naming compounds that he gives to us on the test. It can also be part of a problem where you have a specific compound that you have just used VSEPR for in finding the shape, lewis structure, etc.

Manav Govil 1B

Oxidation numbers are rules that you need to memorize. The following link is from Khan Academy regarding identifying Oxidation numbers. It is pretty helpful. https://www.khanacademy.org/science/chemistry/chemical-reactions-stoichiome/types-of-chemical-reactions/a/oxidation-number I really do hope th...

Manav Govil 1B

There are many examples of biological coordination compounds, like chlorophyll or hemoglobin. I think that you find the following website helpful:

https://chemistrynotesinfo.com/coordina ... -class-12/

I hope this helps!

Manav Govil 1B

I suggest reading the comments. Honestly, after reading what others have to ask, I realize that there are certain topics that I had forgotten to study. It is indeed a helpful tool.

Manav Govil 1B

The surface area of the shape is important when it comes to dipole moments. If the two molecules expose more surface area to one another, then they have more London attractions. The molecules will be highly polarizable and have a greater intermolecular force than two molecules that expose less surfa...

Manav Govil 1B

Negative charges tend to be put on the more electronegative atom, while the positive charge is put on the atom affected by the electronegative atom. Look at SO2. There is a negative charge on the Oxygen (the more electronegative atom), and a positive charge on Sulfur (the element affected by the ele...

Manav Govil 1B

Exactly. Look at CO for example. The lewis structure would indicate a triple bond between the two atoms. If we are to fill the octet correctly, the final formal charge for Oxygen is +1 and the final formal charge for Carbon is -1. These two cancel out to 0, which is the overall charge of the molecule.

Manav Govil 1B

For the question right above this comment:

Exactly. Atoms such as fluorine and oxygen are highly electronegative and are able to pull electrons closer to themselves. Putting a negative on them only makes sense because they have a natural tendency to be negative in a molecule.

Manav Govil 1B

Pi bonds are also more commonly found in double and triple bonds, while they are not included in single bonds. Pi bonds add bond strength to the bonds - hence why double and triple bonds are stronger than single bonds. All types of bonds have sigma bonds.

Manav Govil 1B

Only N, C, F and O follow the octet rule. The exceptions are when radicals are involved.

Manav Govil 1B

Although N and O have favorable bonds, certain structures require them to have more or fewer bonds - causing them to have a charge. For example, NO+ shows a triple bond between the N and the O. The N is pleased with a formal charge of 0, but the O has a formal charge of +1, which causes the positive...

Manav Govil 1B

This is more of an organic chemistry topic when you have to draw resonance structures regarding radical molecules. In orgo, the radical is most commonly found on the C, but in general, any atom can exhibit a radical. Radicals are notable when they appear on structures that should have their octet fi...

Manav Govil 1B

It is best to have the negative charge on the most electronegative atom in the molecule, and the positive charge on the least electronegative atom in the molecule.

Manav Govil 1B

Think about it. There were some long questions, and because we had to write in pen - much of it would be messy. I would be surprised if we get our grades back before next week. Also, I think that we will get the papers back, as it had a scoring sheet for the students to see, and we were allowed to t...

Manav Govil 1B

You have to remember the scale for covalent vs ionic character. If the difference between the electronegativities of the two atoms are less than 1.5, then it is a covalent bond.

Manav Govil 1B

Also, the more formal charges there are that equal to zero, the more stable the molecule actually is.

Manav Govil 1B

Hybrid structures are just resonance structures interpreted through one diagram. The double bonds are represented as one solid and one dotted, and there are enough electrons on each atom considering a double bond is present. Any bond can have resonance.

Manav Govil 1B

If you are looking at examples such as ONF from question 2B.1, you would see that to get a zero formal charge, O needs two bonds, N needs three, and F needs 1. Since N has the most bonding possibilities, N would be the central atom, and the O and F would be around it.

Manav Govil 1B

You can also try checking the formal charge. If we were to put a double bond between the N and the F, and a single bond between the N and the O, the formal charge for F would be +1, and the formal charge for O would be -1. This is worse than the zero formal charges across the board when the double b...

Manav Govil 1B

Cerium is actually the first element in the Lanthanoid f-block, giving it the configuration: [Xe] 4f1 5d1 6s2. Lanthanum is part of the d-block with a configuration of [Xe] 5d1 6s2.

Manav Govil 1B

Think of it like people around a campfire. The people close to the campfire will receive the most warmth, will people farther away won't receive as much. Therefore, the people farther away are more likely to go to a different fire where they get more warmth. The people close to the campfire are the ...

Manav Govil 1B

I don't think so, but it is an interesting concept to think about.

Manav Govil 1B

Why don't we compare the periodic trends for radioactive elements? For example, according to the trends, Francium should have a larger atomic radius than Caesium, but we don't mention Francium or any other group 7 elements for that matter. Also, how do we compare the trends for the Lanthanoids and a...

Manav Govil 1B

The electrons would not collide with one another, but repel each other when they get close, shifting into a different spin. I think that is what happens, but I'm not a 100% sure.

Manav Govil 1B

I believe that the test might be more calculation heavy, but have parts where we might need to explain a certain circumstance such as explaining the trends. I took AP chem, and that is what we had to do. I acknowledge this class may be more difficult, so it might adopt a different formula for tests,...

Manav Govil 1B

My main way of studying is reading the entire chapter and then doing all the homework problems. If I do not understand any of the homework problems, I either go here, or go to my TA. If there is something I do not understand, I seek out help.

Manav Govil 1B

Nice explanation!

Anyway, these are what I got:

a. 1 orbital
b. 5 orbitals
c. 3 orbitals
d. 7 orbitals

Manav Govil 1B

I got this:

a. 3
b. 1
c. 4
d. 1

I just wrote the number of orbitals.

Manav Govil 1B

This is what I got after doing the question:

b. There are five values: 2, 1, 0, -1 and -2

c. There are three values: 1, 0 and -1

d. There are four subshells: 4s, 4p, 4d, and 4f

I hope this helps.

Manav Govil 1B

A +1/2 spin is spinning up, while a -1/2 spin is spinning down. Remember, this is not like the electron is spinning north or south if it is spinning up or down. They are spinning in different directions. That's about it.

Manav Govil 1B

We should know where to apply the equation and how to use it, but not the specific experiments of history behind it. Tests - based on the first one - are more calculation based rather than history-based.

Manav Govil 1B

From Lavelle's website: "Each test and exam has a total score but is not assigned a grade. Only at the end of the class when the class average score (out of 500 points) is known are final grades assigned. This class does not use a curve. Group learning (Chemistry Community, Study Groups, Peer L...

Manav Govil 1B

The equation helps us calculate the energy of light. Planks constant has the units: J*s, which cancels out with the frequency units: 1/s. It helps us find the energy in J (Joules).

Manav Govil 1B

I love polar vs nonpolar stuff! The polarity of a compound depends on the charges and electronegativity of its structure. The electronegativity of atoms can be found on a periodic table such as this: http://www.thecatalyst.org/electabl.html Using the values from the periodic table above, you can mea...

Manav Govil 1B

Planck's constant is not really explored in depth in high school/college chem. If you would like to learn about the history of Planck's Constant, I recommend this Wikipedia article:

https://en.wikipedia.org/wiki/Planck_constant

Manav Govil 1B

If you're interested in frequency, I recommend reading the Wikipedia page behind it:

https://en.wikipedia.org/wiki/Frequency

v (or nu) can also be expressed in Hz (Hertz), which is pretty interesting.

Manav Govil 1B

Manav Govil 1B

The molar mass from the periodic table does not affect our calculations, but the molar mass we get from a question or from our calculations do affect our calculations.

Manav Govil 1B

I posted this on another thread...so here is a copy:

What tricks me up the most is the zeroes involved in sig-figs. I'll show you why:

250000 has 2 sig-figs
250000. has 6-sig-figs
250.000 has 6 sig-figs
250.001 has 6 sig-figs
1.00025 has 6 sig-figs
0.00025 has 2 sig-figs

Search found 104 matches