CHEMISTRY COMMUNITY

abby hyman

If someone could help me with this one I would be so appreciative! I have tried so many times and can't figure out what I am doing wrong so if you could use my numbers that would be great!!

abby hyman

I think Le CHatelier's principle would be one you would need to memorize for the midterm. Similar to how we had to remember Pauli Exclusion and Hund's rule ect.

abby hyman

As explained above, the chart with initial concentration, change in concentration, and equilibrium concentration is very helpful for this problem

abby hyman

Yes that would be the equation. It would be helpful for this question to set up the table to determine the values in terms of x and then can use the quadratic formula to solve for x

abby hyman

Can someone explain to me how you would be able to figure out the partial pressure of a gas if you are not given the temperature?

abby hyman

To begin, you would need to use the wavelength given (converted to meters) to find the velocity of the ejected electron. The equation for this would be deBroglie's so wavelength=planks constant/(mass)(velocity) Once you have the velocity of the electron, you can use 1/2mv^2 to find the Kinetic energ...

abby hyman

Coordination number is the number of bonds but you must keep in mind that some ligands are bidentate/tridentate/tetradentate ect and would contribute 2 or more bonds. These additional bonds must be taken into account to find the correct coordination number.

abby hyman

It does not matter really how you write it. I remember in lecture that Lavelle wrote it as OH2 to show that the oxygen was what was donating the electrons rather than the Hydrogen

abby hyman

I am starting by doing 10 problems from each section on the outlines and then checking them and the sections where I struggled I will go back and re-read the textbook section and try more problems.

abby hyman

Resonance structures are determined to be more stable because they represent delocalized electrons and the fact that they can be found in multiple places. In general delocalized electrons are spread out over the molecule which makes it more stable than if it was fixed location.

abby hyman

I think of hybridization in terms of the electron configuration where the hybridization orbitals are the combination of the orbitals with electrons in them

abby hyman

I find flashcards very helpful for this class in general. I have the name of a compound on one side and the lewis structure and properties on the other and write down what I think the answer is on a piece of paper and then check it with the back after.

abby hyman

I think the way that it is most similar to high school chemistry is in the fact that a lewis acid is electron-deficient and the lewis base is electron-rich and the electron-rich donates to the electron-deficient.

abby hyman

An amphoteric substance is one that is able to react as both an acid and a base. Amphiprotic is a substance that could accept or donate H+ ions.

abby hyman

NH3 is neutral because the N has a charge of -3 and each H has a charge of +1 creating an overall charge of 0 for the compound.

abby hyman

I do not think any questions would be asked in this class about what state of matter an atom or molecule would be in. Other than knowing that metals are solid and the obvious gasses, you should be solid

abby hyman

Yes in Lavelle's reviews he should talk about the format and details for the final but it should be the same format and set up as the midterms.

abby hyman

I believe it is the case that a ligand is a lewis base but all lewis bases are not ligands. A ligand is specifically the lewis base as part of a coordination compound.

abby hyman

Myoglobin is found in the tissues of the body while hemoglobin is found in the blood. They both serve the same purpose of transporting oxygen around the body but hemoglobin carried 4 times the amount of oxygen as myoglobin

abby hyman

For the s and p orbitals, you can use the group number to tell you how many valence electrons an element has, and for the d block, you can think about writing the halogen electron configuration and see how many electrons are written

abby hyman

This is so helpful. I was struggling with naming a lot and these videos helped me out a ton.

abby hyman

As stated, a coordination covalent bond connects a ligand to a transition metal ion. The ligand contributes both electrons to the transition metal which is why it is a coordination covalent bond.

abby hyman

I believe the fact that they are the same atom does not make a difference in this case. You have to take into account the bound atoms and lone pairs to determine the geometry

abby hyman

The reason that a molecule with 6 electron regions has an octahedral geometry is that the shape that is made in which the atoms would be the most stable is called an octahedron. This shape has 6 vertices which would represent the positions of the 6 electron regions. As for trigonal bipyramidal, a mo...

abby hyman

I think it is very helpful to know them and have them memorized.

abby hyman

I am doing pretty well. Finals feel more stressful this quarter than usual for some reason.

abby hyman

Hi I was wondering if anyone could explain to me how you would go about naming [Co (NH3)3Cl3]
I thought it would be triamminetrichlorocobalt(II)

abby hyman

Hey! So AsF3 has a tetrahedral arrangement but a pyramidal shape due to the fourth electron region being a lone pair rather than an atom. The tetrahedral arrangement means that there is a hybridization of the one S and three P orbitals which is why it is sp3. You can also think of it as s + p*p*p.

abby hyman

Hi can someone explain to me what it means that the acid donates protons to the base?

abby hyman

I have also used organic chem tutor on youtube! I found that really helpful.

abby hyman

He has not said how the final will be proctored. I assume it will be similar to the earlier midterms and I believe it is in the same multiple-choice format as the midterms.

abby hyman

As the person above said, you would be correct that seesaw geometry has four bonds and thus a coordination number of 4, it is not the most common geometry for molecules with four bonds.

abby hyman

The exceptions for the octet rule include examples such as SF6 where Sulfur can accommodate more than 8 valence electrons and BCl3 where Boron has less than 8 electrons in its valence shell.

abby hyman

No an A+ and A have the same GPA

abby hyman

Does anyone know if there is any way to review the ones you missed on midterm 2?

abby hyman

Don’t stress too much! The chemistry community points along with the homework make up a good portion of the grade and you can do better on the next tests!!

abby hyman

Anions are just atoms that gain electrons or become more negative to be in a more stable state. cations are similar except for they lose electrons or become more positive to reach a more stable state.

abby hyman

The number of valence electrons is found by going across the period of the element and counting how many. So carbon would be 4, oxygen 6 etc.

abby hyman

I found the text book problems, step up sessions, and workshops so helpful because you get to see most of the types of questions that will be asked on the midterm.

abby hyman

Yes, the number of spectral lines is equal to the number of possible transitions from n=7 to n=1. To find the wavelength range you just have to find the wavelength corresponding to the transition from n=7 to n=6 and the wavelength corresponding to the transition from n=7 to n=1. These would be the m...

abby hyman

To solve this, make sure you remember to convert nanometers to m in order to do the proper calculations. To find the frequency from the wavelength you would first use c= frequency/wavelength. Once you have the frequency, you plug it into the equation f= (Rydberg's constant) (1/n(final) - 1/n(initial...

abby hyman

I think there is a lot of information we will need to know requiring the orbitals. Mainly, it is important to be able to identify an atom from its ground-state electron configuration, (which is where the 2s and 3s come from). The periodic table is separated into blocks, corresponding to the type of ...

abby hyman

Yes, you have the right idea about it. since you do not want a coefficient to be 15/2 you have to multiply every coefficient by 2 so they are all in whole numbers and maintain the correct ratio

abby hyman

As they stated above, the wavelength and frequency do not change based on the number of photons. The value you get for energy is per photon so you must only multiply this value by 100 to get the total energy.

abby hyman

hey again kendall!! still missing you! Wish we were back in class with sam and brandee! I would love to do some midterm review over zoom with you! Text me and let me know when works best!

abby hyman

Hey Kendall! Miss you from last year's ls7b class! Do you know if the first midterm will cover weeks 1-3 only or if the beginning of week 4 is included?

abby hyman

Protons and neutrons have around the same mass of about 1.67 x 10^-24 grams while electrons are only 9.109 x 10^-28g. Protons and neutrons determine the mass of an atom, while electrons move from atom to atom without a significant change in mass

abby hyman

Although I believe for this quarter the exams are multiple-choice so it is not as important, usually, it is good to have your answers in 3 or 4 sig figs. Also, it does depend on the TA since they are grading but usually there is a range for the answers to account for rounding errors.

abby hyman

I think the problems on the audiovisual topics are the most helpful for studying. It is helpful to see many different problems for each topic so you will be prepared for the kinds of questions being asked on the midterm. Also, of course, it is important to have a good background for what you are doi...

abby hyman

I am assuming we can be muted for the exam as I have two roommates who would be using the space I would be taking the exam. My TA said that they want to be monitoring your workspace rather than your face. He recommended getting a webcam that would attach to your computer.

abby hyman

I would love to be part of the virtual study group my Instagram is _abbyhyman

abby hyman

The state of the molecule is not required for balancing equations right now. I believe Lavelle will discuss more of this later on in the quarter, but not something that is tested on I don't think.

abby hyman

Along with the conversion factor link on the website, I believe you are given some conversions on the formula sheet for tests.

abby hyman

I believe the periodic table is always provided to you if you need it for exams so memorizing would be unnecessary. It does save time to know the molar masses for some of the commonly used elements though, so you do not have to refer back every time.

abby hyman

Although the molecular formula is directly related to the molar mass of elements and the compound, there is not a common multiple that would take you from molar mass to molecular formula. If you meant how to get from empirical formula to molecular formula using the total molar mass, then you would a...

abby hyman

I believe for this class you just need to recognize the common ones but will not be asked to produce the name based on only the empirical formula.

abby hyman

I figure out which atom is the least electronegative which is often the one with the lowest ionization energy. Nitrogen and Oxygen are exceptions to this though

abby hyman

Polarizability is how easily an electron cloud is distorted by an electric field. Polarizing power is a cations ability to attract valence electrons from a nearby anion in ionic compounds

abby hyman

Sigma bonds are formed by end to end overlapping atomic orbitals. Pi bonds are when the lobe of one atomic orbital overlaps with another.

abby hyman

I agree with this. hydrogen bonds form only when hydrogen bonds with nitrogen oxygen or florine so D would be the only one that forms a hydrogen bond.

abby hyman

I also am wondering. My TA said that they have not written yet so do not know...

abby hyman

Atomic radius increases as you move from the top right corner of the periodic table to the bottom left. As you add more electrons the radius increases until a new shell is added when you move down to the next period

abby hyman

The Rydberg formula is a mathematical formula used to predict the wavelength of light resulting from an electron moving between energy levels of an atom.

abby hyman

The difference between ionic and covalent bonds are the type of element involved in the reaction. Ionic bonds are between a metal and a nonmetal while covalent bonds are between two non-metals.

abby hyman

The online modules and assessments are so helpful for this class you can really see if you understand the material. I have found youtube videos helpful as well for more knowledge on sections I do not understand.

abby hyman

The pre and post assessments on the class website are very helpful for studying as well as the module videos.

abby hyman

Nonmetals do not form cations because their ionization energy is too high, they share electrons to form covalent bonds

abby hyman

Formal charge indicates the gain or loss of electrons while forming covalent bonds. Used to find which is the most stable

abby hyman

ionic bonds are between a metal and a non-metal and covalent are between two non-metals

abby hyman

electronegativity increases as you move left to right and decreases as you move down on the periodic table

abby hyman

My TA said there will be material from test 1 on the midterm, but test 2 is from after the midterm to the test and then the final will be comprehensive from the first test on

abby hyman

Drake Choi_1I wrote:Is there going to be a curve for the midterm? Or is grade based on raw score?

No curve in the class so just your raw score from all assignments added up out of 500 I believe

abby hyman

since wavelength is a measure of distance it is found in meters, pm, or nm

abby hyman

When studying by doing practice problems from the textbook, how do you guys check if your answers are correct? For me many times I may think I got the correct answer when I really didn't. There is a solution manual for the textbook questions so you can check if you did the work correctly that way! ...

abby hyman

The unrealistic answer tells us that the electrons cannot be located at the nucleus of the atom, because the value we used for the uncertainty in position for the calculation was the diameter of the hydrogen nucleus. This tells us that electrons cannot be located in the nucleus, and therefore are o...

abby hyman

I am also very confused on this topic and how to tell if they are parallel or paired?

abby hyman

Claire Grover 3G wrote:∝ is the sign! Basically instead of writing E = hv, you could write E ∝ v, which means that E is proportional to v (by a factor of h).

I agree with this. This shows that E and v are proportionate to each other.

abby hyman

Wendy Perez 3A wrote:I believe that Dr. Lavelle mentioned this once in his lectures. A bond length between two molecules is about 10^-10m, which is equal to 1 Angstrom.

Yes, this is correct. A bond length is always equal to 1 angstrom

abby hyman

Since you have to have a mass to find wavelength using DeBroglie's equation, it would be impossible for it to work for light because light has no mass.

abby hyman

I agree with the statements above. In De Broglie's formula, since you are dividing by mass to get wavelength, the inverse relationship would make the wavelength smaller as the object gets bigger in mass.

abby hyman

My TA informed us on Monday that if we have the correct answer we get full credit, but if we don't have the correct answer we can get partial credit if the work we've shown is correct but a calculation was messed up

abby hyman

You should only use sig figs in your final answer to avoid error and not have incorrect numbers in your final answer.

abby hyman

The states of matter do not matter when balancing a chemical equation

abby hyman

Personally, I like using the 100 g method because if there is such a question that says " there is 40%C, 10%O, 20%H, and an unknown amount of a 4th element, it makes it way easier to go from there inorder to calculate the empirical formula. I agree with this, the 100 g method is the easiest be...

abby hyman

My TA said the same, the common ones that we've been using in class and such will be used but for the most part, we will be given them.

abby hyman

My TA said the same, the common ones that we've been using in class and such will be used but for the most part, we will be given them.

abby hyman

Johnathan Smith 1A wrote:Can someone clarify exactly what we are supposed to do for Homework? Are we doing five problems overall or five from each section?

For the homework, you only need to turn in five problems overall, the list of questions in the different sections is just the array of questions to choose from.

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