CHEMISTRY COMMUNITY

AdilaAhmed3I

Dinitrogen pentoxide, N2O5, decomposes by first-order kinetics with a rate constant of 3.7×10−5 s−1 at 298 K. (a) What is the half-life (in hours) of N2O5 at 298 K? (b) If [N2O5]0=0.0567 mol⋅L−1, what will be the concentration of N2O5 after 3.5 h? (c) How much time (in minutes) will elapse before t...

AdilaAhmed3I

Thank you to everyone who joined us today!!! It really meant a lot to us that so many of you showed up and hung out with us! Thank you to all of our performers and all of you are so talented and brought tears to my eyes multiple times throughout the karaoke session. Also big thank you to Dr. Lavelle...

AdilaAhmed3I

I didn't realize how bad I was at studying at home. Prior to quarantine, I would be literally anywhere else but at home to study. Other than that, I want to go on food dates with all my friends so bad because I know LA has all the good food locationsT_T

AdilaAhmed3I

A suggestion I have would be to approach the topics conceptually first. This would entail learning the fundamentals without any calcs first. Personally, understanding the conceptual ideas for all of the topics first makes it easier to create a pathway to approaching a problem. Additionally, Dr. Lave...

AdilaAhmed3I

Electrochem and Kinetics are probably my favorite because for me, they were the easiest to visualize and grasp. I also like drawing the half cells for electrochem :)

AdilaAhmed3I

No problem! It is really easy to mess up a balancing equations problems so definitely take your time, go step by step, and always make sure to check your equation after to make sure that it is balanced.

AdilaAhmed3I

Your basic set up should like this:

Fe + O2 +H2O--> Fe2O3∙ 3H2O

You should not need any electrons in this equation because you could just balance it from this equation. So first balance the Fe and then the H2O. After balancing those, then you can balance the oxygens.

AdilaAhmed3I

Electrolytic cells usually pertain to nonspontaneous reactions and are cells that require energy from an external source which causes the nonspontaneous redox reaction to occur. So you can say that these reactions are forced to occur by an input of electrical energy (this process is called electroly...

AdilaAhmed3I

Here's the steps I use: 1. Balance elements other than O and H 2. Balance O using H2O 3. Balance the Hydrogens using H+ 4. Check the overall charges on both sides and add electrons to the side with the greater positive charge to balance the overall charges 5. Combine the reactions by multiplying the...

AdilaAhmed3I

We hope to see all of you there for a fun karaoke session!!!

AdilaAhmed3I

You should not have any parantheses around the hydrate so just 2Fe2O3 . 3H2O

AdilaAhmed3I

Could someone help me out with this problem? I thought I understood it but I keep getting it wrong. Maybe I'm overthinking it. Thanks! It reads: Write a balanced overall reaction from these unbalanced half-reactions. In⟶In3+ Cd2+⟶Cd First is balancing the half reactions themselves using electrons: ...

AdilaAhmed3I

Please help. Identify the oxidizing and reducing agents in the skeletal (unbalanced) reaction. Then, balance the reaction, including the phase (solid, liquid, etc.) of each species. The reaction takes place in basic aqueous solution. Cl2O7(g)+H2O2(aq)⟶ClO2−(aq)+O2(g) First thing it to look at the o...

AdilaAhmed3I

Hello, I was wondering if someone could remind me exactly what determines whether the forward or reverse reaction is favored when doing Gibbs Free Energy calculations that indicate whether delta H or delta S will dominate? First, when looking at Gibbs free energy alone, a negative value for delta G...

AdilaAhmed3I

I'm planning on taking Chem 30A, LS 7A, an Honors class, and CompLit 2DW

AdilaAhmed3I

Hi, so for an inert conductor, are there other elements that are commonly used besides Pt that we should look out for? Also should it be on the cathode side when drawing the cell diagram or does it not matter? If it does, I was wondering why it should be on the cathode side? Thanks! While Pt is one...

AdilaAhmed3I

https://preview.redd.it/hnny0f5qsy431.jpg?width=1280&format=pjpg&auto=webp&s=5e76a429b305684737e13c99190944211353f13e Here's a picture to refer to. An anode is where the anions will flow towards and the cathode is where the cations will flow towards. The salt bridge will contain some com...

AdilaAhmed3I

Calculate the reaction Gibbs free energy of N2(g)+3H2(g) ->2NH3 (g) when the partial pressures of N2, H2, and NH3 are 4.2 bar, 1.8 bar, and 21 bar, respectively, and the temperature is 400.k. (b) Indicate whether this reaction mixture is likely to form reactants, products, or is at equilibrium. I u...

AdilaAhmed3I

This is so true!!! I used to (and still do sometimes) be so hard on myself for making those little mistakes. I would somehow feel worse making those mistakes than missing a question I just did not understand. With coming to college I realized that they're inevitable and now to combat any of those ha...

AdilaAhmed3I

I believe that may be a typo because if you look at where they actually calculate delta G they use subtraction rather than addition.

AdilaAhmed3I

The answer for part a is 145 KJ.

heres the atkins solution manual:
https://www.saplinglearning.com/ibiscms ... d=14921502

AdilaAhmed3I

I definitely think with this midterm, understanding the concepts and fundamentals will help because if you can understand the concept being asked you can already formulate some form of an answer. Like take entropy for example, if you read the question and let's say it dictates a situation where entr...

AdilaAhmed3I

The way I did this question was by kind of ignoring the vaporizations and solely looking at the substances themselves. When thinking of entropy, i think of disorder and how we can take one part of a substance and move it around. So for example, if we take C4H10, we can take one Hydrogen and put it i...

AdilaAhmed3I

In this question you are finding the heat capacity (calorimeter constant) of the calorimeter not necessarily the two different substances since they are using the same calorimeter. This means that in this calorimeter it takes x amount of energy to produce a unit change in temperature. So regardless ...

AdilaAhmed3I

To do this question, you are going to use
delta S = n Cv ln(Tf/Ti)

You are provide with Cv and the temperatures but you are not given n or moles so you can use PV=nRT to find moles. Once you find moles, then just plug in and solve.

AdilaAhmed3I

Melissa Solis 1H wrote:What are some examples of the isothermal process?

An example of an isothermal process is a refrigerator because the temperature inside remains basically constant for any of the changes that occur in it.

AdilaAhmed3I

I don't quite understand the 3rd law of thermodynamics. Could someone give a summary or basic explanation of what we need to know about it? Thanks! The third law states that the entropy of any pure, crystalline substance at absolute zero is 0. Entropy refers to the dispersal of matter and energy or...

AdilaAhmed3I

PART A: At constant volume, the heat of combustion of a particular compound, compound A, is −3822.0 kJ/mol. When 1.705 of compound A (molar mass =121.63 g/mol) is burned in a bomb calorimeter, the temperature of the calorimeter (including its contents) rose by 6.535 ∘C. What is the heat capacity (c...

AdilaAhmed3I

n ice cube with a mass of 50.0 g at 0.0 ∘C is added to a glass containing 388 g of water at 45.0 ∘C . Determine the final temperature of the system at equilibrium. The specific heat capacity of water, Cs , is 4.184 J/g⋅∘C , and the standard enthalpy of fusion, ΔH∘fus , of water is 6.01×103 J/mol . ...

AdilaAhmed3I

They should provide you with the context of the reaction. I think those problems said delta Hc which means enthalpy of combustion. That means that the three chemicals undergo combustion reactions which is where the chemicals react with O2 to either form CO2 and H2O or H2O alone. Once you have made a...

AdilaAhmed3I

They simply factored out that negative. Your set up is correct and will get the same answer

AdilaAhmed3I

They both will lead to the same outcome of the species being protonated. I would try not to confuse yourself with the changing pKa or pKb. If it said that the salt reacted with water then you have to change it to account for hydrolysis but in this case you will still get that the protonated species ...

AdilaAhmed3I

If you have a pH<pKa (pKb) situation, then the species you are looking at is in a more acidic environment where the [H+] is higher. This means that the species will tend to act more like a base and accept a proton from its surrounding, leading it to become a protonated species. So this is either HA ...

AdilaAhmed3I

In problems 9 and 10 of sapling week 2, it asks us to determine the predominant species for a weak acid and weak base by comparing the pH and pKa of the solutions. Can someone please explain how to do this? Thanks! A good way to think about it is by remembering [H+]. If you have a pH<pKa (pKb) situ...

AdilaAhmed3I

Hey, I am having trouble with this problem: HClO is a weak acid ( Ka=4.0×10−8 ) and so the salt NaClO acts as a weak base. What is the pH of a solution that is 0.074 M in NaClO at 25 °C? I solved it using Ka but it said that I got it wrong because I used Ka instead of Kb. Can someone please explain...

AdilaAhmed3I

I think you should first find where you are struggling in because you won't get anywhere until you understand the fundamentals behind the concept you struggle in. Definitely doing textbook problems would help find those areas and even going to different sessions will help as well. I like to watch yo...

AdilaAhmed3I

Hello, I am having a bit of difficulty understanding how to use the ice box and was wondering if someone could explain how I would use it in these chemical equilibrium problems? So an ice box is used for weak acids or bases that do not completely dissociate. There are three sections to consider: th...

AdilaAhmed3I

Hi! I had a question regarding 4D.15 in the textbook: Determine the reaction enthalpy for the hydrogenation of ethyne to ethane, C2H2(g) + 2H2(g) --> C2H6(g), from the following data: delta Hc (C2H2,g)=-1300 kJ/mol, delta Hc (C2H6,g)=-1560 kJ/mol, and delta Hc (H2,g)=-286 kJ/mol. Why couldn't we ju...

AdilaAhmed3I

First we shall determine what state the chemical will be in, protonated or neutral. For this we have to look at the pKb and pH. If the pH < pKb, then the protonated species will be more prominent. The chemical is in a more acidic environment which means that there is a higher [H+] present. Rather th...

AdilaAhmed3I

Hi, I was wondering if someone could explain how they solved this problem? Thank you! So for this question, we would utilize Hess's Law, which is basically adding equations (steps) to form the final equation. So you want to manipulate the equations so you get N2O5 as the product. If we take: 2NO+O2...

AdilaAhmed3I

I don't know why but watching 90s romcoms always puts me in a good mood (especially Clueless). A more recent one is Brooklyn 99 and I find myself rewatching it whenever I need a break.

AdilaAhmed3I

We went over this problem in my discussion section so I'll show it the way my TA did it. So H2SO4 is a polyprotic acid meaning that it can basically lose multiple protons (H+). So for instance, H2SO4 <--> H+ + HSO4- would be one deprotonation of the acid and this is the equation my TA used. You woul...

AdilaAhmed3I

Hess's law essentially states that the delta H for a reaction is the same whether it occurs by one step or a series of steps. What this means is that you can add the delta H's for multiple reactions together to get the overall delta H. For sapling, we did not necessarily use Hess's law. It was more ...

AdilaAhmed3I

Hello, I believe I may be getting my variables mixed up, but I was wondering if the equilibrium constant Kc and the reaction quotient referred to the same value? The Kc value is the ratio of the concentration of product(s) over the concentration of the reactant(s) AT EQUILIBRIUM. Kc is only for sit...

AdilaAhmed3I

Hello, I am having a bit of difficulty understanding how to use the ice box and was wondering if someone could explain how I would use it in these chemical equilibrium problems? So an ice box is used for weak acids or bases that do not completely dissociate. There are three sections to consider: th...

AdilaAhmed3I

19. Calculate the reaction quotient, QC, from the following equilibrium data collected in a 3.00 L sealed reaction vessel for the reaction: AsH3 (g) ⇌ As (s) + H2 (g) AsH3 = 5.55 x 10-4 mol, As = 3.31 x 10-3 mol, H2 = 1.23 x 10-3 mol. I know this seems like an easy problem but for the life of me I ...

AdilaAhmed3I

14A was teaching the fundamentals of chemistry and you need that as a basis for what is taught in 14B. Most of chemistry is building on past knowledge and content so what we learned in 14A will be making appearances in certain topics.

AdilaAhmed3I

Hi! I am wondering if there is a way to solve this kind of question without doing it the long way (aka using the quadratic formula): 26. A mixture initially consisting of 0.250 N2 (g) and 0.500 M H2 (g) reacts to form NH3 (g) which is 0.15 M NH3 (g) at equilibrium. Calculate the concentration of N2...

AdilaAhmed3I

What do partial pressures really mean? Why can they be converted to concentrations? I'm just not quite understanding what the term means. The pressure of a mixture of gases is the sum of the partial pressures of the different gases in the mixture. So we're basically saying that all the gases in the...

AdilaAhmed3I

At a certain temperature, 0.780 mol SO3 is placed in a 1.50 L container. 2SO3(g)↽−−⇀2SO2(g)+O2(g) At equilibrium, 0.160 mol O2 is present. Calculate Kc Could someone walk me through how to solve this? Thank you! I keep getting the wrong answer. The first thing you should do is convert everything to...

AdilaAhmed3I

For this question we would use the equilibrium constant expression
K=[Br]^2/[Br2]
We are provided with K and [Br2] so all you need to do is plug them in and solve for [Br]. The answer should be C.

AdilaAhmed3I

You would find it the same way as a normal compound. Although transition metals can have more than one possible oxidation state, the formula will reflect the oxidation state it is in. For example, if you have FeCl3, then you would find that iron has a +3 oxidation state. Similarly, if you are given ...

AdilaAhmed3I

what do you call a prisoner that makes jokes?
a silicon

AdilaAhmed3I

I’m probably going to sleep a lot and catch up on some reading and shows.

AdilaAhmed3I

pKa is a property of a compound that tells us how acidic it is. It determines how easily a proton can be removed. So a low pKa means that the proton is easily removable and. stronger acid. If the pKa is higher then the proton is not easily removable and the acid is weaker.

AdilaAhmed3I

Dear Dr. Lavelle,
Thank you so much for all your help this quarter with chem 14A! All the resources and time you put into this class and into helping us was so useful and let me excel in chem! I’m looking forward to taking chem 14b with you and hopeful for a great winter quarter!!

AdilaAhmed3I

how would you figure out the answers for 6A 17 "6A.17 State whether the following oxides are acidic, basic, or amphoteric: (a) BaO; (b) SO3; (c) As2O3; (d) Bi2O3." what would the explanation be for each? So an easy way to look at it would be that nonmetal oxides (like SO3) are acidic, met...

AdilaAhmed3I

hello, how does one find a coordination number? The coordination number is the number of atoms bonded to the atom. So here are some steps to finding it: 1. Identify the central atom in the chemical formula and this is usually a transition metal 2. Locate the atom, molecule, or ion nearest the centr...

AdilaAhmed3I

I think of equatorial as the equator line on a globe. It goes horizontally like on the x plane.
Axial is like an axes on a globe. It goes vertically on the Y plane.

AdilaAhmed3I

So an easy way to determine polarity is by seeing is the molecule is "balanced" or "lopsided". If it is a molecule like CCl4 where all the atoms surrounding the C are Cl, it is balanced and nonpolar. This is because the electronegativity between the Cl and C (the Cl-C bond) are t...

AdilaAhmed3I

The way I learned how to look at it was first to look at the 3D diagrams for all the basic shapes (tetrahedral, octahedral, etc). Once you see these, you can have a basic idea of where atoms will go and that can be used for all the variations like bent or trigonal pyramidal. Having the mental pictur...

AdilaAhmed3I

I use the textbook for textbook problems mostly. I learn better when someone is explaining it rather than reading, so if I get stuck, I'll watch a youtube video on it to clarify.

AdilaAhmed3I

Being close to purple might be safer since they have not been acting suspicious throughout the game but I would still be wary.

AdilaAhmed3I

Before COVID, I would usually go to a coffee shop or something similar to study but with COVID, I've had to adjust that. I usually do my work at night because no one's awake so it's quiet and no one comes into my room. I will study for a certain amount of time or do a certain amount of homework and ...

AdilaAhmed3I

Delocalized pi bonds can occur in resonance structures. A bond pair can seem to move between two different pairs of atoms which can be seen in the different resonance structures. They are considered delocalized because the pi bond found in the double bond is shared among the bonds and does not belon...

AdilaAhmed3I

How do Mr. and Mrs. Claus introduce their son?

"This is Arsenic"

(arsenic - our son Nick)

AdilaAhmed3I

I think this midterm was definitely a bit harder just because of the concepts required for it. There is more conceptual questions that can be asked and lewis structures are really easy to mess up. I was for sure more worried for this midterm than I was for the first one but at this point, I am just ...

AdilaAhmed3I

Does anyone know how to calm down your anxieties before you take this final? Since having test anxiety can be very distracting while you're trying to study or even while you're taking the test itself. Open to any tips:) Honestly, one thing that might cause you more anxiety is if you keep trying to ...

AdilaAhmed3I

Can anybody help explain to me why sigma bonds allow so much more flexibility than pi bonds? I still don't really understand how it allows the atoms to rotate Sigma bonds have "end to end" overlapping unlike pi bonds which have lateral overlap (where the sides overlap) single bond: https:...

AdilaAhmed3I

Why can there only be one sigma bond between two atoms? Why does a double bond have to be a sigma bond and pi bond and then a triple bond a sigma bond and two pi bonds? There can only be one sigma bond between two atoms because of the way they overlap. When the orbitals from two atoms overlap end-t...

AdilaAhmed3I

So cation are ions that lose electrons and have a positive charge. These would usually show up in group 1-13 and would have formulas like Ca+2. For these atoms, the quickest way to become stable (or like the noble gases) is to give up electrons and have an overall positive charge. For anions, these ...

AdilaAhmed3I

Hi! I was going over the homework for this section and I realized I don't really understand part b of this problem: Give the notation for the valence-shell configuration (including the outermost d-electrons) of (a) the alkali metals; (b) Group 15 elements; (c) Group 5 transition metals; (d) the “co...

AdilaAhmed3I

Hi everyone! I was wondering if you guys could help me on part (c) of this problem? I was a little confused by the answer because they used LDF when they compared the two molecules, and I was wondering why we wouldn't be able to use dipole-dipole in this situation? Problem 3F.5: Suggest, giving rea...

AdilaAhmed3I

I think that valence electrons are every electron after the noble gas, but do we include d electrons? In the textbook problems, it sometimes does and sometimes doesn't include the d electrons as the valence. For example, how many valence would Sb +3 have? It's electron configuration is 4d105s2, so ...

AdilaAhmed3I

Does [N3]- or HNNH have a longer bond length? For N2H2, there is one double bond and two single bonds. The single bonds are going to be longer than the double bond. For [N3]-, there are two double bonds, so they are going to be the same length. The bond lengths are going to be different between the...

AdilaAhmed3I

I think Lavelle said he would be reviewing questions that a lot of people missed on M1 and M2 for the final but I am unsure if he is going to be reviewing them now.

AdilaAhmed3I

We use formal charge to find the most stable lewis structure, but do we have to include all possible variations of the lewis structure (like we would with resonance)? Or can we just use the most stable structure? I think it depends on the question that is asked. Usually for formal charge questions,...

AdilaAhmed3I

I want to better my study habits for the final? What are some studying methods that have helped you guys? What do you try to avoid? I usually go through my notes first and see what I am weak at or need more clarification ( this is after I've watched all the lectures and modules). Once I find where ...

AdilaAhmed3I

I am not sure if anyone struggles with test anxiety... if you do, what are some techniques you guys use to deal and control test anxiety? Thank you. I try to calm my self first by just breathing because I find that they first thing that happens to me is that my breathing starts becoming weird and t...

AdilaAhmed3I

I am having trouble figuring out what charges to assign to each atom. I calculated the formal charge for each atom using the formula, but I kept getting the wrong answer. I think I may be using the formula wrong, for the amount of valence electrons of the atom would that be the amount assigned in t...

AdilaAhmed3I

Why does oxygen have a lower first ionization energy than both nitrogen and fluorine? How do we determine reasons for ionization energy differences? For ionization energy we have to look at orbital diagrams. Let's look at the 2p sublevel for each element. Nitrogen has all half filled orbitals which...

AdilaAhmed3I

A good way to think about electron-electron repulsion is with magnets. If you put two magnets together with the same ends facing each other, they repel. So if you tried to put the two negative ends together, they push against that and you can't really push them together. The same thing is happening ...

AdilaAhmed3I

I usually relax by watching a drama or listening to music. Recently, I've been playing Among Us more so I use that to relax as well. If I have a lot of time, I like to read (but that hasn't been happening much with school).

AdilaAhmed3I

So for this problem you would need to find the molar mass of Cl2 which is about 71 grams and then convert to kg which would be .071 kg. Once you convert from g to kg, you then need to convert to kg/molecule rather than keeping it in kg/mol. You would divide by Avogadro's number. This will put it in ...

AdilaAhmed3I

If you are given the quantum numbers for n, l, and m sub l, how would you go about finding the number of electrons in the atom? For example: n=7, l=2, m sub l=-1 For quantum numbers, I think you can use them to find the maximum number of electrons. Lets use the numbers 2, 1, 0, +1/2 First you would...

AdilaAhmed3I

Personally, I liked the audio visual modules more than the lectures because I could understand them a little better. The lectures were good but the audio visual ones just helped me a little more.

AdilaAhmed3I

I usually look through my notes first and see where my weak points are and maybe watch some videos on youtube as a supplement to give me more information. You could also read the textbook but I find that the textbook sometimes gives too much information and might be confusing. Then I would do practi...

AdilaAhmed3I

Samin Kabir wrote:Why do we have to include the delta sign above the arrow on only combustion rxns?

Combustion reactants are where the main reactant is supposed to be like burned so the symbol "Δ" is often used to indicate that the reaction is to be heated.

AdilaAhmed3I

Hello, When we have to balance chem equations do we have to include the states of matter in all components. Additionally how do we know what state of matter a reactant/product is in? I think Lavelle said that he would give us the states of matter of the reactants/products but I am not completely ce...

AdilaAhmed3I

Hi I'm still confused over the difference between electron affinity and electronegativity. Do they effectively go hand in hand? The electron affinity of an atom or molecule is defined as the amount of energy released when an electron is added to a neutral atom or molecule in the gaseous state to fo...

AdilaAhmed3I

How do you find the electron affinity in kJ/mol? So first, you would convert the incident wavelength into energy using E= hv/lambda equation. This would be in E/photon. Then you would convert the 0.137 eV into Energy by multiplying it by 1.602x10^-19 J and it would become energy in joules. Subtract...

AdilaAhmed3I

Hi! I was reading the textbook in Focus 1, and I saw that there was a ratio "e/m, the ratio of the magnitude of the electron’s charge e to its mass m." I am overall just really confused on the concept because of the values of e=1.602×10^−19 C and m=9.109×10^−31 kg. Can someone please expl...

AdilaAhmed3I

When multiplying two numbers in scientific notation, multiply their coefficients and add their exponents. When dividing two numbers in scientific notation, divide their coefficients and subtract their exponents. If you remember from math where we were taught how to multiply and divide with exponents...

AdilaAhmed3I

You would use the mass of an electron which is approximately 9.1093837015 x 10^-31 kg.

AdilaAhmed3I

If you know the frequency of the UV radiation, you can use the equation E = hv, h being Planck's Constant 6.626 x 10^-34 Js. If all you know is the wavelength, you can use the equation frequency = (3.00 x 10^8) / wavelength, then use the energy equation above with the calculated frequency. Hope thi...

AdilaAhmed3I

Usually in chemistry ( or at least that I have seen), we mainly focus on infrared, ultraviolet, and visible light. You can tell them apart by their wavelengths. Infrared light has the longest wavelengths of the three (700 nm to 1 mm), then visible lights (390 nm to 700 nm), and finally, ultraviolet ...

AdilaAhmed3I

replying to Vanessa:

No they are not. For the .987x10^-4, it should not be written this way because proper scientific notation would be 9.87x10^-5 because you have to move the decimal point over to the right by one so it would not be the same as 9.87x10^-3.

.987x10^-4 = .0000987

9.87x10^-3 = .00987

AdilaAhmed3I

So first I like to get all the information I need. When doing empirical formulas, you need the amount of the elements in the oxide which would be the tin and the oxygen. So you know that you have 1.50 g of tin which we can convert to grams using molar mass. To find the oxygen, we would have to subtr...

AdilaAhmed3I

When doing these problems, instead of looking for the reactant in excess, try looking for the limiting reactant and the other one will be the one in excess. I find this to be an easier way of thinking about the problem.

AdilaAhmed3I

First we are going to use the E= (planck's constant x speed of light) / wavelength. You need to convert the wavelength from nm to m in order to use it. Using this formula, you should get energy per photon. Then once you get energy per photon, you are going to divide the total energy (11J) by the ene...

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