CHEMISTRY COMMUNITY

Isabella Nassir 2B

I understand how to to calculate bond enthalpy with the given values, but how come the answer is a negative bond enthalpy in the answer key? I do not understand how they solved this problem in the key with all the different reactions, can someone please explain this method? How is it different from ...

Isabella Nassir 2B

Yes we use Pt (s) or other conducting solids like Cu(s) in the cell diagram when there is no other metal conducting solid. the order is anode| salt bridge |cathode with || symbolizing the salt bridge.

Isabella Nassir 2B

Hi,
The way I understood this concept was that because kinetic control comes from a fast reaction, the rate of reaction is already fast and able to overcome lower activation energy barrier without the need of a high temperature. So, therefore, kinetic control may occur with a low temp

Isabella Nassir 2B

If by hydrates, you mean adding water molecules H2O(l) to the reactant to get the (aq) products then yes, but they are excluded from the ICE table because they are liquids. If you mean hydrates in other ways, I am not sure but I do not believe so as I don't have much recollection of it being heavil...

Isabella Nassir 2B

Even though I'm not entirely sure how to write the equation shown in the solution manual for this problem, I used the fact that Al was a salt with Cl3 to assume that it must be acting as a acid and thus used the Ka for Al, 1.4x0^-5 and set it equal to x^2/0.055-x. From here, I changed 0.055-x to si...

Isabella Nassir 2B

How do we solve question number 6D.15 b? I am not sure how to write the reaction for AlCl3 weak acid?

Isabella Nassir 2B

For the Chem 14b course, are we expected to know how to use hydrates in reactions to solve for pH?

Isabella Nassir 2B

505771920 wrote:I think you would have to also have the Ka whether it be given or you have to look it up

The problem did not provide Ka, however it is provide other molarities of different acids

Isabella Nassir 2B

How can you calculate the pH of CH3NH3Cl with just 0.20 M given?

Isabella Nassir 2B

In question 7.17 in the textbook, part e, why does a catalyst not affect the overall rate of reaction?

Isabella Nassir 2B

Why does increase temperature , increase rate constant of higher Ea? I thought rate constant stays constant?

Isabella Nassir 2B

The order of B is second order. we can solve this by looking at the data by looking at reactions 2 and 3. concentration of B increases by a ratio of (3.02/1.25), and initial reaction rates increase by (3.02/1.25) squared... this is how we know the order of B is second order.

Isabella Nassir 2B

505766240 wrote:I think it's because the data is in mmol per L, so you would have to change it to mol per L.

But I thought you could keep all the variables in mmol/L if initial rate and concentrations are all in mmols? Why is it different here

Isabella Nassir 2B

Does anyone know if textbook problem 7A.17 is an error in the solution manual? I cant figure out why I am getting it wrong and cannot find it in the error manual.

Isabella Nassir 2B

When multiplying molarities of reactants together to find the rate constant k, like in homework question 7A.17, why are the molarities multiplied by 10^-3? If someone knows why they did that in the answer manual please let me know. Thank you!

Isabella Nassir 2B

where can I find the error solutions guide manual for the questions that are answered wrong?

Isabella Nassir 2B

We need Pt (s) whenever there is no solid metal present in the cathode or anode or both.

Isabella Nassir 2B

Who are the lucky winners?! :)

Isabella Nassir 2B

Julia Zahra wrote:its the amount of energy available to do work

What is the difference between GFE and Activation Energy?

Isabella Nassir 2B

Thank you so much for sharing! As someone who is thinking about med school, this advice is really helpful.

Isabella Nassir 2B

azurexrose wrote:I just had boba!! Is there a chemical reason why sometimes the boba pearls are hard and sometimes they are softer?

Sometimes if the tapioca pearls get too cold or come into direct contact with the ice before other liquid has been added, they can start to harden.

Isabella Nassir 2B

I've always found this interesting as well! I think this is why there's an area of study called food science, because really, cooking/baking is a bunch of chemical reactions! How fun! I completely agree and i think the most interesting part is that the ratios whole baking / cooking are so important...

Isabella Nassir 2B

Speaking of culinary chemistry, if anyone has any recipes that can be made with ~microwave~ radiation let me know. Dorm life is a struggle. Trader Joe's has a lot of really nice and delicious frozen food. I really like their potstickers and butter chicken, but they have a lot of variety. I also rec...

Isabella Nassir 2B

I am confused as to what Gibbs Free Energy is. What does it do? What is it? I would appreciate if someone could explain this please.

Isabella Nassir 2B

Glad that helped. Please assist in communicating to students that 100s of questions are being repeated even after I have answered them and sent the links to everyone so that they are aware of my answers. Yes, will do! I usually have many questions regarding the homework, so this is very helpful to ...

Isabella Nassir 2B

One of the most recognizable corrosion reactions is the rusting of iron. Rust is caused by iron reacting with oxygen gas in the presence of water to create an oxide layer. Iron can form several different oxides, each having its own unique color. Red rust is caused by the formation of iron(III) oxide...

Isabella Nassir 2B

Both arrows pointing down means Delta G is decreasing (negative) and therefore those arrows represent spontaneous changes. In the labels below: Progress of the reaction in the forward direction is R ---> P and therefore Q < K. Progress of the reaction in the reverse direction is P ---> R and theref...

Isabella Nassir 2B

I am having trouble writing short hand notation equations for the galvanic cell problem in the achieve homework q7. How to we determine which substance goes where when there are three slots on both sides?

Isabella Nassir 2B

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)⟶ClO−2(aq)+O2(g) I was able to define the oxidizing and reduci...

Isabella Nassir 2B

When Germany invaded Denmark in World War II, the Hungarian chemist George de Hevesy dissolved the gold Nobel Prizes of Max von Laue and James Franck in aqua regia to prevent the Nazis from stealing them. He placed the jar with the solution on a shelf in his laboratory and, after the war, precipitat...

Isabella Nassir 2B

The diagram shows the free energy change of the reaction A(g)+B(g)↽−−⇀C(g) The reaction progress starts on the left with pure reactants, A and B, each at 1 atm, and moves to pure product, C, also at 1 atm, on the right. Identify whether the reaction is spontaneous or nonspontaneous in the forward a...

Isabella Nassir 2B

The diagram shows the free energy change of the reaction A(g)+B(g)↽−−⇀C(g) The reaction progress starts on the left with pure reactants, A and B, each at 1 atm, and moves to pure product, C, also at 1 atm, on the right. Identify whether the reaction is spontaneous or nonspontaneous in the forward an...

Isabella Nassir 2B

For a gaseous reaction, standard conditions are 298 K and a partial pressure of 1 bar for all species. For the reaction 2NO(g)+O2(g)↽−−⇀2NO2(g) the standard change in Gibbs free energy is ΔG∘=−69.0 kJ/mol. What is ΔG for this reaction at 298 K when the partial pressures are PNO=0.400 bar, PO2=0.500 ...

Isabella Nassir 2B

Calculate the standard change in Gibbs free energy for the reaction at 25 °C. Refer to the ΔG°f values.

6Cl2(g)+2Fe2O3(s)⟶4FeCl3(s)+3O2(g)

Isabella Nassir 2B

The ΔHvap of a certain compound is 37.87 kJ·mol−1 and its ΔSvap is 87.40 J·mol−1·K−1.

What is the boiling point of this compound?

Isabella Nassir 2B

4.29 Crude petroleum is often contaminated by poisonous hydrogen sulfide gas. The Claus process for the extraction of sulfur from petroleum has two steps: (b) What enthalpy change would be associated with the production of 60.0 kg of sulfur? (2 MOL SULFUR) c) Would the reactor need to be cooled or h...

Isabella Nassir 2B

4E.9 Benzene is more stable and less reactive than would be predicted from its Kekulé structures. Use the data in Table 4E.3 to calculate the lowering in molar energy when resonance is allowed between the Kekulé structures of benzene.

Isabella Nassir 2B

Hi, I am really confused on the method in which we are supposed to use in order to calculate total reaction enthalpy with bonds. How do we know which bonds to use? ex
4E.5 Use the bond enthalpies in Tables 4E.2 and 4E.3 to estimate the reaction enthalpy for
a) 3C2H2 ---> C6H6

Isabella Nassir 2B

A hot lump of 37.4 g of copper at an initial temperature of 54.0 °C is placed in 50.0 mL H2O initially at 25.0 °C and allowed to reach thermal equilibrium. What is the final temperature of the copper and water, given that the specific heat of copper is 0.385 J/(g·°C)? Assume no heat is lost to surro...

Isabella Nassir 2B

If you combine 350.0 mL of water at 25.00 ∘C and 100.0 mL of water at 95.00 ∘C, what is the final temperature of the mixture? Use 1.00 g/mL as the density of water.

Isabella Nassir 2B

Carbon disulfide can be prepared from coke (an impure form of carbon) and elemental sulfur.

4C(s)+S8(s)⟶4CS2(l)ΔH∘=+358.8 kJ

Calculate the amount of CS2 produced when 373 kJ of heat is absorbed.

Isabella Nassir 2B

I keep having trouble with this question. First, I converted pH to pOH and then turned it into [OH-]. but then I seem to get confused about the steps and calculations afterward. Where do I go after this? Question: The Kb for an amine is 4.480×10−5. What percentage of the amine is protonated if the p...

Isabella Nassir 2B

NH3 is a weak base ( Kb=1.8×10−5 ) and so the salt NH4Cl acts as a weak acid. What is the pH of a solution that is 0.022 M in NH4Cl at 25 °C?

Isabella Nassir 2B

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 0.028 M in NaClO at 25 °C?

Isabella Nassir 2B

Consider the reaction of NH3 and I2 to give N2 and HI. 2NH3(g)+3I2(g)↽−−⇀N2(g)+6HI(g) Using two or more of the given equations, determine the equilibrium constant, K , for the reaction of NH3 with I2. H2(g)+I2(g)↽−−⇀2HI(g)I2(g)↽−−⇀2I(g)N2(g)+3H2(g)↽−−⇀2NH3(g)H2(g)+Cl2(g)↽−−⇀2HCl(g) Ka=160 Kb=2.1×10−...

Isabella Nassir 2B

At equilibrium, the concentrations in this system were found to be [N2]=[O2]=0.100 M and [NO]=0.500 M. N2(g)+O2(g)↽−−⇀2NO(g) If more NO is added, bringing its concentration to 0.800 M, what will the final concentration of NO be after equilibrium is re‑established? [NO]final= M I do not understand ho...

Isabella Nassir 2B

15. At a certain temperature K = 4.0 for the esterification of ethanol and acetic acid: C2H5OH (aq) + CH3COOH (aq) ⇌ CH3COOC2H5 (aq) + H2O (l) If initially 2.0 moles of C2H5OH and 1.0 mole of CH3COOH are in a 1.0 L aqueous solution, what are the equilibrium concentrations of the organic molecules. f...

Isabella Nassir 2B

At a certain temperature, the given reaction has an equilibrium constant of Kp=415 .

PCl3(g)+Cl2(g)↽−−⇀PCl5(g)

PCl5 is placed in a sealed container at an initial pressure of 0.0340 bar . What is the total pressure at equilibrium?

Isabella Nassir 2B

What is the name for [Cr(NH3)3(OH2)3]3+ ?

is it triaquatriamminechromate (III)?

Isabella Nassir 2B

when writing the formula of a coordiation compound, do we pay attention to overall charge of the compound?

Isabella Nassir 2B

Why is angle b in peroxyacetylnitrate estimated to be 109.5 degrees and not 180 degrees (according to the textbook answers)? Isn't this bond orientation linear?

Isabella Nassir 2B

Noting that the bond angle of an sp3 hybridized atom is 109.5° and that of an sp2 hybridized atom is 120°, do you expect the bond angle between two hybrid orbitals to increase or decrease as the s-character of the hybrids is increased? can someone please explain the answer to this? I am a bit confus...

Isabella Nassir 2B

How do we identify hybrid orbitals, specifcally used by the phosphorus atom in molecules like PCl4?

Isabella Nassir 2B

Why are there two pi bonds and one sigma bond in a triple bond? It makes more sense to me that there would be 1 sigma and 1 pi but I know that is not correct.

Isabella Nassir 2B

How do we find the hybridization of Be in BeCl2?

Isabella Nassir 2B

I can't seem to find the questions with decimals. for example in 2F: 1, 3, 5, 7, 9, 13, 15, 12
2.27, 2.45, 2.57, 2.59, 2.61, 2.63. Where do I find these questions in the textbook?

Isabella Nassir 2B

What is the significance of the coordination number and how do we find it?
ex. Q 9C10 from the textbook.

Isabella Nassir 2B

How do we identify a chelating complex? for example between the isomers of diaminobenzene, which ones are chelating complexes?

Isabella Nassir 2B

is oxalate a polydentate ligand and if so how many binding sites does it have?

Isabella Nassir 2B

How do we find the maximum number of places on the ligand that can bind simultaneously to a single metal center?

Isabella Nassir 2B

What are the steps to identifying whether a ligand is a polydentate?

Isabella Nassir 2B

In textbook q 9C1, how do we identify oxidation number of the metal?

Isabella Nassir 2B

Why is it that lewis and bronsted acid and bases are different in terms of which accepts and donates?

Isabella Nassir 2B

Hi! I think if Cl are on the same side, the molecule will be polar. If Cl are on the opposite sides, the molecule will be non-polar since the dipole moments have opposite directions and will cancel out each other. It is just like the trans- and cis- example Professor Lavelle mentioned in class. Do ...

Isabella Nassir 2B

HI, I am kind of confused on whether a molecule, like AlCl2H2, can be determined either polar or nonpolar based on where the hydrogens and chlorines are placed. If the chlorines are next to each other and the hydrogens are next to each other, will the molecule be more polar or nonpolar? Or does it n...

Isabella Nassir 2B

I was just reading about non-stove cooking and stumbled across a passage describing how marination not only imbibes food with extra flavor but also breaks down proteins in meat dishes - when the marinade contains an acidic element, as it usually does - essentially "cooking" it without req...

Isabella Nassir 2B

This doesn't really have anything to do with cooking, and I'm unsure if someone already mentioned this... but I was thinking back to when I was younger and watching my mom prepare food around the house. I remember she'd cut apples and let them soak in orange juice, so they don't brown as quickly. B...

Isabella Nassir 2B

I really love this thread of applying chemistry to the culinary world. As the holidays are coming quick, are there any recommended recipes any of you recommend which connect back to our class material by any chance? :)

Isabella Nassir 2B

I am currently in Chemistry 14A with Professor Lavelle and had my first pass today but it would not let me enroll because I do not meet the prerequisites which I do. I am currently in Chemistry 14A and have already taken Biology and General Chemistry. Maybe something is not in my transcripts? Or is...

Isabella Nassir 2B

HI,
I was wondering whether chem 14B will still have online recordings of the lectures in case we cannot be present for a lecture? Please let me know.

Thanks!

Isabella Nassir 2B

An organic compound that is distilled from wood has a molar mass of 32.04 g/mol. Its composition by mass is 37.5% carbon, 12.6% hydrogen, and 49.9% oxygen.
Draw the Lewis structure of this compound.

how do I solve this?

Isabella Nassir 2B

What is the difference between primarily ionic and more ionic character? Is there even a difference?

Isabella Nassir 2B

How do we find whether a compound is primarily ionic? if given a set of compounds.

Isabella Nassir 2B

For each pair, determine which compound has bonds with greater ionic character: (a) HCl or HI

Help please

Isabella Nassir 2B

What is the oxidation number of chlorine in the perchlorate ion? (whats the process)

Isabella Nassir 2B

Which of these three methods for determining the most plausible Lewis structure of the perchlorate ion is not consistent with the other two methods? Using oxidation number to determine the most plausible structure. Using bond length to determine the most plausible structure. None of the methods are ...

Isabella Nassir 2B

Achieve question 9 part 3:
Which of the Lewis structures of the perchlorate ion is most plausible based on the oxidation number? Assume that lone pairs belong to the atom to which they are attached but that all electrons shared in a bond belong to the more electronegative atom.

Isabella Nassir 2B

The chlorine–oxygen bond length in the perchlorate ion is found experimentally to be 144 pm for all four bonds. The average length of a Cl−O bond is 172 pm and the average length of a Cl=O bond is 140 pm . Which of the Lewis structures of the perchlorate ion are most plausible based on the experimen...

Isabella Nassir 2B

Go to quick links and then my post!

Isabella Nassir 2B

https://phys.org/news/2021-10-molecule- ... umors.html Found this super interesting. For all the people interested in medicine or cancer research: "New molecule targets, images and treats lung cancer tumors in mice"

Isabella Nassir 2B

https://www.sciencedaily.com/releases/2 ... 175142.htm "New material could pave the way for better, safer batteries" thought this was interesting!

Isabella Nassir 2B

I frequently come back to this post for advice. Thanks again for sharing it helps a lot to hear from someone with experience in the class and in a field many of us are interested in!

Isabella Nassir 2B

Wow, I feel so inspired by your story! thank you so much for sharing.

Isabella Nassir 2B

G.25 Practitioners of the branch of alternative medicine known as homeopathy claim that very dilute solutions of substances can have an effect. Is the claim plausible? To explore this question, suppose that you prepare a solution of a supposedly active substance, X, with a molar concentration of . T...

Isabella Nassir 2B

You use an electron microscope in which the matter wave associated with the electron beam has a wavelength of 0.0187 nm. What is the kinetic energy of an electron in the beam, expressed in electron volts?

Isabella Nassir 2B

The electron affinity of thulium has been measured by a technique known as laser photodetachment electron spectroscopy. In this technique, a gaseous beam of the anions of an element is bombarded with photons from a laser. Electrons from the anion are then ejected and their energies are detected. The...

Isabella Nassir 2B

What would the speed of each particle be if it had the same wavelength as a photon of red light (lamda=750.0 nm)?
proton (mass=1.673×10−24 g) speed:

I dont know why I keep getting a wrong answer. Can somebody explain step by step please?

Isabella Nassir 2B

I need help with this question about how to solve for max wavelength with the work function.. As you may well know, placing metal objects inside a microwave oven can generate sparks. Two of your friends are arguing over the cause of the sparking, with one stating that the microwaves "herd"...

Isabella Nassir 2B

Please help! I do not understand how we find the answer to this question:

Calculate the uncertainty (indeterminacy) in position of an electron if its uncertainty in speed is one hundredth the speed of light.

Thanks!!

Isabella Nassir 2B

How do we solve for the number of electrons?
"What is the maximum number of electrons that could be ejected from this metal by a burst of photons (at some other frequency) with a total energy of 6.92×10−7 J?
number of electrons:"

Isabella Nassir 2B

Thank you so much for this post. I am very interested in medicine and having personal advice from a med student is so inspiring and important to me.

Isabella Nassir 2B

I came across this problem in the homework and I am having trouble trying to figure it out.

When a metal was exposed to photons at a frequency of 1.22×1015 s−1, electrons were emitted with a maximum kinetic energy of 3.40×10−19 J.
Calculate the work function, Φ, of this metal.
Φ =
J/photon

Isabella Nassir 2B

Achieve question number 5
"How many photons with a wavelength of 823 nm are needed to melt 435 g of ice? The enthalpy of fusion of water can be found in this table."

Isabella Nassir 2B

I am having trouble finding the number of photons required for absorption. Is there a specific equation which solves for this? Specifically for question number 4 in the achieve homework. "A liquid is exposed to infrared radiation with a wavelength of 4.86×10−4 cm. Assume that all the radiation ...

Isabella Nassir 2B

Yes, the zeros after the decimal place are considered trailing zeroes and they do count as sig figs.

Isabella Nassir 2B

What is a quick method to memorizing unit conversions?

Isabella Nassir 2B

Hi, I do not understand this question and I am really lost. I pasted the question below. "Consider the nucleophilic addition reaction of 2‑butanone with excess propyl magnesiumbromide, made in situ by reacting 1‑bromopropane with metallic magnesium, to make 3‑methyl‑3‑hexanol. Reaction scheme w...

Isabella Nassir 2B

I was having trouble with this question from the week 1 homework (Q10) "Caproic acid has the odor of goats. (In fact, Capra is the genus of the domestic goat.) The compound contains only C, H, and O and was experimentally found to have a molar mass of 110±10 g/mol . When a 1.000 g sample of cap...

Isabella Nassir 2B

Net number of moles is found by adding up total reactant moles and total product moles and find the difference between them.

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