CHEMISTRY COMMUNITY

luludaly2B

Could someone walk me through how to solve this? Thanks!

luludaly2B

Can someone walk me through this problem? Thanks!
A certain reaction has an activation energy of 47.54 kJ/mol. At what Kelvin temperature will the reaction proceed 5.00 times faster than it did at 301 K?

luludaly2B

Could someone help me with this problem? Thanks!

A particular reactant decomposes with a half‑life of 167 s when its initial concentration is 0.276 M. The same reactant decomposes with a half‑life of 205 s when its initial concentration is 0.225 M.
Determine the reaction order.

luludaly2B

Could someone help me with this problem? I'm not really sure where to start. Thanks!

Dinitrogen pentoxide, N2O5, decomposes by first‑order kinetics with a rate constant of 3.7×10−5 s−1 at 298 K.
What is the half‑life, in hours, of N2O5 at 298 K?

luludaly2B

Could someone help me with this question? Thanks!

The rate constant for this zero‑order reaction is 0.0330 M·s−1 at 300 ∘C.
A⟶products

How long (in seconds) would it take for the concentration of A to decrease from 0.950 M to 0.220 M?

luludaly2B

Could someone help me with this problem? Is it correct to say that the zero order would be 1/s, because those are the units for k? If so, where do I go from there? Thanks!

luludaly2B

Hi! I am having trouble with this problem and I'm not sure what I'm doing wrong. I found the rate of change for A by doing 0.15-0.640 divided by 402. Then I multiplied this number by -2 in order to find the rate for B. Why is this wrong? Thanks!

luludaly2B

Could someone walk me through how to do this problem? Thanks! I know E knot is going to be 0, but I keep getting the wrong answer when I plug in the numbers for the nernst equation. What would the potential of a standard hydrogen electrode (S.H.E.) be under the given conditions? [H+]=0.21 M P H2 =2....

luludaly2B

Now I am just having trouble balancing the N₂H₄ -> NO equation. For the first half-reaction, I got
ClO₃^-+3H₂O+6e^-->Cl^-+6OH^-. Is this correct?

luludaly2B

Can someone help me balance this equation? I keep getting the wrong answer. I know that ClO − 3 is the oxidizing agent while N 2 H 4 is the reducing agent, however I can't seem to balance the half equations correctly. Thanks! The problem reads: Identify the oxidizing and reducing agents in the skele...

luludaly2B

I think it's a lot easier to balance each half-reaction individually and then add them together. Essentially, you would need to balance the half-reaction involving Au and the half-reaction involving HNO 3 ; then, you would add them together and factor in the reactions with chlorine as well. I am ha...

luludaly2B

Hi, I am having a lot of trouble with this problem. It reads: For a particular redox reaction, ClO−2 is oxidized to ClO−4 and Cu2+ is reduced to Cu+ . Complete and balance the equation for this reaction in basic solution. The phases are optional. I am having trouble with figuring out the half-reacti...

luludaly2B

Can someone help me with this problem? Thanks!

luludaly2B

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

luludaly2B

Can someone help me with this problem? It reads: A galvanic (voltaic) cell consists of an electrode composed of magnesium in a 1.0 M magnesium ion solution and another electrode composed of silver in a 1.0 M silver ion solution, connected by a salt bridge. Calculate the standard potential for this c...

luludaly2B

Can someone help me with this problem? It reads: 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...

luludaly2B

The question reads:
For a particular redox reaction, ClO−2 is oxidized to ClO−4 and Cu2+ is reduced to Cu+ . Complete and balance the equation for this reaction in basic solution. The phases are optional.

Could someone help me out and explain why my answer is incorrect? Thanks!

luludaly2B

Hey guys! Im having some trouble with number 18 on the hw. Calculate the equilibrium constant, K , at 25.0°C for each of the reactions. Use the thermodynamic information provided in the table. The hydrogenation of acetylene to ethane. C2H2(g)+2H2(g)↽−−⇀C2H6(g) So far I've calculated the Gibbs Free ...

luludaly2B

Could someone help me with this problem? I'm not really sure where to start. Thanks!

luludaly2B

Yes, you are correct that for fusion and vaporization, both the change in enthalpy and the change in entropy are positive. The same is true for sublimation (solid to gas) since it is simply the sum of fusion and vaporization. For the opposite processes, both the change in enthalpy and the change in...

luludaly2B

The question asks: Based on the calculated ΔSvap values, arrange the liquid samples in order from most ordered to least ordered.
What does ordered mean in this context, and how can you tell based on the ΔSvap value? Thanks!

luludaly2B

I am having a little trouble understanding this concept. Could someone explain this question to me? It reads: Classify the phase changes by the signs of the system's ΔH and ΔS. Screen Shot 2021-02-14 at 3.09.39 PM.png I'm pretty sure when liquid goes to gas and solid goes to liquid, both ΔH and ΔS a...

luludaly2B

A 0.565 mol sample of NO2(g), initially at 298 K and 1.00 atm, is held at constant pressure while enough heat is applied to raise the temperature of the gas by 18.9 K. Calculate the amount of heat q required to bring about this temperature change, and find the corresponding total change in the inter...

luludaly2B

Earl Garrovillo 2L wrote:I used the PV=nRT equation, substituting the P, T, and V with the initial conditions of the problem

Thanks! This was super helpful. However, which gas constant should I use? The one that uses J or atm? Thanks!

luludaly2B

A sample of an ideal gas in a cylinder of volume 3.19 L at 298 K and 2.28 atm expands to 8.92 L by two different pathways. Path A is an isothermal, reversible expansion. Path B has two steps. In the first step, the gas is cooled at constant volume to 1.38 atm . In the second step, the gas is heated ...

luludaly2B

I understand why the first option is correct, as moles increase from 4 to 5, but why is the 3 option correct, as it goes from 3 moles to 3 moles? Thanks!

luludaly2B

I actually figured out this problem by remembering that grams can be roughly calculated as 1 g/ml, however I am confused as to why I don't need to include delta H_fus in this equation, unlike previous sapling problems. Could someone explain to me when delta H_fus is necessary? Thanks!

luludaly2B

The question reads: A hot lump of 47.7 g of aluminum at an initial temperature of 85.3 °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 aluminum and water, given that the specific heat of aluminum is 0.903 J/(g·°C)? Assum...

luludaly2B

The energy heat lost gained by the ice cube is equal to to the the energy lost by the surrounding water. The ice cube requires 6.01x10^3 j/mol to change from ice to water, so for 42.6 g of water, using the molar mass of water you can find the energy required to change all the ice to water. Once the...

luludaly2B

Could someone walk me through how to solve this problem? I'm not really sure where to start. Thanks!
If you combine 250.0 mL of water at 25.00 ∘C and 110.0 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.

luludaly2B

Hi, so for this problem we would use the given bond lengths to compare the amounts of energy absorbed in the reactants and released in the products of each reaction. So for the first reaction A + BC --> AB + C, we would compare the strengths of the B-C bond and the A-B bond. Because the A-B bond is...

luludaly2B

Could someone walk me through their process of solving this problem? It reads: An ice cube with a mass of 52.6 g at 0.0 ∘C is added to a glass containing 437 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⋅∘...

luludaly2B

Could someone help me with this problem?
The problem says: For each reaction, identify another quantity that is equal to ΔH∘rxn.

luludaly2B

Could someone help me with this problem? The problem states:
Based on relative bond strengths, classify these reactions as endothermic (energy absorbed) or exothermic (energy released).
I'm unsure where to begin. Thanks!

luludaly2B

Hey, I think you have the wrong equation to begin with. You should redo you ICE table and then manipulate your equation so that it is a quadratic equation: 0.032x^2+x-0.154. In the end your percentage has to be small so you would ignore the negative x value. You take that value and divide it by 0.1...

luludaly2B

I'm not sure if that equation is correct, but the way I did it was I got the equation (0.154-x)/x^2 = 0.0032. Then, I rearranged the equation so that it becomes a quadratic. It should look like this: 0.032x^2+x-0.154. Then, you just use the quadratic to get the x value. And you must use the most re...

luludaly2B

The way I think about it, if the pKa is smaller than the pH, then the acid in question can contribute to making the solution more acidic, so the species in which the H+ is lost is the predominant species. if the pKa is larger than pH, then the acid likely will not contribute to making the solution ...

luludaly2B

What helps me is that I think of p as -log₁₀(H). Therefore, to find H+, you would isolate the H+ by multiplying both sides by negative 1, putting 10 to the negative pH power. Hope this helps!

luludaly2B

The question is: The Kb for an amine is 9.721×10−5. What percentage of the amine is protonated if the pH of a solution of the amine is 9.293 ? Assume that all OH− came from the reaction of B with H2O. I have solved for x by calculating pOH, then from there setting that equal to -log(x), finding that...

luludaly2B

The question is: The Ka of a monoprotic weak acid is 0.00891. What is the percent ionization of a 0.142 M solution of this acid? Could someone walk me through this? My equation is 0.00126522-0.00891x=x 2 . Is that right? When I plug that in a calculator there is not an x-intercept, so I don't know w...

luludaly2B

When solving after you have found expressions with x, I would take the square root of the entire equation first, leaving you with 2(.3+x)=(.9-2x).
From there, simplify, x=0.075. If the question is asking for the final concentration of NO, then make sure to plug x back in to find .9-2(0.075)=0.75.

luludaly2B

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? Could someone help me with this sap...

luludaly2B

start with the equation Kp=P PCl5 /P PCl3 *P Cl2 . From here, you can plug in the given value for Kp and the numerator would be P PCl5 -x and the denominator x 2 . From there, you can set up a quadratic equation, calculating x, and then adding all of partial pressures together to get the total press...

luludaly2B

For this question, I found it helpful to write out the expressions for each chemical equation's K value (using the brackets and such). Then, you can see that you can get the desired K value by multiplying the K of the reciprocal of equation 1 by equation 3. What I did was similar, but not the quite...

luludaly2B

You need to use the 1st and 3rd equations because these equations can be manipulated to form the initial equation. You need to do 1 over the K of the first equation and raise it to the power of 3 since 3 of the inverse of first equation form one part of the initial equation. For the third equation,...

luludaly2B

I was also wondering, if one set of phrases "favored" vs. "shifts" is preferred? Or if one is a more proper expression? even though they mean the same thing. I'm not sure, but I think favored is probably prefered, because the use of "shifts" may be misleading, nothing ...

luludaly2B

Is there a difference between saying a chemical equations "favors the left/right" vs saying a reaction "shifts towards the left/right?" Are these two statements saying the same thing or the opposite?

luludaly2B

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.

luludaly2B

Can someone walk me through how they solved #29 in the second chemical equilibrium module? The question is: A researcher fills a 1.00 L reaction vessel with 1.84 x 10-4 mol of BrCl gas and heats it to 500 K. At equilibrium, only 18.3 % of the BrCl gas remains. Calculate the equilibrium constant, ass...

luludaly2B

Can someone explain why the answer is (a) i=products ii= products. The question is: State whether the equilibrium shifts towards products, reactants, or neither when the given change occurs. 2 HI(g) + Cl2(g) ⇌ 2 HCl(g) + I2(s) delta H° = -238.0 kJ.mol-1 i. The volume of the system is compressed. ii....

luludaly2B

Why would K[Cu(en)₂(CN)₂] end in cuprate (I) and not cuprate (II)?

luludaly2B

I'm having trouble figuring out the charge of nickel from the mini marshmallow worksheet, and it's different from the answer key. The formula is [Ni(NH₃)₂O₂]Br₂. Could someone help me out? Thanks!

luludaly2B

Is there a difference between naming ONO vs NO2? In one worksheet, we were asked to write the chemical formula for Pentaamminenitritonickel(III) and I wrote [NI(NH3)5(NO2)]2+. Is this correct as well, even though the answer key says ONO? Thanks

luludaly2B

I had the same question. I keep counting 7 for both. Here is an image: Screen Shot 2020-12-12 at 5.38.34 PM.png For A, there are 5 nitrogens each with one lone pair, and 2 carbons that can accept an H. For G, there are 2 nitrogens, 2 oxygens each with 2 lone pairs, and one carbon. What am I missing?

luludaly2B

In one of the review worksheets, the question asked to rank Be, B, C, N, O and F in order from least ionized to most ionized. The correct answer was B<Be<C<O<N<F. Can someone explain why this is correct. I thought that the general trend over the periodic table is that elements have higher ionization...

luludaly2B

I would just remember the basic rules as discussed in Lavelle's lecture! Start with the greek prefix (di-,tri-,tetra-, etc), then name the ligands in alphabetical order, then add the transition metal cation! If the whole coordination compound has a negative charge, then add -ate to the end. Hope thi...

luludaly2B

I had trouble with this one at first too! For a, the shape would be bent, because there are three areas of electron density, two sets of bonded electrons and one lone pair (AX 2 E). Therefore, the measurement between each area of electron density should be a little less than 120 degrees because, if ...

luludaly2B

When do you know when do use -ate at the end of the name of a compound. For example, [Co(CN)₅(OH₂)]^2- is auqa pentacyanocobaltate, while [Co(NH₃)₅(SO₄)]⁺ is penta aminesulfatocobalt. Thanks!

luludaly2B

Hi! I had this problem during my discussion section, and I'm wondering how you would know that [Co(CN)₅(OH₂)]^2- would be aqua pentacyanocobaltate(III). After first, I thought it was pentacyanohydrocobaltate (iii). Why is that incorrect? Thanks!

luludaly2B

Could someone help me figure out the coordination number of [Pt(en)Cl2] and explain why it is not 2? I thought that the number of bonds is equal to the coordination number. Is that not true in this case? Also, what does the en indicate? Thanks!

luludaly2B

Could someone explain why this shape would be linear? Also, is it common for Lewis structures to be written like this, where one lone pair of electrons is seperated (like the two electrons are not next to each other so it looks like they are in separate distributions if that makes sense)?

luludaly2B

I had this question too, as it has the same number of electrons and all carbons have 4 sets of bonded electrons and each hydrogen has one pair of bonded electrons. I am not sure why it is incorrect, because the charges of each molecule are also neutral.

luludaly2B

Could someone help me figure out which one of these structures for C3H4 would be favorable? Thanks!

luludaly2B

Can someone help me with this question on the sapling homework? I am still having trouble understanding what it means for a molecule/bond to be polar. I thought, because there are two molecules with the same electronegativity on either side of the central molecule, the bonds are nonpolar. Is that in...

luludaly2B

Could someone explain what I did wrong? I know that there are three regions of electron density and one lone pair. Wouldn't the smallest bond angle between the two sets of bonded electrons be less than 109.5?

luludaly2B

The seesaw shape appears when there are 4 bonds and one lone pair of electrons, making a more stable structure. I included this chart which helps me visualize each shape! Hope this helps!

luludaly2B

m_l refers to the orientation in space of the orbital, while m_s is the spin of the electron. M_s is always either +1/2 or -1/2, while m_l can be l, l-1, ..., -l.

luludaly2B

I had trouble with this at first too, and what I always remembered was that Acids Accept, and therefore Lewis bases give electrons. This means that Lewis Acids are usually positively charged, while Lewis bases are negatively charged. Hope this helps!

luludaly2B

I think the textbook answer is correct. At ground-level, the formula for Mn is [Ar]3d 5 4s 2 , and when subtracting four electrons, you get [Ar]3d 3 . As Eliana said, to determine the number of valence electrons, you compute how many electrons away the formula is from the last noble gas, which in th...

luludaly2B

https://www.youtube.com/watch?v=GnXSGR- ... =emb_title

I found this video super helpful! Hopes this helps!
Also this chart!

luludaly2B

I have a basic understanding of how to determine whether a molecule is polar or nonpolar, however I am struggling to understand the "exceptions." For example, BF3 is nonpolar because the the geometry of the molecule allows the charges to cancel out? When does this apply and why? Thanks!

luludaly2B

I'm pretty sure that the shielding, although it may be present, doesn't have a great effect on the atomic radius compared to adding a whole other shell of electrons, which leads me to believe that nitrogen has a smaller radius.

luludaly2B

sometime the geometry of a molecule can affect its polarity. BF3, though have a high electronegative difference, is not polar because its geometry cancels the polarity. Can you explain this more? Why does the geometry of BF3 allow the molecule to be polar? Why is this not true for H2O or SO 4 2- ? ...

luludaly2B

Is there an error with this problem, or am I missing something? This is an SO2 molecule, not H2S, right? Would the answer still be dipole-dipole or would it be London dispersion?

luludaly2B

To rank the following anions in order or decreasing polarizability: I-, Se2-, N3-, O2-, Br-, you would take into consideration both size and electronegativity, correct?
Would the correct order be: I-, Se2-, Br-, N3-, O2-?
Thanks!

luludaly2B

Can someone explain what I did wrong?
The question says:
Draw the Lewis structures of the polyatomic ions and assign formal charges.
How do I assign formal charges on sapling? Thanks!

luludaly2B

Hi,
How do you calculate the charge of an element and molecule? Is knowing the charge on a element just based on memorization? If so, do you have any tips for memorizing the charges of specific elements?

luludaly2B

No, it didn't ask anything about formal charge. All it said was to include lone pairs. Carbon doesn't include any lone pairs, correct?

luludaly2B

Can someone help me with this question? I thought I did it correctly and I can't seem to figure out what I did wrong. Thanks!

luludaly2B

Hi! I am kind of confused by the concept of coordinate covalent bonds. For example, in Lavelle's lecture, he showed that to stabilize BF₃, you can add another flourine atom. Would that change the bond to be BF₄? Why is this allowed/how is it possible?
Thanks!

luludaly2B

Arrange these ions according to ionic radius.
P^(3-)
Cl^(-)
Ca^(2+)
S^(2-)
K^(+)

Could someone explain this concept to me? Thanks!

luludaly2B

If you take into consideration Hund's rule, you will recognize that configurations (a) and (c) are both in an excited state. This is because electrons must fill every open orbital (which is not true for c), but electrons do not double up until every subshell has at least one electron occupying every...

luludaly2B

Can someone explain this to me? I am having trouble understanding when an element releases more/less energy vs. when the energy is stored. The question is: Arrange these elements according to electron affinity: On a scale from "most energy released by gaining an electron" to "Most ene...

luludaly2B

I am having trouble understanding the concept of orbitals in general. For question 21 on sapling for me, it asks: "How many electrons in an atom could have these sets of quantum numbers?" N=3 N=4, l=0 n=6, l=3, ml= -1 Would these just be found based on memorizing properties of orbitals or ...

luludaly2B

The E. coli bacterium is about 2.5 μm long. Suppose you want to study it using photons of that wavelength or electrons having that de Broglie wavelength. What is the energy of E photon of the photon? For this question, I got the correct answer, it was 8.0 x 10 -20 . However, I am having trouble with...

luludaly2B

An excited hydrogen atom emits light with a frequency of 1.14x10¹⁴ Hz to reach the energy level n =4. In what principle quantum level did the electron begin?
I tried using v=R ((1/n² - 1/16)) but I think I'm messing up somewhere.

luludaly2B

Thank you! I did this and then multiplied by 1000, in order to convert the number into J from kJ. Is this correct?

luludaly2B

In 1.0 sm a 60 W bulb emits 11 J of energy in the form of infrared radiation of wavelength 1850 nm. What is the energy per photon of light emitted? How many photons of infrared radiation does the lamp generate in 1.0s?
Where do I begin this problem? I think the 60 W is stumping me.

luludaly2B

Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x10 5 . The work function for sodium is 150.6 kJ/mol. How much energy is required to remove an electron from one sodium atom? In the previous problem, I solved for kinetic energy, which was 1.99 x 10 -19 J. Where shou...

luludaly2B

Can someone explain what the vacuum permittivity constant (ε₀) is? It was mentioned in the textbook and I'm not really sure where it comes from or what it means. Thanks!

luludaly2B

Could someone help walk me through Self test 1B.5B? The question is: The police are monitoring an automobile of mass 2.0t(1t=10 3 kg) speeding along a highway. They are certain of the location of the vehicle only to within 1 m. What is the minimum uncertainty in the speed of the vehicle? Can you use...

luludaly2B

I know this question wasn't assigned but could someone help walk me through this question? Neon lights glow with orange light and they also emit radiation of wavelength 865 nm. Calculate the energy change resulting from the emission of 1.00 mol of photons at this wavelength. I found the energy per p...

luludaly2B

Can someone help walk me through this question? The work function of zinc is 3.63 eV. What is the longest wavelength of electromagnetic radiation that could eject electrons from zinc? I converted 3.63 eV to Joules by multiplying it by 1.602x10 -19 , but I don't know what to do from there. I looked a...

luludaly2B

Could someone help walk me through this problem? It is a two part question, and I think I understand part A, but not part B. Question 33 (A) is: Molybdenum metal must absorb radiation with a minimum frequency of 1.09 x 1015 s-1 before it can emit an electron from its surface. Answer the following tw...

luludaly2B

I also had a trouble with this question too. Both of you use 2.501 x 10^-19, however you use them in different contexts, and label them differently. Is this number both the work function and the threshold energy? Are both of these methods correct?

luludaly2B

Would someone mind double checking my work? The solution isn't given in the textbook and I just want to make sure I did everything correctly and did not miss any steps :) The question is: Carbon dioxide can be removed from power plant exhaust gases by combining it with an aqueous slurry of calcium s...

luludaly2B

Thanks for the help everyone! I actually reworked the whole problem, as I made conversion errors at the very start that threw off the entire problem. My answers are similar with Gwendolyn Hill and Madilyn Schindler. I realized that I also did not properly take into consideration the molar ratios, re...

luludaly2B

The problem is: Suppose that 28 g of NO 2 and 18 g of water are allowed to react to produce nitric acid and nitrogen monoxide in the reaction 3NO 2 (g) + H 2 O(l) →2HNO 3 (aq) + 1 NO(g) If 22 g of nitric acid is produced in the reaction, what is the percentage yield? First I found the moles of NO 2 ...

luludaly2B

I did the self test question M.2B and I just want to make sure I completed it correctly, because there was no answer given. The question is: (a) What is the limiting reactant for the preparation of urea from ammonia in the reaction 2NH 3 (g)+CO 2 (g)→OC(NH 2 ) 2 (s)+H 2 O(l) when 14.5 kg of ammonia ...

luludaly2B

Technically this problem wasn't really assigned, but I was reading through the textbook and thought I would complete the self-test problems as well, just to get some extra practice. The question is: "Calculate the amount of Ca(OH)2 formula units in 1.00 kg of slaked lime (calcium hydroxide), wh...

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