CHEMISTRY COMMUNITY

Ellison Gonzales 1H

This question also specifies that it is a galvanic cell, so I was wondering if we are to treat this problem any differently or if there are any differences in the process compared to the other types of cells? Thanks!

Ellison Gonzales 1H

I was wondering if anyone knew where the KOH came from? I’m not sure if it’s a typo or if it has a purpose. I was also wondering where the solo Ni(s) came from in the cell diagram? Is it because it’s a solid metal and so it can be used as the electrode?

Ellison Gonzales 1H

For parts b and c, determining the reactants and products for each half reaction is based on the overall reaction. For instance, for part b: We find the half reactions for H+(aq) and OH-(aq) O2(g) + 4H+(aq) + 4 e- --> 2H2O(l) 4OH-(aq) --> O2(g) + 2H2O(l) + 4e- (I flipped this half-reaction because ...

Ellison Gonzales 1H

Hi! I’ve seen this value, 0.693, in the solutions of the textbook problems a few times and it’s not in the problem. I think i missed something but where does this value come from? Thanks!

Ellison Gonzales 1H

Here is an equation page from a step up that has almost all the equations in one place. Hope it helps!

Ellison Gonzales 1H

I keep seeing the value “0.693” in equations and i was wondering where that value was coming from?

Ellison Gonzales 1H

Christine Ma 3L wrote:
Ellison Gonzales 1H wrote:Will k always have the unit s^-1 or can it depend on the situation?

It depends on the situation! The unit for rate is usually 1/(a unit of time), which can be seconds, minutes, hours, or any other unit of time, so it does depend on the situation.

Great thank you so much!

Ellison Gonzales 1H

Will k always have the unit s^-1 or can it depend on the situation?

Ellison Gonzales 1H

Hi! I was a bit confused on the solution’s explanation B being second order. When I divide 3.02/1.25 i get 2.4 and for the rate i get 2.9 when i divide 50.8/17.4.... so I don’t understand how we get (3.02/1.25)^2. Any help with this would be appreciated, thanks!

Ellison Gonzales 1H

Thank you Shannon and Gwirnowski! This helped a bunch!

Ellison Gonzales 1H

Could someone explain where exactly the 6 moles come from? Thanks

Ellison Gonzales 1H

Hi, I know this is probably a simple question but I’m not sure why it still isn’t clicking for me. #8 asks for the oxidation half of th reaction and the oxidation half of the reaction and then gives this: Cl2+2Cs⟶2CsCl I am pretty sure Cl- is the oxidation half and Cs is the reduction half. I don’t ...

Ellison Gonzales 1H

Hi, could someone help me balance the reducing agent half of this reaction? This is the full equation they give: [Pb(OH)4]2−(aq)+ClO−(aq)⟶PbO2(s)+Cl−(aq)

I am struggling on balancing the [Pb(OH)4]^2- ——> PbO2 part
Thank you!

Ellison Gonzales 1H

Hi! This is Can Yilgor’s response to someone else for this question and it is SUPER helpful so I thought I would just attach what they said bc I can’t explain it as well as them lol. Oh but also, don’t forget your phases in your final answer! “ To begin, determine the oxidation numbers of each eleme...

Ellison Gonzales 1H

I think you may just be missing the liquid phase (l) for 5H2O

Ellison Gonzales 1H

Thank you, Can!! That helped SO much! I was wondering though, do we always assume the H2O we add is in liquid phase and the OH we add is in an aqueous phase?

Ellison Gonzales 1H

For the half reaction: H2O2 —> O2 , can you just add H^+ and 2 electrons to balance the equation? Sorry I know that maybe a simple question but I keep getting a mistake and I’m not sure if this may be my problem

Ellison Gonzales 1H

I am also stuck on this problem, the hint says to balance the half reactions but I am confused how to do that with compounds, how do you know what goes into each half reaction? You would first need to identify the things getting oxidized and reduced. From the problem I had, Au was being oxidized to...

Ellison Gonzales 1H

How do we solve for the oxidation number of Au in HAuCl 4 ? Also, how do we know the oxidation number of Cl is -1 when in problem one it was +7? I believe we know Cl is -1 when chlorine is in the form of the monoatomic chloride ion, so Cl− In HCl has an oxidation number that is equal to its charge,...

Ellison Gonzales 1H

How do you know to use the equation with Q instead of K based off the question? If the question is asking you to compare something to a K value, is that when we use this equation with the Q?

Ellison Gonzales 1H

Do Delta G and Delta naught have the same units? Or does it depend on the situation?

Ellison Gonzales 1H

A good tip I learned is that all state functions are written with capital letters! Hope that makes it a bit easier to remember which ones are considered state functions!

Ellison Gonzales 1H

More mass means that molecule is more complicated and therefore has more options for possible states, which leads to greater entropy

Ellison Gonzales 1H

I thought I saw the book say that there is more entropy the more complicated the molecule gets? Did I misread that or is that true?

Ellison Gonzales 1H

Thank you Ria and Kimiya! Both of your explanations help a lot!

Ellison Gonzales 1H

For some of the problems in 4H of the textbook, I see them mentioning the number of “fundamental particles” of an element/compound when determining which compound will have the greater standard molar entropy. I was wondering what does it mean when it mentions fundamental particles and what part does...

Ellison Gonzales 1H

Also it’s good to keep in mind that after you have isolated ln(K), you take the natural exponent of the numerical value you have on the other side of the equal sign before it becomes K.... example: e^#

Ellison Gonzales 1H

I had the same question when i came across this questions. One way i did make sense of it though was by realizing the units we needed to end with to get enthalpy of vaporization, and solve according to what I needed my final outcome to be.

Ellison Gonzales 1H

Does delta H=q only when work is done on a system? Or can it be when it doesn’t do expansion too?

Ellison Gonzales 1H

Also, when regarding Cp,m and Cv,m values, what is the difference between an “atom” and “linear molecules”?

Ellison Gonzales 1H

Is there a difference when a question says Cp,m/Cv,m or Cp/Cv? I saw the book used both when explaining this concept

Ellison Gonzales 1H

Do you use the same equation for all 3 when finding heat capacity, specific heat capacity, or molar heat capacity?

Ellison Gonzales 1H

Is the way you calculate the specific heat capacity of a calorimeter different from how you calculate specific heat capacity in general? Or does it always occurs with a calorimeter?

Ellison Gonzales 1H

Another good thing to note is that heat capacity is an extensive property, meaning it depends on the amount of substance. Specific heat capacity is an intensive property, meaning it does not change as the amount of matter changes.

Ellison Gonzales 1H

Heat capacity is the heat required to raise the temperature of an object by 1°C and specific heat capacity is the heat required to raise the temperature of ONE GRAM of the object by 1°C (the gram part is a bug distinction)

Ellison Gonzales 1H

It’s good to know that when it mentions an open beaker, pressure is constant and then you follow what Sondia mentioned above ^

Ellison Gonzales 1H

When the problem states the reaction is happening @25 degrees, is this an indicator it is a neutralization? I noticed a pattern in some problems but I’m not sure if it is true or accurate

Ellison Gonzales 1H

My understanding is to keep an eye out for sulfuric acid and when you come a cross it, know it requires a 2nd deprotonation

Ellison Gonzales 1H

Is the unit for partial pressure in the ideal gas law always bar? Or bar and atm?

Ellison Gonzales 1H

Will we ever be expected to perform a phase change calculation when using Hess’s law? Or do we not need to know how to do that?

Ellison Gonzales 1H

Could someone clarify how we check our “x” after using the 5 percent rule? Also, is the 5 percent rule a part of Le chatelier’s principle? Thanks

Ellison Gonzales 1H

My understanding is that this “standard state” is so the element is in the same phase change and therefore is more consistent, or else enthalpy of the phase change would have to be calculated.

Ellison Gonzales 1H

I have seen in the book and in step ups that we final the % ionization by doing ([H3O+]/[HA] initial)*100.... but as a solution for the sapling homework they said to solve it by doing ([H30+]/[sum of A- and HA])*100. I don’t understand why they want us to add these two concentrations in the denomina...

Ellison Gonzales 1H

Hi Ashley! My understanding is that percent ionization is essentially the number of electrons taken off/away because it’s the percent dissociation of an acid

Ellison Gonzales 1H

If a reaction is exothermic (negative) raising the temperature will tend to shift the reaction towards reactants, if the reaction is endothermic (positive) is shifting towards products to happen

Ellison Gonzales 1H

Are bar and atm both units used for pressure? I know now that they practically have a 1:1 ratio so it’s just a fact of like “labeling it correctly?

Ellison Gonzales 1H

Would inverse also be when in some problem solutions they make the products a -x and the reactants a +x in the “change” section of an ICE table? I thought it was almost always that products are positive and reactants are negative but I’ve seen it done both ways now

Ellison Gonzales 1H

Hi Talia! I read in one of the hints on the sapling homework that so long as you divide your moles by liters before you state your final answer, you should be good. So you can do it before you put the value in your chart or after you’ve done all the long math and are practically finished

Ellison Gonzales 1H

When doing the “change” part for the ICE tables, I’ve seen some solutions in the text book make the products be a -x and I think it’s because they’re using the reverse reaction? So I was wondering if anyone knew what was a good indication to use the reverse reaction when creating the ice tables

Ellison Gonzales 1H

If delta H is negative that means heat is being given off and heat is a product. Another note to make is as the temps get higher, the equilibrium constant goes down and favors reactants more

Ellison Gonzales 1H

I’m confused on how this situation presented in 5J of the book can be true if adding gases doesn’t change pressure which then doesn’t effect concentration: “Suppose that the ammonia synthesis reaction, reaction A, has reached equilibrium. Now suppose that more hydrogen gas is pumped in. According to...

Ellison Gonzales 1H

Could someone list what terms are used when talking about Q? I get a bit confused on which terms are used for K or Q

Ellison Gonzales 1H

Hi Lucy! My understanding is that if [P] is greater than [R], then that means products are added to the equilibrium mixture and so Q temporarily rises above K since products appear in the numerator. So I think Q would no longer be less than K. Section 5J in the book talks about this a bit, you may b...

Ellison Gonzales 1H

Hi! Does anyone know when Dr. Lavelle says the Sapling assignments are due midnight Sunday of the week is he referring to Sunday as the first day of the week? Like is the Week 1 Assignment due on 11:59pm on Jan 10th or 17th? Thanks in advance :) Hi! He usually specifies what week they’re due. Since...

Ellison Gonzales 1H

I am having a lot of trouble getting into Sapling. If I try to go through CCLE it says it is invalid and if I try to do it through the sapling website it tells me that I need to do it through CCLE. I need to access it asap and my access code is only arriving this week. Please help, I don't knowhow ...

Ellison Gonzales 1H

This is an example/explanation in the text book that I don’t fully understand and hoping to get some help on it :) “The C atom of CO2, the Lewis acid, accepts an electron pair from the O of a water moleculethe Lewis base, and a proton migrates from an H2O oxygen atom to a CO2 oxygen atom. The produc...

Ellison Gonzales 1H

The oxidation state of the transition metal is another term for its charge. To find the oxidation state of Ag in Ag and (NH3)2, we would need to know the charge of the entire coordination complex. For example, in [Ag(NH3)2]+, you would need to total the charges of the transition metal and its ligan...

Ellison Gonzales 1H

Do we draw the Lewis structure for this question to see which molecule accepts or donates electrons? Also, why do we pay more attention to the electron exchange here instead of a proton or hydronium ion exchange?

Ellison Gonzales 1H

The best thing to do is write out the electron configurations and see what is most favorable in creating a neutral molecule. Zn has an oxidation state of 2+ so it will bond with two OH- to create a neutral stable molecule. Zn(OH)2 => Zn2+(OH-OH-) Hi! I just want to understand this point you made a ...

Ellison Gonzales 1H

How do we know that zinc will bond to OH in the first place? Because it is a metal?

Ellison Gonzales 1H

This is helpful to know! Thank you, Sophia!

Ellison Gonzales 1H

Yes every bond and lone pair are a region of e- density. Even if you have two lone pairs on the same atom ( example :o: ), it would be considered to have two regions of electron density

Ellison Gonzales 1H

What is a pi orbital?

Ellison Gonzales 1H

Delocalized pi bonds can only exist in a resonance structure. Since pi bonds typically exist in double or triple bonds, that double/ triple bond is able to move around in a resonance structure, meaning the pi bond is moving with it too. Therefore, the electrons for the pi bond are never permanently ...

Ellison Gonzales 1H

How are we to know when to draw a possible structure using a ring structure? I ask this question because a hint for sapling #17 was to draw a 3 membered ring structure but I was wondering if there was any advice to know when to do so

Ellison Gonzales 1H

If you’re talking about the smallest bond angle when comparing the angles within one structure, I see the smallest angle as being the one between two bonding pairs. Since there is more e- repulsion between a lone pair and a bonding pair, that will cause the other angles without lone pairs to be smal...

Ellison Gonzales 1H

If sigma bonds are for single bonds and a double bond involves sigma and pi, does that mean we have to draw out the Lewis structure to figure out how many bonds that density has?

Ellison Gonzales 1H

Just to clarify, lone pair electrons have more repulsions so therefore that angle is wider, correct? In that case, we just have to know that concept? Or is there certain angle degree that is associated with lone pair repulsion? Hi! Yes you are correct, lone pair repulsion is greater than bonding pa...

Ellison Gonzales 1H

Just to clarify, lone pair electrons have more repulsions so therefore that angle is wider, correct? In that case, we just have to know that concept? Or is there certain angle degree that is associated with lone pair repulsion?

Ellison Gonzales 1H

Just something good to keep in mind is that coordinate covalent bonds are usually formed when dealing with acids and bases

Ellison Gonzales 1H

Thank you everyone this was super helpful!

Ellison Gonzales 1H

The most stable structure correlates with the atoms’ formal charges in the structure. Also make a note that if the chemical compound has a charge, it is best if the most electronegative atom has that negative charge on it. Typically, the best structure will have the least electronegative atom at the...

Ellison Gonzales 1H

Do you have to draw the Lewis structure to tell if they’re an acid or a base?

Ellison Gonzales 1H

Does anyone know if the charge of an ion effects the ionic radius or the size of an ion?

Ellison Gonzales 1H

Thank you Dylan, Sophia, and Dominic! This makes a lot more sense to me

Ellison Gonzales 1H

FionaHunter21 wrote:Is an anion always the atom that is polarizable and the cation is what can have high polarizing ability?

Hi!
Yes, “polarizable” applies to anions and “polarizing power”/“polarizability” applies to cations

Ellison Gonzales 1H

Hello! I was wondering why the more covalent a bond is, the more distortion there is. I understand covalent bonds and distortion are linked, but why is that? Thank you!

Ellison Gonzales 1H

Hi there! Covalent bonds can have ionic character because elements within a bond have differing electronegativities. If one element in a bond has a greater electronegativity than the other, it will attract the electron more than the other element, causing the electron to be unevenly shared (having ...

Ellison Gonzales 1H

I’m so excited for this! Thank you :)

Ellison Gonzales 1H

What about anions that are more polarizable classifies them as covalent? In other words, why is it that anions that are pulled into the shared region are classified as covalent?

Ellison Gonzales 1H

In his lecture, he also talked about charge density. Is that the same thing as its pulling ability?

Ellison Gonzales 1H

Polarizable is the ability to GET pulled (which is the anion pulled by the positive charge).
Polarizing power is the cation’s ability TO pull the anions into the shared region.

Ellison Gonzales 1H

Hello! I definitely heard several different things regarding this topic. Since I heard opposing answers, I personally always just did (final - initial) instead of thinking of it as n2 and n1. This way always worked for me or at least for the specific problems I used it on. I know this isn’t a scient...

Ellison Gonzales 1H

I know how to get the answer of ml from l, but what does ml stand for conceptually? I believe in the lecture he said that ml is the allowed values, but I don’t completely understand what that means. Thank you

Ellison Gonzales 1H

Thank you, Albert and Grace! I now understand that there are different techniques to solving this problem and that the constant R can change if you choose to use a different unit for it, thank you!

Ellison Gonzales 1H

The reason the radius of an element is larger when the ion is negative is because there is an additional e- going to the outer shell that causes more e- repulsion, therefore making anions much bigger than their neutral atom.

Ellison Gonzales 1H

The negative ion would have a larger radius because in this case, the nuclear charge stays the same (if they're the same element). The only thing that would be changing is the number of electrons, meaning the radius would be bigger. I understand the size of the radius correlating with whether it is...

Ellison Gonzales 1H

When Sapling would suggest using R=1.0974*10^7m^-1, it confused me a ton. But just to understand their reasoning, they only used this value for R when solving for wavelength to match the units for wavelength? But they did this just to fit all the work into one equation? Thank you!

Ellison Gonzales 1H

Hi! I wanted to add something that really helped me understand the right sign to use. For the Rydberg equation, we get a negative value because we are calculating the decrease in energy as the electron moves from a higher shell to a lower shell. However, when we use that value to calculate the freq...

Ellison Gonzales 1H

Hi! I agree with all the other answers here - in general, there is never going to be a loss of energy in the system because it is conserved and just transformed into different types of energy or transmitted to another object. I would say only if the question has wording similar to "total chang...

Ellison Gonzales 1H

You are indeed correct: when calculating the molar mass of a compound, you do not take into account the stoichiometric coefficient in front of the compound in the balanced chemical equation. A situation you would use the stoichiometric coefficient times the molar mass of a compound would be when yo...

Ellison Gonzales 1H

I believe the more complicated ones will be given, but like someone else said, be comfortable with the diatomics. In one of Dr. Lavelle’s office hours, he said that since we haven’t technically gone over naming elements and chemical reactions, he won’t try to trick us with that.

Ellison Gonzales 1H

Yes, that is exactly correct. Conceptually, the equations we are solving are PER photon. So at the end we would just need to figure out how many of the energy per photon we would need to get the 32.74J. First you would want to find the frequency so do c=lambda v this would give you 3.08 x 10^11 hz ...

Ellison Gonzales 1H

Hi Natallie, I found this challenging the first time I did it as well. Here's a step by step method to solve it: Step 1) When you read this problem the first time, you should be able to identify that we are discussing atomic spectroscopy in which a hydrogen atom is emitting a certain wavelength of ...

Ellison Gonzales 1H

Hi, I understand the above work, but how come we can't use the equation: En=(\frac{-hR}{n^{2}}) . How come we have to use the frequency equation? Can we not use En=(-hR/n^2)? I didn’t use the equation you wrote, but I read from other explanations on chemistry community about this question, ...

Ellison Gonzales 1H

The posts above ^ helped me figure this out. Basically, going from a higher level to a lower level causes spectral lines. To find the range of wavelengths, you must use the Rydberg equation. You use the n=7 to n=6 for the first wavelength and n=7 to n=1 for the second wavelength. The equation is v ...

Ellison Gonzales 1H

For this question, you first have to look at the given wavelength, which is 6.563 *10^-7 m (converted from nanometers). Matching this with the numbers given on the EM spectrum tells us that this light is on the wavelength of visible light, which fits in the Balmer series, which means that the light...

Ellison Gonzales 1H

How would I approach this problem? A liquid is exposed to infrared radiation with a wavelength of 9.74×10−4 cm. Assume that all the radiation is absorbed and converted to heat. How many photons are required for the liquid to absorb 32.74 J of heat? Do I need to use both E=hv and C=lambda(V)? Anothe...

Ellison Gonzales 1H

The posts above ^ helped me figure this out. Basically, going from a higher level to a lower level causes spectral lines. To find the range of wavelengths, you must use the Rydberg equation. You use the n=7 to n=6 for the first wavelength and n=7 to n=1 for the second wavelength. The equation is v ...

Ellison Gonzales 1H

Divide the total energy by the work function to see how many electrons the energy can displace. 6.78×10−7 J/4.28494×10−19 J/photon Important concepts: One photon with enough energy to displace an electron will only displace one electron. In other words, there is a one-photon to one electron ratio i...

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