CHEMISTRY COMMUNITY

GFolk_1D

I think it's always best to ensure your answer makes sense for the reaction as a method to check too! For example, if we got an order that was an extremely high numbe, something most likely is off

GFolk_1D

I believe the pseudo first order equation is especially applicable in the lab and helpful in solving for undetermined values regarding a specific reaction

GFolk_1D

I think going over some of the questions other students have asked on Chem Community is helpful in ensuring you understand every aspect of the topics and maybe help pick up on concepts you missed!

GFolk_1D

Is there a specific formula to use to solve for the individual reactant orders when given values in a table such as in 7A.17?

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Does anyone know of a good video or practice problems relating to catalysts?

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I noticed this too... I believe its a solutions manual error

GFolk_1D

The logQ is especially helpful if calculating/given the pH!

GFolk_1D

I think in that problem, the question didn't require you to use the n value in further steps so it did not matter if you simplified the final equation

GFolk_1D

I believe if you treated it as the cathode the Ecell would be negative (which it tells you its a positive 0.061)

GFolk_1D

Hi! I understand that standard cell potentials are based upon references to the SHE model but could some one further explain what exactly the SHE entails?

GFolk_1D

When exactly is the cell potential considered at standard conditions?

GFolk_1D

I am confused on this as well, when do we need to introduce Pt into the system?

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Hi! For anyone who learns well off of video tutorials Khan Academy has some great ones for this section! https://www.khanacademy.org/science/che ... -reduction

GFolk_1D

This is super helpful thank you!

GFolk_1D

I'm a bit confused about this as well because that delta G equation can also be applied when K is used (the equation is at equilibrium)

GFolk_1D

"K is the constant of a certain reaction when it is in equilibrium, while Q is the quotient of activities of products and reactants at any stage of a reaction." Therefore, this equation depicts delta G at equilibrium.

GFolk_1D

When delta G is negative, the reaction is spontaneous and will shift towards the products. When it is positive, the reverse reaction is spontaneous and will shift towards the reactants.

GFolk_1D

Hi! Will there still be UA review sessions today despite the holiday?

GFolk_1D

Hi! Does anyone know where to possible find more practice problems regarding applying Le Chatelier's Principle?

GFolk_1D

I believe you assume you are using one mole in the reaction

GFolk_1D

What is the significance of whether or not a reaction is spontaneous? How do we apply this is real-world situations?

GFolk_1D

The naught above the S indicates standard state.

GFolk_1D

Hi does anyone know if Lyndon's workshop is still happening tonight?

GFolk_1D

Are deltaH and q interchangeable?

GFolk_1D

Would the problems always specify whether it's reversible or irreversible? If not, how can we assume?

GFolk_1D

Also it says that no heat is lost to surroundings so we can assume that heat moves out of the copper and into the water, eventually making their temperatures equal to one another.

GFolk_1D

In this case would it be necessary to convert the pressure from Torr to atm before plugging it into the equation?

GFolk_1D

I believe in this example he was more emphasizing the process of solving those type of problems and wanted to show us accurate calculations (before sig fig rounding)

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GFolk_1D

Does anyone know where and when we can pick them up?

GFolk_1D

There are some instances where you can assume without the actual value such as when you break a bond (endothermic as energy is required to break the bond)

GFolk_1D

I am a bit confused on this topic. Could someone please use an example of how phase changes are taken into account?

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GFolk_1D

Hi! I found this video to be very useful on this topic. https://www.khanacademy.org/science/che ... -solutions

GFolk_1D

Also, if the moles of gas on either side of the reaction (and therefore space taken up in the volume) are equal than a change in pressure has no effect

GFolk_1D

This is a great summary of the concept! https://www.khanacademy.org/science/che ... -principle

GFolk_1D

However, remember that if the reaction is a exothermic reaction, adding heat will result in the formation of reactants

GFolk_1D

Hi this is a pretty involved question and I was confused at first as well but the step by step solution in the Solutions Manual was really helpful!

GFolk_1D

I found this worksheet online too which can give you a couple more practice problems on the topic. http://mmsphyschem.com/lechatP.pdf

GFolk_1D

This is true however remember that the actual equilibrium ratio remains the same. Only temperature can change K. :)

GFolk_1D

I am also a bit confused on this topic. Can someone please explain the difference between the quick way and the actual reasoning to solve these types of problems? Thanks

GFolk_1D

Yes! Because it involves the breaking of the bond between the two X molecules to form two separated X molecules we know that energy aka heat had to be put into the reaction to overcome the bond energy. Therefore it is endothermic.

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So would anything between k > 10^3 and k > 1 be only slight favoring?

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Write the equilibrium constant fir the reaction 2 AgNO3 (aq) + 2NaOH (aq)-----> Ag2O (s) + 2NaNO3 (aq) + H2O (l)

I'm a bit confused as to how to take the net ionic equation into account. Thanks!

GFolk_1D

If you are referring to 5G.1 part c, they aren't asking you to calculate the partial pressure but rather want you to state that the statement is false. Equilibrium reactions are affected by the presence of both products and reactants.

GFolk_1D

I believe that book sometimes does it differently and keeps the halogens in the equations either way but I was confused about this too.

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I believe so and I think he wanted us to heavily focus on the description box 6E.1 in particular

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Does anyone know of any helpful videos or images to help me picture how chelates function? Thanks!

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An analogy that helped me was that of a rectangle and a square.... a square is always a rectangle but a rectangle isn't always a square. The same goes for these terms as amphiprotic is always amphoteric but amphoteric molecules are not always amphiprotic

GFolk_1D

How can you tell which is the base and which is the acid in the formula:

H2O2 + SO3 -----> H2SO5

I tried drawing lewis structures but still don't quite understand. Thanks!

GFolk_1D

I understand the concept of a coordination sphere but am a bit unsure of how to identify a ligand versus other molecules that would not be included. Can someone explain this is detail please? Thanks!

GFolk_1D

Has anyone seen any helpful videos to explain/help memorize how to name compounds? Thanks!

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I believe you would need more information to identify exactly which shape it is such as hybridization or specific numbers of lone pairs/bonding pairs

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As someone stated previously, I think bismuth subsalicylate, or Pepto-Bismol, is an example of an industrial coordination compound.

GFolk_1D

Here's what I gathered...
- it is an example of a cage-like molecule
- it is square planar
- Fe is bound to the porphyrin ligand to form a heme complex
- the heme complex plus a protein creates myoglobin (Fe binds to 1 O2)
- it plays a role in the transport of O2 in the muscle cells

GFolk_1D

the shape will be trigonal planar around each C atom

GFolk_1D

GFolk_1D

If a molecule has resonance (some double bonds and some single bonds) and therefore a few pi bonds can any of the atoms rotate?

GFolk_1D

If a molecule has two bond pairs and 3 lone pairs (AX2E3) it is linear in shape and therefore has a bond angle of 180 degrees.

GFolk_1D

The lone pairs are placed based on repulsion strengths:

lone pr-lone pr>lone pr-bond pr>bond pr-bond pr

Therefore, by placing the lone pair on the equatorial plane, it allows for repulsion strengths to play out

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GFolk_1D

I found this Khan Academy video to be really helpful on explaining this topic! https://www.khanacademy.org/science/che ... amagnetism

GFolk_1D

Hi! I found this link to be very helpful in explaining the topic: https://chem.libretexts.org/Bookshelves ... _Chemistry)/Chemical_Bonding/Fundamentals_of_Chemical_Bonding/Bond_Order_and_Lengths

GFolk_1D

Not sure where this quizlet is from but it was really helpful for me to memorize! https://quizlet.com/291777131/vsepr-shapes-flash-cards/

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This video was really helpful for me to visualize. https://www.youtube.com/watch?v=vHXViZTxLXo

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If anyone has any issues opening the Sapling after purchasing it from the UCLA bookstore I called the company and it was really helpful. I just had to send a picture of my receipt and etext code and they registered my account for the class.

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Does anyone know if test 2 is cumulative or just the topics covered from the midterm to the test? Thanks!

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In class he suggested about a week but given it's all free response it may take longer

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GFolk_1D

I think it also has to do with that H is the most common element. It has several uses and forms cations very easily.

GFolk_1D

-1, 0, 1

-2, -1, 0, 1, 2

-1, 0, 1

-3, -2, -1, 0, 1, 2, 3

GFolk_1D

Could someone please explain part a as well please? I am confused about this question.

GFolk_1D

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 "coinage" metals (Cu, Ag, Au).

GFolk_1D

I was confused about this too. I thought we were supposed to switch the 4s and 3d orbitals when writing out the configuration. Why is it 3d then 4s in the book? Must the 3d be filled to switch back to before the 4s? Thanks.

GFolk_1D

Hi, does anyone know if we must memorize which elements are metals, nonmetals, and metalloids or will it be indicated on the periodic table given to us? If so, are there any tips to memorizing which is which? Thanks!

GFolk_1D

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 "coinage" metals (Cu, Ag, Au)

GFolk_1D

The elements Ga, Ge, As, Se, and Br lie in the same period in the periodic table. Write the electron configuration expected from the ground-state atoms of these elements and predict how many unpaired electrons, if any, each atom has.

GFolk_1D

Hi here's a diagram of Aufbau's Principle, hope this helps clarify!

GFolk_1D

Electron affinity decreases down the groups and increases across the periods because the electrons added are closer to the nucleus creating a stronger attraction and tighter hold.

GFolk_1D

Because the momentum and position are uncertain, the energy may be uncertain as well. Sometimes, the window of uncertainty is given and you could use the lowest value in this region to calculate the approximate lowest energy level.

GFolk_1D

I hope this image helps clarify as well!

GFolk_1D

Both of these Rydberg constants are equal and vary just because of their units.

for E=-hR/n^2.... 3.28984 * 10^15 Hz should be used and that is what is given on the formula sheet

GFolk_1D

Will there always be a positive wavelength of light emitted with e- transitions no matter if it's moving up or down energy levels?

GFolk_1D

In 1.0s, a 60 W bulb emits 11 J of energy in the form of infrared radiation (heat) of wavelength 1850 nm. What is the energy per photon of light emitted? How many photons of infrared radiation does the lamp generate in1.0s?

GFolk_1D

Hi! I was a bit confused about this topic as well and found this video to be really clear! Hope this helps. https://www.youtube.com/watch?v=1bHipDSHVG4

GFolk_1D

Yes this is possible. However, they would have to have the exact same wavelength and frequency.

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Quantized objects have a discrete numerical value. For example, an electron cannot jump energy levels without having exactly the amount of energy needed to move (no more no less). Because there is no halfway point, it is quantized.

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The information the detector picks up tells us about the energy of the electron (if they are emitted) and therefore can reveal important traits of the metal and/or light source.

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Molybdenum metal must absorb radiation with a minimum frequency of 1.09 x 10^15 s^-1 before it can emit an electron from its surface. Answer the following two questions. A. What is the minimum energy needed to produce this effect? B. If molybdenum is irradiated with 194 nm light, what is the maximum...

GFolk_1D

Hi! I was confused about this at first as well but my TA explained that since you are looking for the specific number of moles of nitrogen atoms each plant will receive, you need to relate the final mole amount to the amount of N moles in the original compound. Since the compound NH4NO3 has 2 nitrog...

GFolk_1D

Solid boron can be extracted from soli boron oxide by reaction with magnesium metal at a high temperature. A second product is solid magnesium oxide. (b) What mass of boron can be produced when 1.25kg or boron oxide is heated with 125kg of magnesium? I converted the kg to g and then solved for the m...

GFolk_1D

Hi! I wasn't sure which topic to place this under and figured this was closest to general chemistry basics.... does anyone have any tips on help with nomenclature? I do not have a strong background in chemistry and am looking for some help with understanding the compound names etc. Thanks!

GFolk_1D

A solution is prepared by dissolving 0.500g of KCl, 0.500g of K2S, and 0.500g of K3PO4 in 500mL of water. What is the concentration in the final solution of (a) potassium ions; (b) sulfide ions? Would it be appropriate to group the compounds and their masses together at the beginning of the problem ...

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