CHEMISTRY COMMUNITY

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In the Green textbook 3.5-8, how do we know where the chlorine or bromine atoms go since there are only two carbons? Thanks!

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For Final Winter 2015 #7BC, can someone explain why you solve this way?
thanks

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For Final Winter 2015 #6C, what is the reaction co-ordinate mean?
thanks

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For Final Winter 2014 #6 and 7, how would we have known to write out all these steps and what is the rate law for?
Thanks

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Hi,
For Final Winter 2014 #5B, where does the H+ go after the Br is added to the CH3(CH2)OH? Does it go to the second CH2?
Thank you!

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Can some please show the work that you do to get the answer for #11 on the practice quiz 1 please?

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Thank you! I tried that method for #11 and didn't get the right answer for some reason.

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Hi,
What will quiz 3 cover and can the answers to the practice quiz be posted please?
Thanks!

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Hi, how do you do 5 and 11 on prep quiz 2?
Thanks!

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Will the extra post-midterm review session be videoed?
Thanks :)

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Hi,
Is the second book that we got with the course reader what we are meant to be reading through along with the O-chem material from now on?
Thanks!

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Hi,
How do you do number 11?

Thanks!

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Great! That makes sense! Thank you!

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How is order related to the mechanism? What is an example of when we would use the method from the course reader for multiple reactants that all change conc? What does it mean that a catalyst is saturated in a 0th order reaction?

Thanks!

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For the pre-equilibrium approach: What if there are more than two steps in the mechanism? Also, how did you go from rate = k1 [CHBr3] ((k2[Br2])/k' 2) to rate = k [CHBr3][Br2]?

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N2O5 decomposes by a first-order run. Whats the initial rate of decamp when 3.45g is confined in 0.75L container and heated to 65C? k=5.2E-3.

I understand the answer, but was wondering if we should just ignore the temp?

Thanks!

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Can some one explain question 1 and 5 please? Also, can we do calculations with any unit of time?
Thank you!

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What if there are more than two steps in the mechanism? Also, how did you go from rate = k1 [CHBr3] ((k2[Br2])/k' 2) to rate = k [CHBr3][Br2]?

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Would it be possible to get the answers to the practice quiz please?

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Thank you; that makes sense. Though why are the other wrong?

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Hi, Which of these process lead to an increase in entropy? a. pressure of 1mol oxygen is allowed to double isothermally b. carbon dioxide is allowed to expand isothermally to 10 times its original volume c. the temp of 1 mol of He is increased at constant pressure d. Nitrogen gas is compressed isoth...

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Hi,
I couldn't see the set up of the demo, can someone explain what happened and why and what the take away was please?
Thank you!

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Hi,
What would ion-selective electrodes for Na+ or K+ be used for, like measuring potassium in someone's blood?
Also, Eo imply equilibrium as well as standard conditions? Why is nerst eqn at 25C? I nerst just used for when concentrations are different and for electrolytic cells?
Thankyou!

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Can someone explain "if G is energy min then any decrease must be spontaneous" please?
Thanks!

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Hi,

If 2mol of an ideal gas at 300K and 3atm expands isothermally & reversibly from 6L to 18L and has a final pressure of 1.2 atm, what's w, q, and delta U.

Which eqn do we use since both volume and pressure change?
Thanks!

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Hi,
What is the difference bw delta G and delta U? When calculating using the standard free energy of formation (the 3rd method) why is it specified that it is the "of formation" i.e. does it mean the free energy change when a molecule is formed (bonds made)?
Thank you!

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Blacksmith tempers a 1.45kg made of carbon steel to 314C and then dunks it into a large vat of room temp water 25C. Assuming all the heat of is transferred to the water such that the sword ends up at 25C, and the team does not heat past its measured boiling temp 100C, what is: the mass of the water ...

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Your friend asks for a glass of exactly 400g of water at 16C. You can get tap water at 25C from the faucet and ice at 0C from your freezer. How many grams of ice and how many grams of water must you combine to make his very specific request? So I understand most of the solution, but I don't really k...

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Ahh, thank you!

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Hi, So from the lecture: 1. What does the NA stand for in the equation W=2^(NA)? it's number of particles times avogadro's number? 2. Is Wg > Wl > Ws because of the greater movement of the gas molecules than those in the other states? 3. What constitutes the residual energy to be "low;" do...

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Oh right! Thank you!

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hi,
from the course reader, can someone explain why the temperature doesn't change as heat is being added to the system?
Thank you!

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Hi, #25 says: A constant-volume calorimeter was calibrated by carrying out a reaction known to release 3.50kJ of heat in 0.200L of solution in the calorimeter (q=-3.50kJ), resulting in a temperature change of 7.32C. In a subsequent experiment, 100.0mL of 0.200M HBr(aq) and 100.0mL of 0.200M KOH (aq)...

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#21: A piece of copper of mass 20.0g at 100C is placed in a vessel of negligible heat capacity but containing 50.7g of water at 22.0C. Calculate the final temperature of the water. Assume that no energy is lost to the surroundings.

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Hi,
Sorry, here it is: a) calculate the heat that must be supplied to a 500.0g copper kettle containing 400.0g of water to raise its temperature from 22C to the boiling point of water, 100C. b) What percentage of the heat is used to raise the temperature of the water?

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hi,
why don't we need the mass or the material of the calorimeter to find its heat capacity?
thank you!

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Hi, in general, why is it that we do not always need to use moles for the calculations for enthalpy with heat capacity? also, for #21 why is it important to know that the vessel is of negligible heat capacity? also, is the final temperature of the copper equal to the initial temperature of the water...

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Hi, Why is it that we use the same delta T to find the enthalpy of the kettle as we used to find the enthalpy of the water? i.e. does the kettle also change temperature from 22 to 100 the same as the water? This seems odd to me since copper has a much lower heat capacity, though maybe that is the ke...

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Oh ok! I think I understand mostly. Thank you for the video!

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Hi,
I don't understand the difference between a reversible vs. irreversible process.
Thanks!

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I see thank you. So when Kc is small to get back to equilibrium, when a change in concentration has occurred, the production of products will be favored and visa versa?

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Thank you! I mean more like the deeper meaning please.

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Hi, can someone explain what Kc tells us please?
Thank you!

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Thank you!

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Hi, Why is a side favored when a rxn is at equilibrium? It seems like neither side should be favored if a rxn has the same forward and reverse rates? I guess I'm wondering why we can have a run at equilibrium with different concentrations on both sides, or are the rates and concentrations not related?

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Hi, Q: e- ejected from sodium. if wavelength of ejected e- is 1.1 nm, what was the frequency of the incident light? work fxn for sodium =150.6kJ/mol Why do we need to find the velocity of the ejected electron first? Why can't we use E=h(nu) to find the Ek? Is it because the electron comes out at a c...

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Hi
Why can there only be 2 electrons in an atom if n=5, l=3, ml=-1 and also if n=2, l is 1 and ml is 0?

How do you show that momentum is proportional to the number of cycles per meter?

Thank you!

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Ahh Yes! Thank you so much! :)

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Why is [Co(en)2(CN)Cl]Cl not named chlorocyanobisethylenediamminecobalt(III)chlorine but has chloride as the counter ion?
Thanks!

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Oh, ok thank you!

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ahh :) thank you

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For Quiz 3 prep are we meant to include the ethylenes attached to the ammines when we draw [Cu(dien)2]^2+?

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What was the answer for quiz prep 2 #3: lewis structure for S2O3^2- that follows the octet rule?

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4. Knowing that carbon has a valence of four in nearly all its compounds and can form chains and rings of C atoms, draw two possible chain structures for C3H4.

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2. Name Na[Co(NH3)3Cl3]
I wrote triamminetricholorocobalt(II)sodium.
Why is there meant to be an -ate on the cobalt?

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How you do find the coordination number from a given formula of a coordination complex? Thanks!

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Hi,
Why are there astrixes on some of the ligands in the table in the course reader? Thank you!

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Why are there astrixes on come of the names in course reader? I assume that they denote some special property but I'm not sure what.
Thanks!

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Is shape of coordination compounds something that we should be comfortable with?
Thanks!

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course reader p.188 Q6A: Can someone explain parts 1-3 please? I don't understand how we know how many hydrogen atoms are on each carbon without prior knowledge about proline. Thank you!

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Wow, very interesting. Thank you!

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So, MO theory allows us to find the bonding order and the magnetic properties but why does knowing those things help us i.e. what are they for?

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So, MO theory allows us to find the bonding order and the magnetic properties but why does knowing those things help us i.e. what are they for?

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Hi,
Up to what lecture does the midterm 1 cover?
Thank you!

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Yes, was referring to the bond. Thank you!

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Hi, is CN- not very strong since it is ionic?
Thanks!

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Hi,
Why do we remove the two e- from a lone pair to create a double bond when only 1 e- is actually needed to form a covalent bond? Or is my thinking incorrect?
Thanks!

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Oh, I understand! Thank you!

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Hi,
why is the electron affinity of Br so high when it usually has a charge of -1? Wouldn't that mean that it does not want another e-?
Thank you!

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With a +2 charge shouldn't we subtract 2 from 25?

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Hi,
Can anyone explain 3.9 and 3.11 please?

Thank you!

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Hi,
Can someone explain b in 67 and the part about electron repulsion in 81 please? And then 47,39,29 please :)
Thank you!

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Thank you!

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Hi,
How do you solve 15 without the Rydberg equation?
Thank you!

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How do you find the uncertainty in the kinetic energy per mole?

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Hi,
Do I need to memorize the charged of the transition metals so that I can know how to write their names?
Thank you!

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Hi,
Is there somewhere we can access the solutions to the online module assessments? No worries if not, I'll go to office hours.

Thank you!

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When the energy per photon is equal to the energy required to remove an e-, is that called the threshold energy? Thank you :)

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I'm also confused about the series and atomic spectra. :/

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right! Thank you :)

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How did you find the mass of the sodium e-?

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In lecture, I believe Lavelle said that intensity is a higher amplitude.

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Thank you very much!

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Thank you very much!

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Thank you very much!

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Thank you very much!

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Thank you very much! I'm pretty sure that the 1.02x10^-18J is actually the E of the photon so we then need to subtract from it the threshold energy from the previous problem to get 3.03x10^19J. Right?

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Hi :)

Can someone explain what this statement in the course reader means please?: "If light had only wave properties them increasing the intensity should eject e-"

Thank you!

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Hi :) Can someone explain why EM radiation is seen as light please? I know that when electrons are excited they give off photons when they are move to a different energy level in a material's atoms, but literally why are photons seen as light? Also, when stage lights are filtered through a green, re...

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Hi :) Can someone explain what the answer to the question is and the reasoning behind it please? 22. 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 two questions. A. What is the minimum energy n...

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Hi :) Can someone explain what the answer to the question is and the reasoning behind it please? Light hits a sodium metal surface and the velocity of the ejected electron is 6.61x10^5 m.s^-1. The work function for sodium is 150.6 kJ.mol^-1. Answer the following 3 questions. A. What is the kinetic e...

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Hi :) Can someone explain what the answer to the question is and the reasoning behind it please? During a summer camping weekend 4 moles of butane (C4H10) gas were used for cooking. Choose the right balanced equation for the combustion of 4 moles of butane gas. What's the net number of moles of gas ...

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