Search found 35 matches

by Armo_Derbarsegian_3K
Thu Mar 16, 2017 10:11 pm
Forum: *Nucleophilic Substitution
Topic: SN2 vs "Nucleophilic sub"
Replies: 2
Views: 552

SN2 vs "Nucleophilic sub"

If a question asks us to identify a mechanism (2013 5C), would nucleophilic substitution be as valid an answer as SN2 (given as answer)?

Is there SN1?
by Armo_Derbarsegian_3K
Wed Mar 15, 2017 1:10 am
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Final 2013 Question 4
Replies: 2
Views: 406

Re: Final 2013 Question 4

Generally, you should use the log equation when also looking for pH. Otherwise, I think it is easier to use the natural log.
by Armo_Derbarsegian_3K
Sun Mar 12, 2017 2:15 pm
Forum: Student Social/Study Group
Topic: Chemistry News
Replies: 38
Views: 23050

Re: Chemistry News

Tina that is so interesting! Thank you so much for sharing. I really enjoy Dr. Olah's work! Great read!
by Armo_Derbarsegian_3K
Sat Mar 04, 2017 9:58 pm
Forum: *Nucleophiles
Topic: H2O [ENDORSED]
Replies: 4
Views: 506

Re: H2O [ENDORSED]

The lone pairs on oxygen!
by Armo_Derbarsegian_3K
Tue Feb 28, 2017 12:10 am
Forum: *Organic Reaction Mechanisms in General
Topic: Graph of first and zero order reactions
Replies: 2
Views: 495

Re: Graph of first and zero order reactions

The rate law should be the indication.
by Armo_Derbarsegian_3K
Fri Feb 24, 2017 12:57 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Intermediates in pre equilibrium
Replies: 9
Views: 1984

Intermediates in pre equilibrium

When you replace the intermediate in the rate law when doing pre equ problems, what do you do if you end up with another intermediate in your answer? ClO-+H2O<->HClO+OH- fast HClO+I-<->HIO+Cl- slow HIO+OH-<->IO-+H2O fast so the rate would be k2[HClO][I-] but HClO is an intermediate; K=[OH-][HClO]/[C...
by Armo_Derbarsegian_3K
Wed Feb 22, 2017 1:51 am
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Questions about K on pg 73 of CR
Replies: 1
Views: 249

Questions about K on pg 73 of CR

On page 73 of the CR, K was set equal to k1/k'1, why do we assume it is for the NO+NO<->N2O2 reaction? Why is K not equal to [NO2]^2/[N2O2][O2] reaction, k2/k'2? How do we determine this? Please elaborate this step. Also--is "k=2k2*K" going to be given? It seems we just set it equal at the...
by Armo_Derbarsegian_3K
Tue Feb 14, 2017 12:08 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Midterm 2014 Question 6
Replies: 1
Views: 314

Midterm 2014 Question 6

K=e^13.2 is what the CR does, but when I do it, I use the full number e^13.20417583... which varies my answer from the given, 540365, to 542626.

This is a fairly large difference and the final answer is worth 4 pts. Would we get points for doing it either way? CR or round at end way.
by Armo_Derbarsegian_3K
Fri Feb 10, 2017 2:27 am
Forum: First Order Reactions
Topic: First vs. Second Order
Replies: 7
Views: 812

Re: First vs. Second Order

How many orders can you have? Does it keep going?
by Armo_Derbarsegian_3K
Wed Feb 01, 2017 11:17 pm
Forum: Balancing Redox Reactions
Topic: Pneumonic Device
Replies: 3
Views: 417

Re: Pneumonic Device

also LEO GER

Lose electrons oxidized

Gain electrons reduced
by Armo_Derbarsegian_3K
Sun Jan 29, 2017 1:25 am
Forum: Administrative Questions and Class Announcements
Topic: Quiz Preparation
Replies: 3
Views: 500

Re: Quiz Preparation

It would be nice if they were provided right before the quizzes, so we could check our answers. This was done for 14B last year and I can see the quiz answers in my roommates old course reader from last year. That format worked much better than what we have now.
by Armo_Derbarsegian_3K
Mon Jan 23, 2017 8:08 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Memorize Values for Quiz?
Replies: 2
Views: 423

Re: Memorize Values for Quiz?

No, they should be given.
by Armo_Derbarsegian_3K
Sat Jan 21, 2017 5:21 pm
Forum: Phase Changes & Related Calculations
Topic: Practice Quizes
Replies: 10
Views: 736

Re: Practice Quizes

Some students benefit by working with peers, but others (like me) are more successful working independently. I did very well last quarter on the quizzes with the provided answers. My only incentive was my grade so I refrained from going straight to the answers. I think the method last quarter was ve...
by Armo_Derbarsegian_3K
Tue Jan 17, 2017 10:14 pm
Forum: Phase Changes & Related Calculations
Topic: Practice Quizes
Replies: 10
Views: 736

Re: Practice Quizes

Would it be possible to get a PDF of the answers to the practice quizzes so we can study them at our own pace?
by Armo_Derbarsegian_3K
Mon Jan 16, 2017 1:11 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Hess's Law
Replies: 3
Views: 363

Re: Hess's Law

When you need to cancel things from both sides. You switch signs to flip it.

for example:

A+B->C dH=x
2C->2A+D dH=y

you would multiply the top one by 2 to get A and C to cancel.
by Armo_Derbarsegian_3K
Wed Nov 30, 2016 6:58 pm
Forum: *Indicators
Topic: Selecting an indicator
Replies: 4
Views: 692

Re: Selecting an indicator

So if the equivalence point is near pH 8, why wouldn't we want one that changes color near pH 8? How exactly did you get that range of pHs for the indicator?
by Armo_Derbarsegian_3K
Wed Nov 30, 2016 3:50 am
Forum: *Indicators
Topic: Selecting an indicator
Replies: 4
Views: 692

Selecting an indicator

Why does pKin. (pKA) have to be close to pH at stoichiometric point to be an effective indicator?
by Armo_Derbarsegian_3K
Wed Nov 30, 2016 1:38 am
Forum: DeBroglie Equation
Topic: Fall 2012 Final Q1B
Replies: 1
Views: 318

Fall 2012 Final Q1B

For the equation that says:

p=hv/c -> 1pt of the grade

will h=pc/v also earn the point?

because both multiplied across -> pc=hv=E
by Armo_Derbarsegian_3K
Mon Nov 28, 2016 11:06 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: HW 12.47
Replies: 1
Views: 303

Re: HW 12.47

More oxygen=more electronegative, which stabilizes the negative charge on I, making it MUCH easier for the H to break off and protonate water to create hydronium, thus more acidic.
by Armo_Derbarsegian_3K
Thu Nov 24, 2016 5:03 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: When Should I use the ICE table?
Replies: 6
Views: 12873

Re: When Should I use the ICE table?

You can approximate if you remember to check for the 5% rule after...to make sure you are within range.
by Armo_Derbarsegian_3K
Wed Nov 16, 2016 10:10 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Why is He2 not a stable molecule?
Replies: 1
Views: 392

Re: Why is He2 not a stable molecule?

Exactly, you get a BO of 0. This means there is no bond, hence no stability as a molecule.
by Armo_Derbarsegian_3K
Tue Nov 15, 2016 11:57 am
Forum: Naming
Topic: Partial Pressure
Replies: 1
Views: 277

Re: Partial Pressure

A decrease in partial pressure means a decrease in concentration, which would shift the rxn left. I don't think partial pressure vs pressure matters because because a decrease in pressure would cause the same effect.
by Armo_Derbarsegian_3K
Sat Nov 12, 2016 3:04 pm
Forum: Naming
Topic: Naming Ligands
Replies: 2
Views: 333

Re: Naming Ligands

It is in an anionic complex.

K is a cation, so to make a neutral "salt" the [CoF6] must act as an anion and take a negative charge, hence cobaltate.
by Armo_Derbarsegian_3K
Tue Nov 01, 2016 10:12 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Electron Configuration for Fe 3+
Replies: 6
Views: 29456

Re: Electron Configuration for Fe 3+

Fe is [Ar]3d6 4s2
Fe2+ loses the 4s2
Fe3+ loses an electron from the d
so Fe3+ is [Ar]3d5

Not really an exception, just remember a full d/half full d will be much more stable(chromium/copper)
by Armo_Derbarsegian_3K
Tue Nov 01, 2016 10:04 pm
Forum: Hybridization
Topic: Unhybridized Orbitals
Replies: 2
Views: 424

Re: Unhybridized Orbitals

Look at bonding.

For example, ethylene makes a C::C and each C also makes 2 H bonds, therefore each C makes a total of 3 bonds = sp2. When you look at sp3, which is the full octet, sp2 is missing a p, and that is your un hybridized p. This is where the pi bonding happens.
by Armo_Derbarsegian_3K
Tue Nov 01, 2016 5:19 pm
Forum: Empirical & Molecular Formulas
Topic: 2013 Midterm Q2A
Replies: 1
Views: 449

2013 Midterm Q2A

For this problem: I solved for moles of each element by taking the given values and dividing by their atomic masses. i.e.: Carbon 3.27g x 1molC/12.011gC = 0.272molesC then I divided by the smallest value, got the ratio, multiplied by a number to get rid of fractions to get the answer, found grams of...
by Armo_Derbarsegian_3K
Tue Nov 01, 2016 5:10 pm
Forum: Hybridization
Topic: Fall 2012 Q6A [ENDORSED]
Replies: 4
Views: 487

Re: Fall 2012 Q6A [ENDORSED]

In the ring, the carbons each make two bonds, either to another carbon or to the nitrogen. Since the problem states hydrogens have been omitted and we know carbon likes to make 4 bonds, we would add in two hydrogens to each carbon to fulfill their octet. Therefore, each carbon actually makes 4 bonds...
by Armo_Derbarsegian_3K
Mon Oct 31, 2016 12:07 am
Forum: Hybridization
Topic: Fall 2012 Q6A [ENDORSED]
Replies: 4
Views: 487

Fall 2012 Q6A [ENDORSED]

Hello, For this problem I don't understand how you find the hybridizations. Do we assume the carbon will just make two hydrogen bonds? Or is it possible it may form a double bond? Would we have to calculate FC and figure that out, or can we assume it will just get 2 H bonds as problem only states th...
by Armo_Derbarsegian_3K
Mon Oct 24, 2016 11:59 pm
Forum: Lewis Structures
Topic: Lewis Structures wedge and dash
Replies: 1
Views: 641

Lewis Structures wedge and dash

For example: SF6's wedge and dash depiction (page 95 of CR) we show the wedges towards us and the dashes away, but we draw lines for on the top and bottom. How do we determine which get wedge and dash, and which get solid lines. Alternatively, for CH4 how do we determine which get the wedge and dash...
by Armo_Derbarsegian_3K
Mon Oct 24, 2016 11:54 pm
Forum: Lewis Structures
Topic: Octet Rule vs. Formal Charge
Replies: 2
Views: 406

Re: Octet Rule vs. Formal Charge

You want a formal charge of -1 because it is BrO-. The molecule should have a total formal charge of -1. Therefore it will make a single bond and each atom will have 3 lone pairs.
by Armo_Derbarsegian_3K
Mon Oct 24, 2016 11:50 pm
Forum: Lewis Structures
Topic: workbook Quiz 2 preparation #7
Replies: 3
Views: 339

Re: workbook Quiz 2 preparation #7

The other oxygen should form a double bond as well. So you get Xe with a lone pair, both Fs single bonded with 3 lone pairs, and the 2 Os double bonded with 2 lone pairs. :O: .. || .. :F - Xe - F: .. || .. :O: This Lewis structure will give each atom a formal charge of 0 and will be the biggest cont...
by Armo_Derbarsegian_3K
Mon Oct 17, 2016 4:46 pm
Forum: Formal Charge and Oxidation Numbers
Topic: SO4^2- Lewis Structure [ENDORSED]
Replies: 1
Views: 493

SO4^2- Lewis Structure [ENDORSED]

I understand that since S is in the n=3 -> l=0,1,2 meaning it can use the d orbital when bonding. However, in the example in class, we get 2 S double bonds with O and 2 S single bonds with 0, giving S 12 shared electrons, while the d orbital can hold 10. So what happens with the other 2 electrons no...
by Armo_Derbarsegian_3K
Mon Oct 10, 2016 6:05 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Integrated Exercises on Infrared Spectroscopy
Replies: 1
Views: 370

Re: Integrated Exercises on Infrared Spectroscopy

To start off,

You should visualize it as v/c=3600cm^-1
then solve for v
that will give you a.

for b,
use the equation E=hv
and solve for E.

for c,
multiply the E from (b) by Avogadro's number to determine the energy for a mole.
by Armo_Derbarsegian_3K
Wed Oct 05, 2016 6:12 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: quiz 1 fall 2014 prep #10
Replies: 4
Views: 641

quiz 1 fall 2014 prep #10

Hello, I did #10 and I was looking at the answers in the back and noticed: "USE BOHR EQU. FOR H ATOM (ANY 1e- H-LIKE ATOM, Li^2+): En = -2.178x10^-18 J (Z^2/n^2) for n=1,2,3.... j=joules, z=atomic number, n=energy level" What is the difference between that equation and using -hR? When do w...
by Armo_Derbarsegian_3K
Thu Sep 29, 2016 9:40 pm
Forum: Properties of Electrons
Topic: Kinetic Energy of Electrons [ENDORSED]
Replies: 4
Views: 1481

Re: Kinetic Energy of Electrons [ENDORSED]

I believe the formula finds the (minimum) energy needed to remove a single electron. Therefore, I think it is an increase in kinetic energy of a single electron.

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