Search found 44 matches

by Ara Yazaryan 1E
Tue Mar 14, 2017 7:28 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: Cell Diagram
Replies: 3
Views: 619

Re: Cell Diagram

AgBr is being oxidized from 0 to +1, and subsequently Br- is being reduced from -1 to 0. This makes AgBr the anode and Br- the cathode, this is why they are included.

Hopefully that is the correct way to answer your question :)
by Ara Yazaryan 1E
Tue Mar 14, 2017 7:22 pm
Forum: Student Social/Study Group
Topic: Strategies for studying for the final
Replies: 7
Views: 941

Re: Strategies for studying for the final

That conceptual study guide sounds like a good idea! I may try that
by Ara Yazaryan 1E
Thu Mar 09, 2017 4:19 pm
Forum: Student Social/Study Group
Topic: Midterm Review
Replies: 1
Views: 428

Re: Midterm Review

Which one? The Midterm Review Session or the Midterm answer review? I believe both should have been posted here on Chemistry Community.
by Ara Yazaryan 1E
Thu Mar 09, 2017 4:17 pm
Forum: *Cycloalkanes
Topic: "iso" naming
Replies: 4
Views: 1267

Re: "iso" naming

Iso is not taken into alphabetical account, and it comes whenever there is a fork in the carbon substituent chain. For example: "isoethyl"
by Ara Yazaryan 1E
Sun Mar 05, 2017 5:38 pm
Forum: *Alkanes
Topic: sec and tert
Replies: 2
Views: 370

Re: sec and tert

I don't believe we will be using the term "sec" quite yet. "Tert" is for when the carbons are perpendicularly arranged in a cross-shape, so you need a minimum of 4 carbons (Butyl).
by Ara Yazaryan 1E
Fri Mar 03, 2017 12:43 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8205
Views: 1433599

Re: Post All Chemistry Jokes Here

Thought this was Appropriate:
by Ara Yazaryan 1E
Fri Mar 03, 2017 12:39 pm
Forum: *Cycloalkanes
Topic: Tert- Butyl
Replies: 2
Views: 369

Re: Tert- Butyl

I may be incorrect, however I think Iso- is used when the carbon are arranged in a linear chain. Thus Tert would be used when they are all perpendicular to each other, as seen in the Course Reader. I found this link to be very helpful, and you may as well :) http://web.chem.ucla.edu/~harding/IGOC/C/...
by Ara Yazaryan 1E
Tue Feb 21, 2017 8:47 pm
Forum: General Science Questions
Topic: Significant Figures
Replies: 1
Views: 339

Re: Significant Figures

Significant figures should be computed at the end yo give the most accurate answer possible. If we take sig figs at each step of the problem our answer would have a heavy rounding bias.
by Ara Yazaryan 1E
Tue Feb 21, 2017 8:46 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate Law Intermediate Slow before fast
Replies: 2
Views: 430

Re: Rate Law Intermediate Slow before fast

The intermediate can never be part of the rate law since it is consumed in the reaction. When this happens, substitute in for the intermediate in terms of its reactants.
by Ara Yazaryan 1E
Tue Feb 14, 2017 9:08 pm
Forum: Administrative Questions and Class Announcements
Topic: Half-reactions
Replies: 1
Views: 317

Re: Half-reactions

For this case water is not being included in the reaction, rather the half reaction is occurring in an acidic solution. These means we use water and H+ to balance our oxygen atoms.
by Ara Yazaryan 1E
Tue Feb 14, 2017 11:37 am
Forum: Calculating Work of Expansion
Topic: 9.47
Replies: 2
Views: 494

Re: 9.47

The change in entropy is still the same, and you still would use ln in this case. Yet no work is done in free expansion, so the delta s of the surroundings is zero and q is zero. Only the internal entropy of the system increases in the irreversible process.
by Ara Yazaryan 1E
Fri Feb 10, 2017 8:07 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolysis: Water 1/2 Rxn
Replies: 1
Views: 355

Re: Electrolysis: Water 1/2 Rxn

Well the first to you gave are the same reaction, except one is the oxidation and the other is the reduction reaction. As for the third reaction, that is for the formation of water from diatomic hydrogen and oxygen. Thus the question would have to explicitly state "water is formed from hydrogen...
by Ara Yazaryan 1E
Fri Feb 10, 2017 7:54 pm
Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
Topic: Electrolysis
Replies: 1
Views: 353

Re: Electrolysis

Electrolysis is whenever an electron current is used to drive a reaction that may otherwise be non-spontaneous (+delta G). Redox reactions are thus often examples of electrolysis since they may not always be spontaneous and electrodes provide an electric current.
by Ara Yazaryan 1E
Tue Feb 07, 2017 6:40 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Cell Diagram Notation
Replies: 2
Views: 295

Re: Cell Diagram Notation

If I am correct yes the order does matter. This is based off whether it is the anode or cathode, in which it would go from the reactant being reduced or oxidized to the end result. Someone else feel free to add input.
by Ara Yazaryan 1E
Fri Feb 03, 2017 4:47 pm
Forum: Balancing Redox Reactions
Topic: Electrodes
Replies: 2
Views: 343

Re: Electrodes

An electrode is always needed in an electro-chemical reaction. That is how electrons are transferred in the first place, a key component of any cell system.
by Ara Yazaryan 1E
Fri Feb 03, 2017 4:46 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Extensive v Intensive
Replies: 2
Views: 410

Re: Extensive v Intensive

Intensive properties can be considered more useful in Chemical Applications because they are particularly helpful in the identification of chemical substances since they are not dependent on the amount of matter present in a system (as extensive properties are). For example, think of a colorful ruby...
by Ara Yazaryan 1E
Tue Jan 31, 2017 10:17 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 1 Preparation Answers
Replies: 130
Views: 17426

Re: Quiz 1 Preparation Answers

BetcyGaspar_3C wrote:I do believe we use the equation deltaS=qrev/T,by plugging in 200J/(273+20) you will get the answer.


Thank you so much!
by Ara Yazaryan 1E
Tue Jan 31, 2017 1:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 1 Preparation Answers
Replies: 130
Views: 17426

Re: Quiz 1 Preparation Answers

Could someone explain to me how to get #10 please? I am confused because we do not know the final temperature.
by Ara Yazaryan 1E
Wed Jan 25, 2017 9:01 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz #1
Replies: 1
Views: 311

Re: Quiz #1

It depends on what the question asks for, it could be either kJ or J depending on what is given and what is most convent to use for the answer.
by Ara Yazaryan 1E
Wed Jan 25, 2017 9:00 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Internal Energy Equation
Replies: 1
Views: 225

Re: Internal Energy Equation

I believe we would use it to find the specific heat (C) of a monatomic gas, however it is also used to prove that equation.
by Ara Yazaryan 1E
Thu Jan 19, 2017 6:07 pm
Forum: Administrative Questions and Class Announcements
Topic: Organic Chemistry Workbook
Replies: 2
Views: 456

Re: Organic Chemistry Workbook

If I am correct we will be using it in the second half of the quarter, Dr. Lavelle should tell us when we should start bringing it to class.
by Ara Yazaryan 1E
Thu Jan 19, 2017 6:06 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Ch.8 #51
Replies: 1
Views: 242

Re: Ch.8 #51

In this case, energy is released when TNT is consumed. Thus it would be positive since the surrounding environment is getting an increase in energy. If the reaction was endothermic (e.g. bonds were formed) then the reaction energy would be - since energy is used up.

Hope that helps!
by Ara Yazaryan 1E
Fri Jan 13, 2017 9:29 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Chapter 9 Question 31
Replies: 1
Views: 308

Re: Chapter 9 Question 31

If I am correct the 3/2 is simply given by the formula for the molar heat capacity of a monatomic ideal gas at constant volume. That is my opinion, but it amy not be correct so someone else's input would be helpful.
by Ara Yazaryan 1E
Fri Jan 13, 2017 9:26 pm
Forum: Calculating Work of Expansion
Topic: Work Done
Replies: 1
Views: 350

Re: Work Done

Because the negative sign signifies that energy is released from the system. I think you were under the impression that this was akin to a number-line sort of scale, which is not the case here. -300kJ realized by a system is thus more work than -200kJ. Hope that helps, cheers.
by Ara Yazaryan 1E
Thu Dec 01, 2016 8:53 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: ICE Table
Replies: 3
Views: 575

Re: ICE Table

The table is simply used to help determine the change in moles of reactants and products before and after a reaction takes place. Thus you would use it in acid base reactions, titrations, etc.

Hope that helps :)
by Ara Yazaryan 1E
Thu Dec 01, 2016 8:51 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: 3.17
Replies: 1
Views: 340

Re: 3.17

Assuming you mean Chapter 13, problem 17: The problem is asking you to generally predict the pH region (acidic or basic) where these buffers will be effective. Thus for part c, since KHP04 can give off a hydrogen it would act as an acid and thus be most effective as a buffer above pH 7., and Potassi...
by Ara Yazaryan 1E
Thu Nov 24, 2016 2:27 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: using log
Replies: 2
Views: 354

Re: using log

Well log is short for logarithm, which is an essential way of expressing pH. pH describes the concentration of H+ ions in a solution, thus describing the strength of the solution (i.e. it's parts of Hydrogen or PH). Log is simply used to appreviate. Conversely there is pOH, as described in the cours...
by Ara Yazaryan 1E
Thu Nov 24, 2016 2:23 pm
Forum: Lewis Acids & Bases
Topic: Determining which compound is stonger
Replies: 2
Views: 444

Re: Determining which compound is stonger

If I am correct, it is for the reason you cited. Because Chlorine is more electronegative, it holds onto its electrons. Thus it is more likely to give off an H+ ion, which would thus make it a stronger acid.

Hope that helps! :)
by Ara Yazaryan 1E
Thu Nov 17, 2016 10:07 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Polydenates & Naming
Replies: 2
Views: 507

Re: Polydenates & Naming

For your first question, the easiest way is just to memorize the handy list Dr. Lavelle gave us. I guess you could draw out the Lewis structure to find the number of bonding sites in a ligand, but memorization is much easier (at least in my opinion). And for the second question, the prefixes (bi, tr...
by Ara Yazaryan 1E
Thu Nov 17, 2016 10:02 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Kp and n
Replies: 1
Views: 466

Re: Kp and n

You would omit solids and liquids, including only gases and aqueous compounds.
by Ara Yazaryan 1E
Tue Nov 08, 2016 9:36 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Ch 17 Q 33 d
Replies: 1
Views: 313

Re: Ch 17 Q 33 d

Oxalate is bidentate because each of the oxygen atoms serves as an area where oxalate can bind with other atoms. Since it has two oxygen atoms therefore it is bidentate.
by Ara Yazaryan 1E
Mon Oct 31, 2016 9:28 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: When to use P sub x, P sub y and P sub z
Replies: 1
Views: 320

When to use P sub x, P sub y and P sub z

Hello all, I am confused as to when we should use P sub x, P sub y and P sub z in our electron configurations and when we could just write 2p5 or such. I believe I heard Professor Lavelle say that they are interchangeable and that the p sub is merely to help observe the sub-shells. Is this true, bec...
by Ara Yazaryan 1E
Wed Oct 26, 2016 9:26 pm
Forum: Octet Exceptions
Topic: Half Full d^5 and Full d^10 Subshells
Replies: 4
Views: 784

Re: Half Full d^5 and Full d^10 Subshells

The only exceptions we are expected to know are Cu and Cr, which in this case would be 4s1 3d5 and 4s1 3d10 respectively.
by Ara Yazaryan 1E
Wed Oct 26, 2016 9:23 pm
Forum: Trends in The Periodic Table
Topic: D-block valence electrons? [ENDORSED]
Replies: 4
Views: 4044

Re: D-block valence electrons? [ENDORSED]

You take your valence electrons as everything after the noble gas configuration.

So for example, Zinc would have 12 valence electrons from the 3d10 4s2 that comes after [Ar]

Hope that answers your question
by Ara Yazaryan 1E
Wed Oct 26, 2016 9:20 pm
Forum: Trends in The Periodic Table
Topic: Quiz 2 Question
Replies: 1
Views: 363

Re: Quiz 2 Question

It's the parts of chapter 2 that wasn't on quiz 1 and all of Chapter 3
by Ara Yazaryan 1E
Wed Oct 19, 2016 8:24 am
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Question on Chapter 3, Question 19? [ENDORSED]
Replies: 4
Views: 634

Re: Question on Chapter 3, Question 19? [ENDORSED]

3.19 part e) First take into consideration the actual electron configuration of Ni. When finding out the configuration take into account that the d subshell acts as a lower charge so should be in front of the configuration. So naturally, Ni configuration is [Ar]3d84s2 it is 3d8 because if you count...
by Ara Yazaryan 1E
Tue Oct 18, 2016 10:17 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Question on Chapter 3, Question 19? [ENDORSED]
Replies: 4
Views: 634

Question on Chapter 3, Question 19? [ENDORSED]

Hello all, Could someone please explain 3.19 part e It asks to give the "ground state electron configuration and number of unpaired electrons for Ni+2" The answer I got was 3d6 4s2 with no unpaired electrons but the answer the text gave was "3d8 and 2 unpaired electrons". Could s...
by Ara Yazaryan 1E
Thu Oct 13, 2016 7:24 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Quiz 1 Fall 2015 #3 [ENDORSED]
Replies: 3
Views: 598

Re: Quiz 1 Fall 2015 #3 [ENDORSED]

Are we suppose to double the speed if its +/- to cover the entire range in all Heisenberg uncertainty problems then? Correct me if I am wrong, but on the Heisenberg problem in the practice quiz we turn in we do not double it because we want the minimum error and adding that uncertainty would rather...
by Ara Yazaryan 1E
Thu Oct 13, 2016 7:22 pm
Forum: Balancing Chemical Reactions
Topic: Balancing Chemical equations too slow... any advice? [ENDORSED]
Replies: 18
Views: 1879

Re: Balancing Chemical equations too slow... any advice? [ENDORSED]

Personally I balance metals or other elements that are not H or O (such as C, N, Al, etc...) before I balance H and O. This is because most of the time there is some product such as H2 or H20 that i can use to help balance the equation at the end.
by Ara Yazaryan 1E
Thu Oct 06, 2016 6:24 pm
Forum: Student Social/Study Group
Topic: Armenian Study Group
Replies: 2
Views: 669

Armenian Study Group

Glancing through the usernames, I noticed that I am certainly not the only Armenian student in Chemistry 14A.

Would any other Armenians care to form a study group? (All other nationalities are welcome too of course, I just want friends to study with! :) )

Ara Yazaryan
by Ara Yazaryan 1E
Thu Oct 06, 2016 6:20 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Collapse/Localize to a Nucleus [ENDORSED]
Replies: 1
Views: 339

Re: Collapse/Localize to a Nucleus [ENDORSED]

Well the purpose of this example is to show that ion fact electrons do not collapse to or are localized at the nucleus. Rather they exist in electron energy levels or "shells" around the nucleus, many times the diameter of the nucleus itself. The Indeterminacy principle shows us that the a...
by Ara Yazaryan 1E
Wed Sep 28, 2016 5:58 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Post-Module Assessment #22-23
Replies: 5
Views: 4479

Re: Photoelectric Effect Post-Module Assessment #22-23

Yea you ALMOST finished the problem. What you found is the Energy of the PHOTON, but it is asking for the KINETIC energy. Therefore, because E(photon) - E(work function) = E (excess/kinetic energy)... 1.024998 x 10^-18 - 7.22 x 10^-19 (gotten from the previous problem) = 3.03 x 10^-19 J, which is B...
by Ara Yazaryan 1E
Mon Sep 26, 2016 7:04 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Post-Module Assessment #22-23
Replies: 5
Views: 4479

Re: Photoelectric Effect Post-Module Assessment #22-23

Question Number Two To start off: Convert nanometers to meters since that is the unit we need to divide the speed of light by. 1 nm = 10^9 meters Thus 194 nm turns to 1.94 x 10^-7 m Then plug this into speed of light = (wavelength)(frequency) 3 x 10^8 = (1.94 x 10^-7)(frequency) Thus you get the fre...
by Ara Yazaryan 1E
Mon Sep 26, 2016 6:41 pm
Forum: Photoelectric Effect
Topic: Photoelectric Effect Post-Module Assessment #22-23
Replies: 5
Views: 4479

Re: Photoelectric Effect Post-Module Assessment #22-23

So for your first question.

Energy = (Frequency)(h)

h is Planck's constant which is 6.63 x 10^-34 J.s

So if you plug it into the formula you get:

(1.09x10^15)(6.63 x 10^-34) which thus gives you 7.2267x10^-19 J

:)

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