Search found 112 matches
- Sun Mar 15, 2020 10:31 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chem Community Posts Due Date
- Replies: 13
- Views: 1080
Re: Chem Community Posts Due Date
I think its still due on Sunday night :)
- Sun Mar 15, 2020 10:26 pm
- Forum: Student Social/Study Group
- Topic: Number of Chemistry Community Posts
- Replies: 45
- Views: 2399
Re: Number of Chemistry Community Posts
There were some weeks that I posted more than five questions for each week, would these "extras" count towards my total 50 for the quarter? Or would they just be not counted?
- Sun Mar 15, 2020 8:04 am
- Forum: Student Social/Study Group
- Topic: thoughtful poetry time + lavelle appreciation
- Replies: 6
- Views: 478
Re: thoughtful poetry time + lavelle appreciation
Chemistry is good
Lavelle came through with that exam
Hope you all do well :)
Lavelle came through with that exam
Hope you all do well :)
- Sun Mar 15, 2020 7:47 am
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 490
- Views: 513775
Re: Saying Thank You to Dr. Lavelle
Dear Dr. Lavelle,
Thank you for your dedication to supporting your students and providing so many resources, even after this interesting situation came down at the university.
Thank you for your dedication to supporting your students and providing so many resources, even after this interesting situation came down at the university.
- Sun Mar 15, 2020 7:34 am
- Forum: *Identifying Primary, Secondary, Tertiary, Quaternary Carbons, Hydrogens, Nitrogens
- Topic: Will the Final for 14B have Identification?
- Replies: 9
- Views: 5846
Re: Will the Final for 14B have Identification?
I don't think we'll be specifically asked about this on the final.
- Sat Mar 14, 2020 12:43 am
- Forum: Student Social/Study Group
- Topic: Tips for Staying Focused
- Replies: 64
- Views: 3576
Re: Tips for Staying Focused
I always try to not study on an empty stomach since that lack of energy won’t do me any good. I’m just trying to establish a study routine for these next few months, but I find that completely shutting off social media and other distractions helps!
- Sun Mar 08, 2020 11:13 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Instantaneous Rate
- Replies: 41
- Views: 2095
Re: Instantaneous Rate
Instantaneous rate decreases as time increases
- Sun Mar 08, 2020 11:06 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: order of reactions
- Replies: 7
- Views: 476
Re: order of reactions
The order of a reaction tells you how the concentration of reactant affects the rate.
- Sun Mar 08, 2020 11:04 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Study Advice
- Replies: 73
- Views: 6768
Re: Study Advice
For me, the step-up sessions and the drop-in sessions are the most beneficial.
- Sun Mar 08, 2020 10:58 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: units
- Replies: 11
- Views: 706
Re: units
The units are moles per liter per time in seconds
- Sun Mar 08, 2020 10:55 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Molecularity
- Replies: 12
- Views: 761
Re: Molecularity
Molecularity is the number of species in an elementary step of a reaction
- Sun Mar 01, 2020 11:14 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: first order
- Replies: 8
- Views: 612
Re: first order
First order reactions have linear rates.
- Sun Mar 01, 2020 11:08 pm
- Forum: Administrative Questions and Class Announcements
- Topic: what to know for test 2
- Replies: 10
- Views: 575
Re: what to know for test 2
Everything listed on the second page of Outline 4 and all of Outline 5.
- Sun Mar 01, 2020 10:25 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Recharging Batteries [ENDORSED]
- Replies: 10
- Views: 1331
Re: Recharging Batteries [ENDORSED]
The favorable case would be if the battery was doing work and dying. Therefore the unfavorable action would be recharging it.
- Sun Mar 01, 2020 10:13 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: Porous Disk and Salt Bridge
- Replies: 13
- Views: 1162
Re: Porous Disk and Salt Bridge
I think especially for the purpose for this class, there is no difference in efficiency between the two.
- Sun Mar 01, 2020 9:20 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Comparing Experimental Data
- Replies: 3
- Views: 313
Comparing Experimental Data
On Friday, Professor Lavelle went over the strategy for finding the overall reaction order by comparing experimental data provided in the question. On the slide it said: (RATE 2/RATE 1) = 2 = 2.0 m therefore m=1 I understand why m would equal 1 but I'm struggling to see where the expression 2.0 m ca...
- Sun Feb 23, 2020 12:20 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Conductors vs. Nonconductors
- Replies: 3
- Views: 272
Conductors vs. Nonconductors
In Friday's lecture, our first example was with 2Fe 3+ (aq) + Cu (s) --> Cu 2+ (aq) + 2Fe 2+ (aq). In this galvanic cell diagram, we used a platinum electrode in the cathode, because Fe is not a conductor, and thus platinum needed to be added. Are we supposed to know which elements are good conducto...
- Sun Feb 23, 2020 12:17 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Coulomb Unit
- Replies: 4
- Views: 400
Coulomb Unit
Can somebody briefly explain once more why we don't use the units "J/mol" of electrons to represent work, rather we use "J/C"?
- Sun Feb 23, 2020 12:14 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: "Switch" on Galvanic Cells [ENDORSED]
- Replies: 1
- Views: 164
"Switch" on Galvanic Cells [ENDORSED]
I had a quick question for clarification on the "switch" we usually include in galvanic cell diagrams. When the switch is off, that's when the difference in electrochemical potential is greatest? And once we flip the switch on the battery, the charges are allowed to diffuse, producing work...
- Thu Feb 20, 2020 2:25 am
- Forum: Balancing Redox Reactions
- Topic: Homework 6K.3 part A
- Replies: 1
- Views: 264
Re: Homework 6K.3 part A
Wait, nevermind... I think I see where I went wrong. I messed up on balancing with H2O and H+.
Reduction: 8e- + 4Cl2 --> 8Cl-
Oxidation: 5H2O + S2O32- --> 2SO42- + 10H+ + 8e-
Combined redox reaction:
4Cl2 + 5H2O + S2O32- --> 8Cl-+ 2SO42- + 10H+
Reduction: 8e- + 4Cl2 --> 8Cl-
Oxidation: 5H2O + S2O32- --> 2SO42- + 10H+ + 8e-
Combined redox reaction:
4Cl2 + 5H2O + S2O32- --> 8Cl-+ 2SO42- + 10H+
- Thu Feb 20, 2020 2:16 am
- Forum: Balancing Redox Reactions
- Topic: Homework 6K.3 part A
- Replies: 1
- Views: 264
Homework 6K.3 part A
For some reason I keep getting this question incorrect. I'd appreciate if someone can tell me where I'm going wrong? 6K.3 Balance each of the following skeletal equations by using oxidation and reduction half-reactions. All the reactions take place in acidic solution. Identify the oxidizing agent an...
- Thu Feb 20, 2020 2:03 am
- Forum: Balancing Redox Reactions
- Topic: Helpful Videos
- Replies: 2
- Views: 275
Re: Helpful Videos
Thank you for posting this!
This additional video was pretty helpful in understanding how to balance redox reactions:
https://www.youtube.com/watch?v=N6ivvu6xlog
This additional video was pretty helpful in understanding how to balance redox reactions:
https://www.youtube.com/watch?v=N6ivvu6xlog
- Thu Feb 20, 2020 2:00 am
- Forum: Balancing Redox Reactions
- Topic: Memorizing charges
- Replies: 11
- Views: 680
Re: Memorizing charges
The common ones I would definitely have locked down are O which is 2-, H which is 1+, F which is 1-. Elements by themselves (ex. diatomic molecules like Cl2) are 0.
- Wed Feb 12, 2020 8:49 pm
- Forum: Student Social/Study Group
- Topic: Constructive Criticism on Midterm Structure/Content
- Replies: 1
- Views: 248
Constructive Criticism on Midterm Structure/Content
Walking out of my midterm location, I couldn't help but overhear all the critiques/concerns students expressed after the midterm. Some of these comments surrounded the actual content the midterm tested, but also the overall structure of the exam. I wanted to create a space for students to post their...
- Wed Feb 12, 2020 3:59 pm
- Forum: Administrative Questions and Class Announcements
- Topic: A helpful equation sheet
- Replies: 4
- Views: 661
Re: A helpful equation sheet
Why is DeltaU for constant pressure being calculated using Cv? In order words, why is the change in internal energy for a system under constant pressure (DeltaU) using the Cv value in its calculations? Shouldn't DeltaU = q + w?
- Tue Feb 11, 2020 6:37 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: 4F.1
- Replies: 2
- Views: 187
Re: 4F.1
The equation used is deltaSsurroundings= (-deltaH)/T
Since temperature is in the denominator, if that value is increased, then the overall value of the expression (deltaSsurroundings) would be smaller.
Since temperature is in the denominator, if that value is increased, then the overall value of the expression (deltaSsurroundings) would be smaller.
- Tue Feb 11, 2020 6:00 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: When is q equal to dH
- Replies: 1
- Views: 111
When is q equal to dH
Under what conditions is q, heat flow, equal to change in enthalpy of the reaction?
- Tue Feb 11, 2020 5:51 pm
- Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
- Topic: Calculating standard entropy
- Replies: 3
- Views: 311
Calculating standard entropy
When would you use the equation dS= C * ln (T2/T1) and when would you include the number of moles into that equation? I notice we've used both dS= C * ln (T2/T1) and dS= n* C * ln (T2/T1) to solve problems but I'm not sure when to apply which equation.
- Tue Feb 11, 2020 5:40 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: 4F13
- Replies: 3
- Views: 225
Re: 4F13
Since both parts have to do with phase change, you can use dS = q/T = dH/T. Thus, the calculation is 1.00 mol(-6.01 kJ/mol)/273.15 K. And, the answer is -0.0220 kJ/K. For part b, you can use the same equation. First, calculate the moles of ethanol and multiply it by the molar enthalpy of vaporizati...
- Tue Feb 11, 2020 12:45 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Questions about Equation Sheet
- Replies: 3
- Views: 277
Questions about Equation Sheet
On the constant and equation sheet, I saw the equations C p = (5/2) R, C v = (3/2) R, and U= (3/2)nRT, and it brought up some questions. I know the equation to calculate heat capacity under a constant pressure is C p = (5/2) R, but for which kinds of molecules does this apply to? monoatomic or diato...
- Mon Feb 10, 2020 1:10 am
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm
- Replies: 12
- Views: 565
Re: Midterm
Will the review session on that day be covering past exam problems?
- Mon Feb 10, 2020 1:09 am
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Content
- Replies: 6
- Views: 347
Re: Midterm Content
From outline four, topics 4F through 4J will be covered.
- Mon Feb 10, 2020 1:08 am
- Forum: Ideal Gases
- Topic: Change in pressure
- Replies: 7
- Views: 490
Re: Change in pressure
Lavelle explained this in lecture once that increasing the pressure will shift the reaction to the side with less moles of gas (this is the simplified way of thinking about it)
- Mon Feb 10, 2020 1:06 am
- Forum: Ideal Gases
- Topic: Gas constant
- Replies: 10
- Views: 508
Re: Gas constant
It is crucial that you choose the version of the gas constant that has the same units as the problem you're working on, just so they cancel out and you don't introduce new units.
- Mon Feb 10, 2020 1:05 am
- Forum: Calculating Work of Expansion
- Topic: Midterm equation sheet
- Replies: 16
- Views: 681
Re: Midterm equation sheet
Thankfully it is always the same sheet used so it's pretty essential to understand it and how each equation is derived. :)
- Sun Feb 02, 2020 10:02 pm
- Forum: Calculating Work of Expansion
- Topic: Work
- Replies: 4
- Views: 149
Re: Work
For 14B, we really only have to worry about work of expansion and work of compression. ΔU = q + w where ΔU is the total change of (internal) energy of a system , q is the energy in the form of heat gained/lost by the system , and w is the energy in the form of work done on/by the system. A negative ...
- Sun Feb 02, 2020 9:35 pm
- Forum: Phase Changes & Related Calculations
- Topic: Question about Internal Energy
- Replies: 2
- Views: 129
Re: Question about Internal Energy
Actually, is this line of thinking correct?:
The change in internal energy (ΔU) is equal to the change in enthalpy (ΔH) because there is no energy being done through work (w).
ΔU= qp + w
ΔU = ΔH + (-PΔV)
ΔU = ΔH + 0
ΔU = ΔH
The change in internal energy (ΔU) is equal to the change in enthalpy (ΔH) because there is no energy being done through work (w).
ΔU= qp + w
ΔU = ΔH + (-PΔV)
ΔU = ΔH + 0
ΔU = ΔH
- Sun Feb 02, 2020 9:29 pm
- Forum: Phase Changes & Related Calculations
- Topic: Question about Internal Energy
- Replies: 2
- Views: 129
Question about Internal Energy
Why is ΔU equal to ΔH only when pressure is constant and volume doesn't change?
Is this relationship shown through any of the equations we have been working with?
Is this relationship shown through any of the equations we have been working with?
- Sun Feb 02, 2020 9:26 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Value of q
- Replies: 11
- Views: 534
Re: Value of q
Any energy lost/gained by the system must equal the energy gained/lost by the surroundings.
- Sun Feb 02, 2020 5:26 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Variables
- Replies: 3
- Views: 120
Variables
I'm having trouble mentally keeping track of all the variables we use in thermochemistry. U= internal energy P= pressure V= volume H= enthalpy ; ΔH= change in enthalpy, which sometimes is equal to q(??) q= heat ; q p = heat under constant pressure, q v = heat under constant volume w= work C= heat ca...
- Tue Jan 28, 2020 11:05 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test One
- Replies: 2
- Views: 98
Test One
Have the tests been returned yet for some? Does anyone know when is the latest we'd get our test back?
- Mon Jan 27, 2020 11:09 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Fridays Lecture (week 3)
- Replies: 1
- Views: 178
Re: Fridays Lecture (week 3)
I hope this helps :)
- Sun Jan 26, 2020 9:51 pm
- Forum: Phase Changes & Related Calculations
- Topic: enthalpy of phase changes
- Replies: 8
- Views: 226
Re: enthalpy of phase changes
Hello, In response to this question, could anyone explain why the bond enthalpies in Dr. Lavelle's example were positive AND negative? Bond energy can be described as the energy it takes to break a bond, in this case, the values would be positive. Therefore, the energy it takes to form bonds would ...
- Sun Jan 26, 2020 9:46 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: hess's law
- Replies: 5
- Views: 223
Re: hess's law
It states that because enthalpy is a state property, changes in enthalpy are additive. in other words, enthalpy change in each step of a multistep rxn can be added to give TOTAL enthalpy change.
- Sun Jan 26, 2020 9:43 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 6
- Views: 119
Re: Bond Enthalpies
I think we would just get the bond enthalpy values from a chart.
- Sun Jan 26, 2020 9:42 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Hess's Law
- Replies: 9
- Views: 402
Re: Hess's Law
Hess's Law describes that because enthalpy is a state function, it must be additive (enthalpy change at each step of a multistep reaction can be added to give TOTAL enthalpy change).
- Sun Jan 26, 2020 9:40 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard State
- Replies: 2
- Views: 89
Standard State
How do you know the standard state of a molecule? Its easy for molecules like nitrogen and oxygen, but how would we know for other molecules?
- Sat Jan 18, 2020 12:49 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Validating Approximation
- Replies: 2
- Views: 87
Validating Approximation
How do we validate the approximation of X? I know as long as X is less than 5% of the initial concentration, then the approximation is valid. However, how do you actually calculate if X is less than 5% of the initial conc.?
- Sat Jan 18, 2020 12:44 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Components that do not affect pH
- Replies: 2
- Views: 94
Components that do not affect pH
Which types of molecules don't affect the pH of a solution? For example, as discussed in 1/17 lecture, when calculating the pH, why do we not include Cl - in the reaction between HCl and NH 4 + to form the salt NH 4 Cl? Professor Lavelle said Cl - was not included because it is not involved in the r...
- Sat Jan 18, 2020 12:35 am
- Forum: Student Social/Study Group
- Topic: Notes for 1/15 Wednesday
- Replies: 1
- Views: 158
Notes for 1/15 Wednesday
Unfortunately I was unable to attend lecture and was wondering if anyone would be kind enough to post their notes from Wednesday, 1/15. I would be greatly appreciative!
- Sat Jan 18, 2020 12:33 am
- Forum: Student Social/Study Group
- Topic: Notes for 1/13 Lecture
- Replies: 4
- Views: 296
Re: Notes for 1/13 Lecture
Apologies for the cramped paper and sloppiness!
- Sat Jan 18, 2020 12:27 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Identifying Acids, Bases, and Salts in a Rxn
- Replies: 4
- Views: 226
Identifying Acids, Bases, and Salts in a Rxn
I'm still having trouble with being able to determine which components of a reaction are (weak/strong) acids or bases, or salts. I remember that we just had to memorize strong acids/bases for 14A. But if anyone can share tips on how to identify the others in a reaction please help! Also, the effects...
- Tue Jan 14, 2020 9:40 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Acids and Base Equilibria
- Replies: 4
- Views: 159
Acids and Base Equilibria
What is the difference between strong acids/bases and weak ones in terms of calculating K?
- Tue Jan 14, 2020 9:34 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Kw
- Replies: 16
- Views: 364
Kw
Is Kw the equilibrium constant for water or the ionization constant?
- Sun Jan 12, 2020 8:15 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: When to use Kc vs Kp
- Replies: 7
- Views: 179
Re: When to use Kc vs Kp
what would happen if the reactant(s) and/or products are different states? If the R or P are in different states, you calculate K c , since aqueous and gaseous solutions exist in concentrations. You really only calculate K p when all the R and P are gaseous, but even then, it is generally acceptabl...
- Sun Jan 12, 2020 8:07 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Different types of K
- Replies: 9
- Views: 256
Re: Different types of K
How do you convert from Kc to Kp? I believe this was briefly discussed in the second lecture. To convert between partial pressure and concentration for a gas, you use the Ideal Gas Equation, PV=nRT. Where, P= pressure, V= volume, n= number of moles, and (RT) are constants. To calculate pressure of ...
- Sun Jan 12, 2020 7:51 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Finding K: liquids and aqueous
- Replies: 7
- Views: 223
Re: Finding K: liquids and aqueous
To clarify,
solids are not included in the K expression because they don't necessarily have a "concentration," and liquids are not included because they consist of a pure substance?
Is this thinking correct?
solids are not included in the K expression because they don't necessarily have a "concentration," and liquids are not included because they consist of a pure substance?
Is this thinking correct?
- Sun Jan 12, 2020 7:40 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test One Content
- Replies: 6
- Views: 288
Test One Content
Where will the questions for test one be pulled from? The textbook?
Also will it cover material from Acids and Bases or just Chemical Equilibria?
Thank you:)
Also will it cover material from Acids and Bases or just Chemical Equilibria?
Thank you:)
- Sun Jan 12, 2020 7:35 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Inert Gases and Equilibrium Constant
- Replies: 4
- Views: 223
Re: Inert Gases and Equilibrium Constant
I was confused on this, too. Is this thinking correct?:
Because the equilibrium constant is a ratio of product concentration (moles/volume) to reactant concentration at equilibrium, it is unaffected by increases in pressure (by adding an inert gas) as long as the volume stays the same.
Thank you:)
Because the equilibrium constant is a ratio of product concentration (moles/volume) to reactant concentration at equilibrium, it is unaffected by increases in pressure (by adding an inert gas) as long as the volume stays the same.
Thank you:)
- Sun Dec 08, 2019 8:45 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Really helpful videos!
- Replies: 4
- Views: 480
Really helpful videos!
Hey guys I just wanted to share these videos that I found really helpful with visualizing molecular shape! And an attached chart provided by one of the TAs in a different forum. https://www.youtube.com/watch?v=nxebQZUVvTg&t=904s https://www.youtube.com/watch?v=cdo6FtSU_k8 Also, there's this help...
- Sun Dec 08, 2019 8:36 pm
- Forum: Student Social/Study Group
- Topic: Cyano vs. Cyanido
- Replies: 3
- Views: 349
Re: Cyano vs. Cyanido
I think it's just the "old" way vs the "new" way idk. It's correct to use both but it's good to be consistent with it.
- Sun Dec 08, 2019 8:33 pm
- Forum: Student Social/Study Group
- Topic: Final discussion
- Replies: 4
- Views: 422
Re: Final discussion
For some reason the word titration just threw me off so it really took me a minute to put something down.
- Sun Dec 08, 2019 8:25 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 490
- Views: 513775
Re: Saying Thank You to Dr. Lavelle
I appreciate all the resources that are provided to help us succeed in this series! Especially chemistry community because of its accessibility. Thank you, Professor Lavelle!
- Sun Dec 08, 2019 8:23 pm
- Forum: Student Social/Study Group
- Topic: Week 10 Chemistry Community
- Replies: 9
- Views: 701
Re: Week 10 Chemistry Community
I think my number of posts is off by one, is this a problem for anyone else?
- Tue Dec 03, 2019 9:14 pm
- Forum: Conjugate Acids & Bases
- Topic: 6A.1
- Replies: 6
- Views: 772
Re: 6A.1
curry 1E wrote:I get that for a conjugate acid you add an H and add + to overall charge. But, for part a), would you add the H to the H of CH3 or the H of NH2?
You would add an H to the Nitrogen atom, since the carbon atom has a complete octet already.
- Mon Dec 02, 2019 12:14 am
- Forum: Student Social/Study Group
- Topic: Notes for Wednesday's Lecture
- Replies: 6
- Views: 437
Re: Notes for Wednesday's Lecture
Jaklin Astvatsatryan wrote:.
thank you so much i really appreciate it !
- Sun Dec 01, 2019 6:22 pm
- Forum: Bronsted Acids & Bases
- Topic: Difference between Arrhenius, Bronsted, and Lewis Acids/Bases
- Replies: 2
- Views: 220
Difference between Arrhenius, Bronsted, and Lewis Acids/Bases
My TA differentiated between these types of acids and bases during discussion and I figured it might help someone if I posted it here. Arrhenius Acid: gives off H+ Base: gives off OH- B-L Acid: proton donor Base: proton acceptor Lewis Acid: electron pair (usually nonbonding 2e-) acceptor Base: elect...
- Sun Dec 01, 2019 6:17 pm
- Forum: Naming
- Topic: Naming an Anion
- Replies: 2
- Views: 181
Naming an Anion
I'm extremely confused when it comes to naming coordination compounds. In my notes I have "add 'o' to end of name if its an anion (ex. cyan ide --> cyan o ; chlor ide --> chlor o )" How do you know when the atom is an anion? Do we do this for ligands or for the metal aspect of the compound...
- Sun Dec 01, 2019 6:13 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Difference between weak acids/bases and strong acids/bases
- Replies: 6
- Views: 387
Difference between weak acids/bases and strong acids/bases
What's the most important difference between weak acids and bases vs strong acids and bases as it pertains to this class?
- Sun Dec 01, 2019 6:08 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Calculating pH for Weak Acids and Bases
- Replies: 1
- Views: 75
Calculating pH for Weak Acids and Bases
In Monday's (11/25) lecture, Professor Lavelle mentioned that we wouldn't be using the ICE table for solving the pH/pOH of weak acids and bases until 14B. But during discussion my TA was going to go through an ICE box example. Will we be using the ICE table this class or for 14B? Or will we just be ...
- Sun Dec 01, 2019 6:04 pm
- Forum: Student Social/Study Group
- Topic: Notes for Wednesday's Lecture
- Replies: 6
- Views: 437
Notes for Wednesday's Lecture
I was wondering if anyone would be kind enough to post or share their notes for the lecture before Thanksgiving (11/27). Like many students I had to fly back home. You would be doing me a tremendous favor!
Thank you
Thank you
- Sun Nov 24, 2019 9:27 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Test 2 Grades
- Replies: 10
- Views: 632
Test 2 Grades
Has anyone found out when our test 2 grades will be announced?
- Wed Nov 20, 2019 6:32 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Regions of electron density
- Replies: 5
- Views: 169
Re: Regions of electron density
VSEPR Table.pdf Really? Do you know where I can find his post?? Wow! Thank you so much this helps a lot! Quick question about the chart so in domain 6 is the angle for AX5E less than 90 degrees? And is the reason why the bond angles in AX4E2 still 90 degrees because of the two lone pairs in the axi...
- Tue Nov 19, 2019 12:46 am
- Forum: Sigma & Pi Bonds
- Topic: Sigma and Pi Bonds
- Replies: 4
- Views: 326
Re: Sigma and Pi Bonds
I'm guessing that for the purpose of this class we have to know:
single bond: sigma bond
double bond: sigma bond + pi bond
triple bond: sigma bond + 2 pi bonds
single bond: sigma bond
double bond: sigma bond + pi bond
triple bond: sigma bond + 2 pi bonds
- Tue Nov 19, 2019 12:42 am
- Forum: Sigma & Pi Bonds
- Topic: Stability of Sigma and Pi Bonds
- Replies: 4
- Views: 317
Stability of Sigma and Pi Bonds
Why are sigma bonds more stable? Similarly, it was said in lecture that pi bonds are weaker because the electrons "are more exposed." In what way can electrons be "more exposed"? Thank you in advance!
- Tue Nov 19, 2019 12:40 am
- Forum: Sigma & Pi Bonds
- Topic: Symmetry of Electron Density
- Replies: 1
- Views: 228
Symmetry of Electron Density
Can someone explain the difference in the symmetry of electron density between a sigma bond and a pi bond? In lecture it was said that sigma bonds have electron densities with cylindrical symmetry around the internuclear axis, whereas pi bonds have electron densities on each side of the internuclear...
- Sun Nov 17, 2019 11:26 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Effect of electronegativity difference on bond angles
- Replies: 3
- Views: 450
Re: Effect of electronegativity difference on bond angles
In response to your question about the test, I think the test specifies which bond angle (e.g. What can you say about the bond angle between F-C-H?). In that case you'd have to specify if the bond angle is less than or greater than 109.5°.
- Sun Nov 17, 2019 11:21 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: VSEPR Notation
- Replies: 4
- Views: 377
Re: VSEPR Notation
A: central atom
X: atoms bonded to central atom
E: lone pairs
Molecules with the same formula have the same general shape (bond angles vary)
Examples:
NH3: AX3E
H2O: AX2E2
CH4 and CH3Cl: both AX4 (with tetrahedral shape)
X: atoms bonded to central atom
E: lone pairs
Molecules with the same formula have the same general shape (bond angles vary)
Examples:
NH3: AX3E
H2O: AX2E2
CH4 and CH3Cl: both AX4 (with tetrahedral shape)
- Sun Nov 17, 2019 5:45 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Test 2
- Replies: 19
- Views: 818
Re: Test 2
I think just to be safe you should draw it as accurately as you can. However if the question asks you to name the molecular shape then that should be the top priority. I hope this helps!
- Sun Nov 17, 2019 5:25 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Lone Pairs vs Bonding Pairs
- Replies: 2
- Views: 134
Lone Pairs vs Bonding Pairs
Why do lone pairs "take up" more space than bonding pairs?
- Sun Nov 17, 2019 5:16 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bonded and Lone Pairs in VSEPR
- Replies: 4
- Views: 328
Re: Bonded and Lone Pairs in VSEPR
I think lone pairs are taken into account when determining the electron distribution shape, not the molecular shape. According to my TA, the molecular shape is usually. what professor Lavelle asks for on tests.
- Sun Nov 10, 2019 8:31 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: High Distortion
- Replies: 4
- Views: 263
Re: High Distortion
MKearney_4G wrote:So would you say that electrons farther from the nucleus (higher energy) are more easily distorted?
I think you can say the electron cloud of the anion in question is more easily distorted.
- Sun Nov 10, 2019 4:18 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability Trends
- Replies: 4
- Views: 148
Re: Polarizability Trends
Also why does the high polarizability of iodine make it a solid at room temperature?
- Sun Nov 10, 2019 4:17 pm
- Forum: Polarisability of Anions, The Polarizing Power of Cations
- Topic: Polarizability Trends
- Replies: 4
- Views: 148
Polarizability Trends
Can somebody explain why heavier elements have greater polarizability? Thank you :)
- Wed Nov 06, 2019 3:12 pm
- Forum: Administrative Questions and Class Announcements
- Topic: DINO NUGGETS Review Session! Download Problems HERE [ENDORSED]
- Replies: 52
- Views: 6531
Re: DINO NUGGETS Review Session! Download Problems HERE [ENDORSED]
for mini dino nuggets 3a and 3b can someone please explain the difference between polarizing power and most polarizable? Polarizing power is used when referring to cations , which give up an electron. Polarizability refers to anions , which gain an electron. These terms both point out the covalent ...
- Wed Nov 06, 2019 4:58 am
- Forum: Administrative Questions and Class Announcements
- Topic: DINO NUGGETS Review Session! Download Problems HERE [ENDORSED]
- Replies: 52
- Views: 6531
Re: DINO NUGGETS Review Session! Download Problems HERE [ENDORSED]
In the answer key for the mini dino nuggets, the dipole moments in question 2a are going towards the negative partial charge when in the textbook it says to go towards the positive charge. What would be correct? On page 96 of the textbook it shows two. different conventions for representing the dip...
- Sun Nov 03, 2019 11:12 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Configuration Rules
- Replies: 4
- Views: 210
Re: Electron Configuration Rules
The Pauli Exclusion Principle basically states that no more than 2 electrons can occupy a single orbital. Hund's Rule states that due to electron/electron repulsion, orbitals must be occupied by one electron before they can be occupied by a second electron.
- Sun Nov 03, 2019 10:45 pm
- Forum: Trends in The Periodic Table
- Topic: Electron affinity vs electronegativity
- Replies: 7
- Views: 262
Re: Electron affinity vs electronegativity
I think it'd be best to know the definitions in your own words and to be able to identify the trends of each across the periodic table. I doubt we need to memorize the definitions word for word tho..
- Sun Nov 03, 2019 9:08 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Aufbau vs Hunds
- Replies: 6
- Views: 481
Re: Aufbau vs Hunds
Hund's Rule states that due to electron/electron repulsion, orbitals must be occupied by one electron before they can be occupied by a second electron.
The Aufbau Principle states that electrons occupy lower energy orbitals before higher energy orbitals.
The Aufbau Principle states that electrons occupy lower energy orbitals before higher energy orbitals.
- Sun Nov 03, 2019 8:57 pm
- Forum: Trends in The Periodic Table
- Topic: Does H have the highest ionization energy?
- Replies: 4
- Views: 147
Re: Does H have the highest ionization energy?
Ionization energy is defined as the energy needed to remove an electron from an atom in the gas phase. Ionization energy increases across a period and decreases down a group. For this reason, He has the highest first ionization energy.
- Sun Nov 03, 2019 8:23 pm
- Forum: Trends in The Periodic Table
- Topic: Question about the Aufbau Principle
- Replies: 1
- Views: 85
Question about the Aufbau Principle
I know that according to the Aufbau Principle, the 4s state is occupied before electrons enter the 3d state because the 4s state is lower in energy at first. But why does the 4s orbital become higher in energy once the 3d state is occupied? Thank you in advance :)
- Sun Oct 27, 2019 11:11 pm
- Forum: Trends in The Periodic Table
- Topic: Clarification about resonant molecules
- Replies: 1
- Views: 132
Clarification about resonant molecules
I wasn't sure where to post this, but why are resonant molecules more stable? Thank you in advance!
- Sun Oct 27, 2019 11:08 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Midterm
- Replies: 5
- Views: 251
Re: Midterm
For example, the shorthand electron configuration for Barium is [Xe] 6s^2. I hope this helps!
- Sun Oct 27, 2019 10:58 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Question about the Principles on Tests
- Replies: 5
- Views: 263
Question about the Principles on Tests
I was wondering if we are required to know the Pauli Exclusion Principle and Hund's Rule by name on tests?
- Sun Oct 27, 2019 10:51 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Midterm
- Replies: 5
- Views: 251
Re: Midterm
I find Khan Academy rly useful! Also YouTube videos in general go a long way for me, too. Shorthand e configuration is just the symbol of the noble gas in the previous period followed by the additional e configuration after that (got that from google).
- Sun Oct 27, 2019 10:45 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Midterm
- Replies: 5
- Views: 251
Re: Midterm
I think we should just to be sure, since there's problems about it in the homework and it was talked about in discussion. :)
- Sun Oct 20, 2019 11:35 pm
- Forum: Properties of Light
- Topic: Next test
- Replies: 23
- Views: 1030
Re: Next test
Yeah it's the same sheet that can be found on the website. However, my TA said there are some equations that aren't found on the sheet (?) so...
- Sun Oct 20, 2019 11:28 pm
- Forum: Significant Figures
- Topic: %Mass Composition
- Replies: 12
- Views: 716
Re: %Mass Composition
The number of sig figs you keep always depends on the lowest amount of sig figs used in the question. For ex., if the question uses the numbers 7.0g, 3g,and 0.003004g, your answer should use one sig fig, because its dependent on 3g.
- Sun Oct 20, 2019 11:22 pm
- Forum: SI Units, Unit Conversions
- Topic: Accuracy vs Precision
- Replies: 11
- Views: 739
Re: Accuracy vs Precision
Accuracy is the proximity of your value to the actual value. Precision is the closeness of all your values. Your value is more accurate if its closer to the actual value. Your values are precise if they're all relatively close to each other.
- Sun Oct 20, 2019 11:17 pm
- Forum: Significant Figures
- Topic: Sig Figs at the Beginning or End
- Replies: 14
- Views: 4694
Re: Sig Figs at the Beginning or End
It's best to apply the sig fig rules at the end of all calculations so you get the most accurate answer :)