Search found 48 matches
- Sat Mar 17, 2018 9:12 pm
- Forum: Method of Initial Rates (To Determine n and k)
- Topic: Determining Which Experiments
- Replies: 2
- Views: 403
Re: Determining Which Experiments
You want to control the concentration of the reactant you are determining the order of, so you would compare the two experiments in which only that reactant's concentration differs. Hope this helps! (-:
- Tue Mar 13, 2018 11:40 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: 15.101b)
- Replies: 1
- Views: 266
Re: 15.101b)
I believe this is in our notes, but it states that H20, H30+, and OH- can be present in the rate law if they are part of the reaction mechanism (although we end to omit water because it's concentration is so much higher). I don't think it's an intermediate because it has a fixed, long-term presence ...
- Tue Mar 13, 2018 11:23 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: catalysts
- Replies: 5
- Views: 685
Re: catalysts
Catalysts don't show up when writing the overall reaction, and aren't included in the rate law either. However, they indirectly change the k value of the rate law by lowering the activation energy of the reaction.
- Tue Mar 13, 2018 11:07 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: arrhenius equation
- Replies: 3
- Views: 408
Re: arrhenius equation
There's a recent post that discusses the Arrhenius equation as well. Here's the link
viewtopic.php?f=151&t=29213
viewtopic.php?f=151&t=29213
- Sun Mar 11, 2018 4:40 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Dimerization
- Replies: 2
- Views: 361
Re: Dimerization
I believe dimerization is just when 2 molecules of the same composition react with each other! so an example of this would be something like A + A → A2
- Sun Mar 11, 2018 4:31 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: HW 15.95
- Replies: 2
- Views: 351
Re: HW 15.95
I believe it's 2 because looking at the graph, there are two lower points in between each step of the reaction. Page 652 in the textbook shows this on the graphs in the top left corner
- Thu Mar 08, 2018 1:14 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Arrhenius Equation [ENDORSED]
- Replies: 7
- Views: 843
Re: Arrhenius Equation [ENDORSED]
You can use the Arrhenius equation to show the effect a change of temperature has on the rate constant (and thus the reaction as well). Hope this helps!
- Sun Mar 04, 2018 11:52 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: 15.69
- Replies: 2
- Views: 328
Re: 15.69
Joshua is right! 15.69 shouldn't be on our test this week, and I don't believe we've covered it in any lectures yet, so I wouldn't really worry about this until we cover it in class
- Sun Mar 04, 2018 11:40 pm
- Forum: Zero Order Reactions
- Topic: Identifying zero order
- Replies: 6
- Views: 925
Re: Identifying zero order
you might also find this helpful for additional info!
https://chem.libretexts.org/Core/Physic ... _Reactions
https://chem.libretexts.org/Core/Physic ... _Reactions
- Fri Mar 02, 2018 6:39 am
- Forum: Administrative Questions and Class Announcements
- Topic: Test 3
- Replies: 6
- Views: 862
Re: Test 3
the other post about test 3 recommended going up to #43, so just to be safe I would include those for extra practice!
- Fri Feb 23, 2018 3:50 am
- Forum: Balancing Redox Reactions
- Topic: 14.13c
- Replies: 2
- Views: 400
Re: 14.13c
I believe that's right as well; it's probably more commonly written as Cl2(g)|Cl-(g) because it makes a little more sense in conveying the reaction occurring, but it doesn't really matter as long as they're both on the anode side
- Fri Feb 23, 2018 3:46 am
- Forum: Balancing Redox Reactions
- Topic: 14.5a
- Replies: 2
- Views: 417
Re: 14.5a
I agree! I believe it's a solution manual error, so I wouldn't worry about it too much.
- Sun Feb 18, 2018 11:59 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Quiz 2
- Replies: 1
- Views: 340
Re: Quiz 2
Yeah, I believe this test will follow a similar format where you should understand both concepts and applications
- Wed Feb 14, 2018 3:49 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: q==q
- Replies: 2
- Views: 422
Re: q==q
it matters; the question is focusing on the copper cube, so the copper cube is the system and would be the positive q. it also depends on the direction the energy is flowing, so since the surroundings are losing energy to the copper cube (which is absorbing energy), q for surroundings would be negat...
- Wed Feb 14, 2018 3:43 am
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Equation
- Replies: 2
- Views: 567
Re: Van't Hoff Equation
there's a possibility it could show up on the test so I'd know/understand it just in case!
- Wed Feb 14, 2018 3:41 am
- Forum: Student Social/Study Group
- Topic: Midterm Equations
- Replies: 1
- Views: 467
Re: Midterm Equations
I believe we'll be supplied with all the equations we'll need for the midterm! I also heard we won't need to do any derivations, however it'd still be really helpful to understand them and know when to use them. I don't think the Van't Hoff equation is included on the sheet, but that one is pretty s...
- Fri Feb 09, 2018 1:28 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Finding entropy of vaporization from temperatures NOT = to boiling point [ENDORSED]
- Replies: 3
- Views: 1146
Re: Finding entropy of vaporization from temperatures NOT = to boiling point [ENDORSED]
Is this for problem 9.19? I believe you do so because the problem is asking for the entropy when the vaporized water is 85 degrees celsius (as the final temperature), therefore you have to cool the water after you change its state by vaporization. Hope that makes sense!
- Fri Feb 09, 2018 1:19 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode and cathode
- Replies: 9
- Views: 1361
Re: Anode and cathode
Additionally, electrons always flow out of the anode and into the cathode
- Fri Feb 09, 2018 12:38 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Exercise 9.19
- Replies: 2
- Views: 433
Re: Exercise 9.19
Was it a typo that you said 83 degrees? I agree with Tanaisha; you'll have to change the state of the water by heating it up, then you bring the temperature back down to the desired temp in the problem!
- Fri Feb 02, 2018 6:57 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: bond enthalpy [ENDORSED]
- Replies: 4
- Views: 570
Re: bond enthalpy [ENDORSED]
I agree! If polarity does play any roles in determining bond enthalpy, I'm pretty sure it's a negligible effect.
- Fri Feb 02, 2018 5:40 am
- Forum: Phase Changes & Related Calculations
- Topic: Adding Delta H(Fusion/Vaporization )
- Replies: 2
- Views: 529
Re: Adding Delta H(Fusion/Vaporization )
You add delta H fusion/vaporization because the enthalpy of the objects are different values when they are in different states, so you have to include that specific change in energy when calculating the total, if that makes sense! (for example, if you look at it in terms of water's heat curve, you c...
- Thu Feb 01, 2018 1:02 am
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Midterm
- Replies: 6
- Views: 718
Re: Midterm
I agree. For the majority of his tests, a majority of points come from calculations/problem-solving, however it will definitely require an understanding of the concepts, so it would definitely be helpful to study both!
- Tue Jan 23, 2018 10:50 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: system of vacuum
- Replies: 4
- Views: 569
Re: system of vacuum
I believe so! Since there is no transfer of heat or mass, the contents of the vacuum would be isolated.
- Tue Jan 23, 2018 10:46 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Temperature
- Replies: 3
- Views: 291
Re: Temperature
I think it's best to keep your answer in Kelvin since it's the standard unit for Gibbs Free Energy! I'm not entirely sure if the reason is so that it's a positive value, but it makes sense to me. Hopefully someone can clarify that part
- Tue Jan 23, 2018 10:37 am
- Forum: Administrative Questions and Class Announcements
- Topic: Week 3 Test Topic is endorsed
- Replies: 37
- Views: 4738
Re: Week 3 Test Topic is endorsed
how similar are the homework questions to lavelle's test questions? Dr. Lavelle usually includes a homework problem or one that is very similar to the homework in his tests, so it can be pretty similar. In general I find it really helpful to do the homework! If anything, sometimes the homework can ...
- Tue Jan 23, 2018 10:31 am
- Forum: Administrative Questions and Class Announcements
- Topic: Week 3 Test Topic is endorsed
- Replies: 37
- Views: 4738
Re: Week 3 Test Topic is endorsed
Warda Sahib 2E wrote:Does Dr. Lavelle only test on things he's talked about?
For the most part, Dr. Lavelle covers everything we should know for the test conceptually with some examples, but it's definitely recommended to prepare by doing the homework while also reviewing notes!
- Sat Jan 20, 2018 3:56 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Pressure
- Replies: 2
- Views: 150
Re: Pressure
Can you please clarify which concept this is from? Your reasoning sounds correct, but I'm not sure which equation/concept you are referring to about the cooling and I couldn't find it in my notes. Thanks!
- Sat Jan 20, 2018 3:48 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Work Equation
- Replies: 4
- Views: 500
Re: Work Equation
Payton Schwesinger 1J wrote:I also think that if the system is doing work on the surroundings, then energy is being released and therefore the work has a negative value... am I thinking about this right?
Yes, that's also right!
- Sat Jan 20, 2018 4:14 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Thermochemical equation
- Replies: 5
- Views: 764
Re: Thermochemical equation
I believe it is because there are 2 moles of C6H6, and so in order to find the change in enthalpy you must multiply by 2. I think the book explains this a little more at the top of page 289 if that helps!
- Sat Jan 20, 2018 4:02 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2969716
- Sat Jan 20, 2018 4:00 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 2969716
- Sat Jan 20, 2018 3:53 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Problem 8.65
- Replies: 3
- Views: 385
Re: Problem 8.65
I agree with Juanyi! These problems ask for the exact equation, so even though it might make more sense or be easier to use whole numbers, you have to convert it according to the given equation
- Sat Jan 20, 2018 3:51 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: 8.37
- Replies: 3
- Views: 302
Re: 8.37
I don't think it really matters since it's the same quantity, but to be safe I would put it in the units given in the problem, which is moles for #37. Hopefully someone else can clarify as well!
- Fri Dec 08, 2017 11:28 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: X in ICE table
- Replies: 3
- Views: 505
Re: X in ICE table
We can consider x negligible if it if the value of Kc is less than 10^-7. In this case, you can omit the "-x" but still leave it in the product (ex. Kc=(2x)/(1-x)(4-x) could be rewritten as (2x)/(1)(4) if Kc is less than 10^-7). You can also note that if there's ever a cubic situation, you...
- Fri Dec 08, 2017 11:22 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Kc vs Kp
- Replies: 3
- Views: 281
Re: Kc vs Kp
At least for the practice final, K referred to Kc, so I think unless otherwise stated it will be Kc. Hopefully someone else can confirm
- Sun Nov 26, 2017 10:03 pm
- Forum: Hybridization
- Topic: HMK 4.91
- Replies: 3
- Views: 505
Re: HMK 4.91
I could be mistaken but I think it's the opposite actually: the two sp hybridized carbon atoms are in a more constrained position since it's in a six-figure chain (at 120 degree angle), instead of the arrangement it would normally have, which is linear (with a 180 degree angle). Therefore, it's more...
- Sun Nov 26, 2017 9:53 pm
- Forum: Naming
- Topic: test 4 [ENDORSED]
- Replies: 4
- Views: 459
Re: test 4 [ENDORSED]
Yes I believe so, since Test 4 is supposed to cover Ch. 4, 17, and Ch. 11.1 to the end of 11.8, and coordination compounds are covered all in Ch. 17.
Hope this helps!
Hope this helps!
- Fri Nov 17, 2017 3:45 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm on myucla
- Replies: 6
- Views: 804
Re: Midterm on myucla
Just for clarification, on the syllabus it says that "only at the end of the class when the class average score (out of 500 points) is known are final grades assigned."
So does this mean that the class is curved at the end of the quarter?
So does this mean that the class is curved at the end of the quarter?
- Thu Nov 16, 2017 4:21 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Exercise 4.7 and 4.9
- Replies: 2
- Views: 247
Re: Exercise 4.7 and 4.9
Yeah, it has to do with electron repulsion! Since there are 2 lone pairs on Iodine in ICl3, the electron repulsions balance each other out so the shape remains T-shaped, as opposed to how Sulfur in SOCl2 has a single lone pair that repels the bonded electron pairs.
- Thu Nov 09, 2017 2:28 am
- Forum: Lewis Structures
- Topic: N2O LEWISH STRUCTURE
- Replies: 3
- Views: 994
Re: N2O LEWISH STRUCTURE
There are 3 different ways to draw the Lewis structure for N2O: 1. N with 3 lone pr, 1 bonding pr to N with 3 bonding pr to O with 1 lone pr 2. N with 2 lone pr, 2 bonding pr to N with 2 bonding pr to O with 2 lone pr 3. N with 1 lone pr, 3 bonding pr to N with 1 bonding pr to O with 3 lone pr The t...
- Mon Nov 06, 2017 11:33 pm
- Forum: Ionic & Covalent Bonds
- Topic: Electron Configuration and d-block (3.11)
- Replies: 2
- Views: 390
Electron Configuration and d-block (3.11)
Hi everyone, I am confused on understanding the electron configuration of certain elements in the d-block. I had thought the only exceptions were Cu, Cr, and Ag, and everything else continued with the trend of filling the s-block then d-block. But, for example, Ruthenium has the configuration [Kr] 4...
- Sat Oct 28, 2017 10:36 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: 2.85
- Replies: 5
- Views: 481
Re: 2.85
Additionally from a previous Chemistry Community post: "As the occupied energy levels increase in principal quantum number, the energies get closer and closer together to the point that their energy DEPENDS on how many electrons in that level. This does not happen until the transition metals, w...
- Fri Oct 27, 2017 5:07 pm
- Forum: Ionic & Covalent Bonds
- Topic: Cations and Anions [ENDORSED]
- Replies: 12
- Views: 2095
Re: Cations and Anions [ENDORSED]
https://www.youtube.com/watch?v=6OxRB9ShoHw
This is a video with a general description of ions.
https://www.youtube.com/watch?v=zTUnjPALX_U
This is another video that goes more in-depth with ions.
Hopefully these are helpful in determining the difference between the two!
This is a video with a general description of ions.
https://www.youtube.com/watch?v=zTUnjPALX_U
This is another video that goes more in-depth with ions.
Hopefully these are helpful in determining the difference between the two!
- Mon Oct 16, 2017 3:13 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Homework Problem 1.15
- Replies: 4
- Views: 548
Homework Problem 1.15
Hi everyone, I don't think I am understanding the concept of En=-(hR)/(n^2). In the homework set problem 1.15, I started by solving for the frequency using the given wavelength (102.6 nm), then using the frequency to solve for the energy, and now I'm stuck. I'm comparing my work to the solutions man...
- Thu Oct 12, 2017 2:10 am
- Forum: Properties of Light
- Topic: HW Problem 1.3
- Replies: 4
- Views: 588
Re: HW Problem 1.3
My book said that the electrical field corresponds to the amplitude of the wavelength, so when the frequency is decreased the waves flatten out, thus decreasing the slope (extent of change) of the wave too. Hope this helps!
- Thu Oct 12, 2017 2:06 am
- Forum: Photoelectric Effect
- Topic: Problem 1.7 HW
- Replies: 4
- Views: 536
Re: Problem 1.7 HW
I think it's a typo. I solved the problem as wavelength = (c/v) = ((2.998E8 m/s)/(2.0E18 Hz)) and also got 150 pm.
- Thu Oct 05, 2017 8:27 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: G17
- Replies: 2
- Views: 388
Re: G17
Technically you only need to round to 2 sig figs at the end since that's how many are given in the problem, but when you're converting from moles to grams or vice versa or doing other calculations you should use the full numbers given to you on the periodic table. I'm sure someone else can confirm f...
- Thu Oct 05, 2017 8:18 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Molarity and Dilution [ENDORSED]
- Replies: 7
- Views: 2105
Re: Molarity and Dilution [ENDORSED]
You can still use the Molarity = mol/vol equation, the question is just worded in an unusual way. I could be wrong, but in summary I think the problem was just stating that 55.1g of KCl is added to 125 mL of water.