Search found 102 matches
- Fri Mar 12, 2021 11:22 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Sapling Week 9/10 Question #7
- Replies: 5
- Views: 460
Re: Sapling Week 9/10 Question #7
Once you compute the order of each reactant, the rate is equal to k multiplied by the concentration of each reactant to the power of its order. So it would look like rate = k([A]^l)([B]^m)([C]^n) are the l, m, and n the order of the reactants? yes! l is the order for reactant A, m --> B, n --> C
- Fri Mar 12, 2021 11:13 pm
- Forum: Zero Order Reactions
- Topic: Sapling Question week 9/10
- Replies: 18
- Views: 4158
Re: Sapling Question week 9/10
Part 5 isn't asking for a numerical value. You use the order for each reactant (found in parts 1,2,3) to find the rate law for this reaction: rate = k [A]^n [B]^m [C]^l. (A zero-order reactant just becomes a 1 in the rate law.) Using this equation, you can use the rate and concentrations from any o...
- Fri Mar 12, 2021 11:04 pm
- Forum: First Order Reactions
- Topic: Focus Exercise 7.27
- Replies: 2
- Views: 307
Re: Focus Exercise 7.27
Hi! First, I plugged the 4.5 into the 1st order half-life equation to find the value of k. Then you can find the value of [A]naught by dividing mass of phenobarbitol by the mass of the dog. Plug these values into the equation for a 1st order reaction to find ln [A] for time=2hrs. Use stoichiometry t...
- Fri Mar 12, 2021 10:53 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: Sapling Week 9/10 Question #7
- Replies: 5
- Views: 460
Re: Sapling Week 9/10 Question #7
Once you compute the order of each reactant, the rate is equal to k multiplied by the concentration of each reactant to the power of its order.
So it would look like rate = k([A]^l)([B]^m)([C]^n)
So it would look like rate = k([A]^l)([B]^m)([C]^n)
- Thu Mar 11, 2021 4:09 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook 6M.1
- Replies: 2
- Views: 213
Re: Textbook 6M.1
For this one, you should refer the the appendix for the list of standard reduction potentials.
- Thu Mar 11, 2021 4:06 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Sapling #17
- Replies: 3
- Views: 242
Re: Sapling #17
It helps a lot to draw out the reaction profile! Since deltaH is positive, the reaction is endothermic, and deltaH is the energy difference between the reactants and the products. The activation energy given is for the forward reaction, and you will see that the activation energy for the reverse is ...
- Thu Mar 11, 2021 3:58 pm
- Forum: Student Social/Study Group
- Topic: How are y'all doing?
- Replies: 46
- Views: 3509
Re: How are y'all doing?
There is so much to do this week but being productive is so hard. But I'm keeping myself going by reminding myself that I just have to get through this last week and then I can actually enjoy my free time.
- Thu Mar 11, 2021 3:51 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Sapling #14
- Replies: 4
- Views: 310
Re: Sapling #14
If you press "Hint", Sapling gives a useful version of the Vant Hoff equation. Changing the temperature only affects the k value, so you are looking for a value T2, which makes the ratio of k2/k1 equal to 3.
- Sun Mar 07, 2021 3:54 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell diagram but no phases given
- Replies: 1
- Views: 207
Re: Cell diagram but no phases given
You can identify the oxidization and reduction half-reactions by comparing the reduction potentials for each. Since the Ti reaction involves 2 ions, you will need to add Pt on that side.
- Sun Mar 07, 2021 3:47 am
- Forum: Balancing Redox Reactions
- Topic: Half-Reactions
- Replies: 11
- Views: 681
Re: Half-Reactions
We probably will be asked to figure out half-reactions by ourselves because most of one section of the textbook exercises asks us to write out the two half-reactions in order to find the balanced equation.
- Sun Mar 07, 2021 3:43 am
- Forum: Student Social/Study Group
- Topic: Spring Break
- Replies: 53
- Views: 4617
Re: Spring Break
I'm gonna sleep a lot and binge some shows I've been wanting to watch since first round of midterms.
- Sun Mar 07, 2021 3:42 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Sapling Question week 9/10
- Replies: 5
- Views: 3419
Re: Sapling Question week 9/10
Since this is a first order reaction, use the 1st order integrated rate law: ln[A] = -kt + ln[A]naught
Isolate t and plug in all of the given values. This gives you the answer in seconds, so divide by 60.
Isolate t and plug in all of the given values. This gives you the answer in seconds, so divide by 60.
- Sun Mar 07, 2021 3:31 am
- Forum: Zero Order Reactions
- Topic: Sapling Question week 9/10
- Replies: 18
- Views: 4158
Re: Sapling Question week 9/10
Part 5 isn't asking for a numerical value. You use the order for each reactant (found in parts 1,2,3) to find the rate law for this reaction: rate = k [A]^n [B]^m [C]^l. (A zero-order reactant just becomes a 1 in the rate law.) Using this equation, you can use the rate and concentrations from any of...
- Sun Feb 28, 2021 12:20 am
- Forum: Student Social/Study Group
- Topic: Final Jitters
- Replies: 457
- Views: 495264
Re: Final Jitters
Make sure you are preparing far in advance! The worst thing before an exam is feeling like you haven't studied enough, and that almost always makes me perform worse.
- Sun Feb 28, 2021 12:14 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Direction of ion flow in Galvanic cells
- Replies: 6
- Views: 2735
Re: Direction of ion flow in Galvanic cells
I believe anions flow from the right to the left, and cations have to flow from the left to the right since the oxidized form of the cathode metal carries a positive charge and enters the solution during the reaction.
- Sun Feb 28, 2021 12:12 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode/Cathode in Concentration Cells
- Replies: 5
- Views: 599
Re: Anode/Cathode in Concentration Cells
I believe that Professor Lavelle said that in diagrams the cathode would always be on the right because electrons always flow left to right. If you wanted to make sure, the electrode that is losing material into the solution is the anode, and the electrode gaining material is the cathode.
- Sun Feb 28, 2021 12:06 am
- Forum: Student Social/Study Group
- Topic: Chem 14B Final
- Replies: 86
- Views: 8025
Re: Chem 14B Final
Go to practice sessions and make sure you're really good with the content we spent a lot of time learning!!
- Sat Feb 27, 2021 11:59 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: E Cell
- Replies: 5
- Views: 408
Re: E Cell
E naught represents the cell potential at standard conditions, while Ecell is the cell potential at non-standard conditions, which someone gave the equation to find above.
- Sun Feb 21, 2021 5:46 pm
- Forum: Balancing Redox Reactions
- Topic: Standard Reduction Potential
- Replies: 1
- Views: 161
Re: Standard Reduction Potential
They should be; I don't think Professor Lavelle would expect us to memorize any E° values.
- Sun Feb 21, 2021 5:45 pm
- Forum: Student Social/Study Group
- Topic: We made it through Midterm 2!
- Replies: 71
- Views: 5949
Re: We made it through Midterm 2!
Thermodynamics was really tough, but I am glad to have gotten through that midterm and to be able to destress for like a week.
- Sun Feb 21, 2021 5:40 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Sapling #6
- Replies: 5
- Views: 437
Re: Sapling #6
In a setup like that, I believe the anode will always be in the left beaker, and electrons always flow left to right.
- Sun Feb 21, 2021 5:32 pm
- Forum: Balancing Redox Reactions
- Topic: oxidizing agent
- Replies: 3
- Views: 257
Re: oxidizing agent
Hi! Refer to the table of standard reduction potentials (linked if you click Hint). Professor Lavelle said in class that the half reaction with the lower standard reduction potential will be reversed, and this will end up being the oxidation reaction.
- Sun Feb 21, 2021 5:28 pm
- Forum: Balancing Redox Reactions
- Topic: Anode and Cathode
- Replies: 11
- Views: 606
Re: Anode and Cathode
Yes, the cathode has a more positive charge, so electrons will flow to the right, and the reaction on the right will always be a reduction.
- Sun Feb 21, 2021 5:27 pm
- Forum: Student Social/Study Group
- Topic: Post Midterm 2 De-stressing
- Replies: 92
- Views: 10425
Re: Post Midterm 2 De-stressing
I've been eating ramen and watching youtube and my weekend has been very nice so far<3
- Mon Feb 15, 2021 12:59 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Meaning of K
- Replies: 55
- Views: 4628
Re: Meaning of K
Yes, in all of the equations Professor Lavelle has given us with a capital K, the K is the equilibrium constant.
- Mon Feb 15, 2021 12:43 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Reversible vs Irreversible
- Replies: 4
- Views: 304
Re: Reversible vs Irreversible
If a system is acting against a constant external pressure, the reaction is irreversible. I think the problem would most likely tell you if you had to find work for an irreversible reaction since they do not occur in the real world. The equation for work for an irreversible reaction is w = -PΔV. The...
- Mon Feb 15, 2021 12:27 am
- Forum: Van't Hoff Equation
- Topic: Van't Hoff Equation
- Replies: 5
- Views: 329
Re: Van't Hoff Equation
I would say it's not necessary to know how to derive the equation since exams are multiple choice.
- Sun Feb 07, 2021 9:50 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Negative Sign
- Replies: 16
- Views: 727
Re: Negative Sign
If you have q(system) = q(surroundings), I believe it depends on if the reaction is exothermic or endothermic. If it is exothermic, q(sys) is negative because the system releases heat into the surroundings.
- Sun Feb 07, 2021 3:11 pm
- Forum: Student Social/Study Group
- Topic: Spring 2021
- Replies: 106
- Views: 27366
Re: Spring 2021
I'm taking it next quarter hopefully along with LS7B and 14C.
- Sun Feb 07, 2021 3:05 pm
- Forum: Student Social/Study Group
- Topic: Studying When You Don't Want to
- Replies: 48
- Views: 4164
Re: Studying When You Don't Want to
I know this feeling so well, and lately I've been trying to set timers for myself to make sure I am productive for some period of time, and giving myself breaks frequently. It worked pretty well when I was preparing for midterms!!
- Sun Feb 07, 2021 6:03 am
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Entropy vs Enthalpy
- Replies: 11
- Views: 616
Re: Entropy vs Enthalpy
Enthalpy is the total energy in a system, and entropy is a measure of disorder. One thing that helped me understand entropy is the more ways things can be arranged, the higher the entropy. For example, 1 glucose molecule has lower entropy than 6 CO2 and 6 H2O.
- Sun Feb 07, 2021 5:59 am
- Forum: Phase Changes & Related Calculations
- Topic: Boiling water
- Replies: 25
- Views: 3288
Re: Boiling water
It is because water forms so many hydrogen bonds, which are a relatively strong intermolecular force (compared to something like dispersion forces). When water reaches its boiling point and is being converted to a gas, the energy is being used to break the hydrogen bonds in the water so that the wat...
- Sun Feb 07, 2021 5:55 am
- Forum: General Science Questions
- Topic: Careless Mistakes
- Replies: 54
- Views: 4709
Re: Careless Mistakes
For this all I can really say is writing out your work clearly and including units. Also double checking often.
- Mon Feb 01, 2021 12:53 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Reaction enthalpies and bond enthalpies
- Replies: 4
- Views: 284
Re: Reaction enthalpies and bond enthalpies
All three examples that we went over in class allow you to find the change in enthalpy for a given reaction. However (I'm not sure if you had this problem on the MT), you could also find a certain bond enthalpy using the 2nd method if you are given the right information.
- Mon Feb 01, 2021 12:48 am
- Forum: General Science Questions
- Topic: Midterm 1 Reactions
- Replies: 70
- Views: 7187
Re: Midterm 1 Reactions
I think I prepared as much as I could have for the exam but my nerves really got to me. Overall it was mostly what I expected though.
- Sun Jan 31, 2021 6:18 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Heat capacity vs Specific heat in Calorimetry
- Replies: 5
- Views: 298
Re: Heat capacity vs Specific heat in Calorimetry
I believe heat capacity is referring to the heat required to raise the temperature of an object of any mass by 1 degree C, and has the units kJ.K^-1. To get specific heat capacity from heat capacity, you would divide the heat capacity by the # grams of substance present. This gives you the units kJ....
- Sun Jan 31, 2021 5:43 pm
- Forum: Ideal Gases
- Topic: Chem BL
- Replies: 107
- Views: 12957
Re: Chem BL
I'm hoping to take it next quarter with 14C but I'm a little worried because I heard enrollment is pretty competitive.
- Sun Jan 31, 2021 5:39 pm
- Forum: Student Social/Study Group
- Topic: Go treat yourself after MT1!
- Replies: 75
- Views: 8339
Re: Go treat yourself after MT1!
treating myself by binging netflix for the entire weekend woooo
- Sun Jan 24, 2021 4:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook Problem 5.35
- Replies: 1
- Views: 173
Re: Textbook Problem 5.35
I believe they're converting kPa to atm because that is what the formula for K requires. 1 atm is 101.325 kPa.
- Sun Jan 24, 2021 4:19 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook Question 5I.15
- Replies: 2
- Views: 249
Re: Textbook Question 5I.15
I think that they gave us the concentration of NH4HS so we could recognize the fact that it has no effect on the equilibrium constant. And I believe we would still use +x for all of the products because it is always true that if x of one product is formed, then x of the other product is formed. The ...
- Sun Jan 24, 2021 4:01 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook Problem 5I.13
- Replies: 1
- Views: 171
Re: Textbook Problem 5I.13
Actually I believe the answer key did use the value for 1000 K. Make sure you're looking at the equilibrium constant for gases!
- Sun Jan 24, 2021 3:49 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm Timing
- Replies: 15
- Views: 708
Re: Midterm Timing
I think that if you've done a lot of practice with the calculations then you should be fine with time.
- Sun Jan 24, 2021 3:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: How to find the H+ from pH
- Replies: 12
- Views: 613
Re: How to find the H+ from pH
It's 10^(-pH).
- Sat Jan 16, 2021 5:15 pm
- Forum: Student Social/Study Group
- Topic: Number of Chemistry Community Posts
- Replies: 45
- Views: 3034
Re: Number of Chemistry Community Posts
For 14A we only needed 50 by the end of the quarter, so I think if you have 100 by the end of the quarter it should be fine. I don't think the TA's keep track of how many posts we started with.
- Sat Jan 16, 2021 5:12 pm
- Forum: Student Social/Study Group
- Topic: Study Habits
- Replies: 96
- Views: 9856
Re: Study Habits
I set study goals for myself every day in order to avoid having to cram everything before exams.
- Sat Jan 16, 2021 5:06 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: sapling homework #2
- Replies: 5
- Views: 357
Re: sapling homework #2
From the information given, you can compute the equilibrium concentration of O2. Using stoichiometry, you can also get the equilibrium concentration of SO2 (2 moles of SO2 produced per 1 mole of O2) and the equilibrium concentration of SO3 (2 moles of SO3 consumed for every mole of O2 produced, and ...
- Sat Jan 16, 2021 5:00 pm
- Forum: Student Social/Study Group
- Topic: Comfort Movies
- Replies: 168
- Views: 50960
Re: Comfort Movies
I just watched Mulan last night for probably like the 50th time!!
- Sat Jan 09, 2021 7:27 pm
- Forum: Student Social/Study Group
- Topic: New Year Resolutions?
- Replies: 54
- Views: 4233
Re: New Year Resolutions?
I want a regular sleep schedule and to move around more.
- Sat Jan 09, 2021 6:54 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5H 1b
- Replies: 3
- Views: 208
Re: 5H 1b
I remembering seeing fractions as coefficients in my high school chemistry class so I think it's still correct. I assume you would plug everything into the equation the same way, or you could make all of the coefficients whole numbers.
- Sat Jan 09, 2021 6:49 pm
- Forum: Student Social/Study Group
- Topic: How to relax
- Replies: 168
- Views: 47269
Re: How to relax
Warm drinks and netflix are my favorite!!
- Sat Jan 09, 2021 4:43 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Lecture 3 Inert Gas
- Replies: 5
- Views: 250
Re: Lecture 3 Inert Gas
increase/decrease of pressure does not necessarily mean the volume changes. Changing the volume of a (gaseous) solution is just one way to change its pressure.
- Sat Jan 09, 2021 4:39 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Conceptual Understanding of Decrease in Volume
- Replies: 3
- Views: 157
Re: Conceptual Understanding of Decrease in Volume
When the pressure of a gas changes (because its volume changes), the K value stays the same for that reaction. However, the concentration of the solution changes because c = n/v. When you put the new concentration values into the equation Q = [P]/[R], you see that the reaction quotient Q is unequal ...
- Tue Dec 15, 2020 3:22 am
- Forum: Student Social/Study Group
- Topic: Final Exam
- Replies: 49
- Views: 3469
Re: Final Exam
This exam definitely did feel more rushed than the midterms :// For both midterms I had time to go over all of my answers with time left and I ended up submitting this final in the last 10 seconds.
- Sun Dec 13, 2020 12:27 am
- Forum: Student Social/Study Group
- Topic: Grades
- Replies: 29
- Views: 1711
Re: Grades
Not sure about the grade, but Professor Lavelle sent an email out today saying we have until Tuesday 9am to get our 50 posts. Also, Chem community will be closed to posts from 11:30am to 10:30pm today during finals.
Re: "ferrate"
I believe ferrate is only used when the coordination compound has an overall negative charge; otherwise you can just use iron. I also didn't know about this until I did the textbook problems so I'm not sure if this will show up on the exam. And from what I know, there are a few other similar excepti...
- Sat Dec 12, 2020 9:33 pm
- Forum: Naming
- Topic: K[Cu(en)2 (CN)2 ]
- Replies: 7
- Views: 642
Re: K[Cu(en)2 (CN)2 ]
You can look at this entire compound as an ionic compound, where K+ is the cation and the coordination compound is the anion. Since the whole compound is neutral, the coordination compound must have a charge of -1. So, since each CN has a charge of -1, Cu has a charge of +1.
- Sat Dec 12, 2020 9:30 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 490
- Views: 714124
Re: Saying Thank You to Dr. Lavelle
Hi Dr. Lavelle!!
I genuinely enjoyed your lectures so much and wish so badly I could have taken this class in person. I am so grateful for all the resources you set up for us, as well as the TAs and UAs who worked so hard, and I am looking forward to 14B next quarter!!
I genuinely enjoyed your lectures so much and wish so badly I could have taken this class in person. I am so grateful for all the resources you set up for us, as well as the TAs and UAs who worked so hard, and I am looking forward to 14B next quarter!!
- Sat Dec 05, 2020 11:50 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: coordination number
- Replies: 13
- Views: 904
Re: coordination number
You can get the coordination number by looking at how many atoms/compunds are inside the brackets (aside from the transition metal), because those are directly bonded to the transition metal.
- Sat Dec 05, 2020 11:40 pm
- Forum: Student Social/Study Group
- Topic: How are you?
- Replies: 154
- Views: 21751
Re: How are you?
a bit stressed, very tired of being in my house but overall okay thank you for asking!!
- Sat Dec 05, 2020 11:38 pm
- Forum: Student Social/Study Group
- Topic: Evaluations
- Replies: 17
- Views: 1127
Re: Evaluations
Don't think Dr. Lavelle ever mentioned anything like that, so probably not, but it would be very nice.
- Sat Dec 05, 2020 11:28 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final
- Replies: 21
- Views: 1015
Re: Final
Yes, I think proctoring is the same, but the exam is 30 questions, 6 pts each.
- Sat Dec 05, 2020 11:24 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Sapling W9 #3
- Replies: 6
- Views: 418
Re: Sapling W9 #3
With 6 bonds, a planar structure would never be ideal because the regions of electron density want to be as far from each other as possible.
- Sun Nov 29, 2020 6:37 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: H20 Shape
- Replies: 17
- Views: 1190
Re: H20 Shape
Try to visualize an H2O molecule in 3D. The regions of e- density want to be as far from each other as possible, and have a square planar configuration with only 4 regions of e- density leaves 2 sides of the central atom empty. Professor Lavelle showed us a representation of what an atom with a tetr...
- Sun Nov 29, 2020 6:32 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Two lone pairs shape
- Replies: 2
- Views: 173
Re: Two lone pairs shape
If you look at the two models, you will see that the first one has 6 regions of electron density (with 2 lone pairs) while the second one only has 5 regions of electron density (with 1 lone pair). :)
- Sun Nov 29, 2020 6:28 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Cyclic Structures
- Replies: 3
- Views: 232
Re: Cyclic Structures
When looking for a cyclic structure, I would just start by forming a simple ring (in this case, a triangle) with the carbons and adding all of the hydrogens after. Then, add bonds wherever necessary so that each carbon has 4 bonds.
- Sun Nov 29, 2020 6:22 pm
- Forum: Dipole Moments
- Topic: Tetrahedral Atoms and Dipole Moments
- Replies: 7
- Views: 534
Re: Tetrahedral Atoms and Dipole Moments
Yes, because the tetrahedral shape makes it impossible for all of the dipoles to cancel out unless all 4 are the same magnitude.
- Sun Nov 29, 2020 6:10 pm
- Forum: Ionic & Covalent Bonds
- Topic: Lewis structure
- Replies: 13
- Views: 794
Re: Lewis structure
I believe you can only tell if something can be an acid or base by looking at the Lewis structure. A base has an extra lone pair and an acid can accept a lone pair because it is electron deficient (ex. H+ ion or BF3). As for covalent vs. ionic, you would have to have an idea of their relative electr...
- Sun Nov 29, 2020 1:59 am
- Forum: Student Social/Study Group
- Topic: Sampling Give Up Option
- Replies: 12
- Views: 673
Re: Sampling Give Up Option
Yes, you will lose points.
- Sun Nov 22, 2020 4:58 pm
- Forum: Ionic & Covalent Bonds
- Topic: Covalent Character
- Replies: 33
- Views: 1919
Re: Covalent Character
Yes, all you really have to look at is the electronegativity difference between the two bonded atoms. The smaller the difference, the more covalent character.
- Sun Nov 22, 2020 4:09 pm
- Forum: Dipole Moments
- Topic: Polarity
- Replies: 30
- Views: 1719
Re: Polarity
If all of the dipole moments cancel out (by being of the same magnitude and in exact opposite directions), then the molecule will be nonpolar.
- Sun Nov 22, 2020 4:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polarity of BrF3
- Replies: 6
- Views: 1681
Re: Polarity of BrF3
If you look at the Lewis structure for this molecule, you can see that there are 5 regions of e- density, and 3 of them are occupied by atoms. The regions of e- density are arranged in a trigonal bipyramidal shape, and the two lone pairs occupy 2 of regions in the equatorial plane. So, if you were t...
- Sun Nov 22, 2020 3:48 pm
- Forum: Dipole Moments
- Topic: Trans-dichloroethene
- Replies: 5
- Views: 214
Re: Trans-dichloroethene
It is nonpolar because the two dipoles are going in exact opposite directions. When you add two vectors of equal magnitude and that are opposite direction, they cancel each other out. In the case of cis-dichloroethene, you can see that both vectors are facing right (one to the top-right and one to t...
- Sun Nov 22, 2020 2:46 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Number of Molecular Shapes
- Replies: 6
- Views: 281
Re: Number of Molecular Shapes
I believe there's a table in the book or you can look up a VSEPR chart online and you should find everything you need!
- Sun Nov 15, 2020 8:49 pm
- Forum: Resonance Structures
- Topic: Sapling #9 part b
- Replies: 2
- Views: 141
Re: Sapling #9 part b
Since the observed bond length is very close to the expected length of a Cl=O bond, you know that the bond has greater Cl=O bond character than Cl--O bond character. So I just chose the models that had more Cl=O bonds than Cl--O bonds.
- Sun Nov 15, 2020 8:45 pm
- Forum: Resonance Structures
- Topic: resonance structures
- Replies: 10
- Views: 549
Re: resonance structures
The ones that contribute the most are the ones that have formal charges closer to zero for all of the atoms in the molecule because neutral atoms require the least energy and therefore are more stable.
- Sun Nov 15, 2020 7:56 pm
- Forum: Bond Lengths & Energies
- Topic: Sapling #4
- Replies: 4
- Views: 396
Re: Sapling #4
Essentially that question was just asking how close the observed bond lengths matched up with the expected lengths for a single or double bond. You could say it has ample bond character for all of the expected bonds because the observed lengths were between both and not very noticeably closer to one...
- Sun Nov 15, 2020 5:02 pm
- Forum: Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)
- Topic: Dipole-dipole vs Dipole-induced dipole
- Replies: 5
- Views: 290
Re: Dipole-dipole vs Dipole-induced dipole
Dipole-dipole interactions occur between two polar molecules (which have permanent dipoles). Dipole-induced dipole interactions occur between a polar molecule and a nonpolar molecule, where, say, if the positively charged end of the polar molecule comes close to one end of the nonpolar molecule, tha...
- Sun Nov 08, 2020 10:23 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Formal charges and stability
- Replies: 5
- Views: 380
Re: Formal charges and stability
I think that since same charge particles repel each other, it would be lower energy if the charges were separated but I'm not completely sure.
- Sun Nov 08, 2020 10:09 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Pz Py Pz
- Replies: 5
- Views: 355
Re: Pz Py Pz
They are the three orbitals in the p (n=1) subshell.
- Sun Nov 08, 2020 5:40 pm
- Forum: Octet Exceptions
- Topic: 2C #15
- Replies: 6
- Views: 280
Re: 2C #15
The structure with the lowest energy would have formal charges closer to zero. However, I think it is also important to consider what charges are next to each other because two negatively charged atoms repel each other = more energy.
- Sun Nov 08, 2020 6:58 am
- Forum: Resonance Structures
- Topic: Valence Electrons [ENDORSED]
- Replies: 46
- Views: 4586
Re: Valence Electrons [ENDORSED]
The number of valence electrons corresponds to that element's column in the periodic table, ignoring the entire d-block. So, any element in the 1st column has 1 valence electron; any element in the "5th" column (the column with N at the top) has 5 valence electrons, etc.
- Sun Nov 08, 2020 6:46 am
- Forum: Ionic & Covalent Bonds
- Topic: Octet rule exceptions
- Replies: 15
- Views: 694
Re: Octet rule exceptions
For H and He, it's because those only have electrons in the 1s orbital (H has 1, He has 2), so they cannot have a full octet. Not really sure about the other 2 to be honest, but thanks for reminding me to look into that!
- Sun Nov 08, 2020 6:41 am
- Forum: Ionic & Covalent Bonds
- Topic: atomic radius
- Replies: 7
- Views: 379
Re: atomic radius
I believe neighboring atoms just means 2 of the same atoms that are directly next to each other with no space in between.
- Sun Nov 01, 2020 5:44 pm
- Forum: Trends in The Periodic Table
- Topic: Electron Shielding Question
- Replies: 3
- Views: 227
Re: Electron Shielding Question
Essentially the physical pull on the electron by the positively charged nucleus is weaker on electrons in the outer layers. This means that the outermost electrons are more easily removed from an atom. For example, Ca has 2 electrons in the n=2 subshell, so those are shielded by the inner electrons ...
- Sun Nov 01, 2020 5:38 pm
- Forum: DeBroglie Equation
- Topic: Sapling HW question 15
- Replies: 3
- Views: 203
Re: Sapling HW question 15
You can use the de Broglie equation to get the velocity of an electron in the beam and then use the formula KE = (1/2)mv^2 and convert to eV.
- Sun Nov 01, 2020 5:02 am
- Forum: Trends in The Periodic Table
- Topic: Question about Ionization energy
- Replies: 4
- Views: 220
Re: Question about Ionization energy
Ionization energy is just the amount of energy to remove an electron from an atom in the gas phase. First ionization energy refers specifically to the amount of energy to remove the first electron to create a cation with a +1 charge, and second ionization energy is the amount needed to remove a seco...
- Sat Oct 31, 2020 3:11 am
- Forum: Student Social/Study Group
- Topic: How to relax
- Replies: 168
- Views: 47269
Re: How to relax
I like to watch Netflix and listen to playlists and sometimes just stare at my ceiling for a little bit when I've been thinking for too long.
- Sun Oct 25, 2020 2:46 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Confusion with Uncertainty Values
- Replies: 7
- Views: 273
Re: Confusion with Uncertainty Values
Just wondering, but how come the uncertainty value is just 2x4 from 14.3 +/-4? If I were to write it out the long way, would it be since that the range is between 14.3-4 = 10 and 14.3 +4 = 18.3, and that the difference between the two is 8? I just need some clarification! I’m not sure where you got...
- Sun Oct 25, 2020 2:40 am
- Forum: Properties of Light
- Topic: Sapling problem
- Replies: 6
- Views: 665
Re: Sapling problem
For this problem, just know that the electron can move from n=6 to any lower energy level, meaning n=5, 4,3,2,1, which then gives 5 spectral lines. Then you find the energy of the n=6 to n=5 transition and get the wavelength for that photon, and do the same for the n=6 to n=1transition. Subtract the...
- Sun Oct 25, 2020 2:26 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Confusion with Uncertainty Values
- Replies: 7
- Views: 273
Re: Confusion with Uncertainty Values
Uncertainty is mainly about the range of values that the real value could be in. The actual value of the velocity doesn't really matter. For the question you specified, the uncertainty in velocity would be 4 m/s. Thank you for the clarification! I have a better understanding of it now. Do you know ...
- Fri Oct 23, 2020 1:04 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Sapling W 2,3,4 #12
- Replies: 4
- Views: 214
Re: Sapling W 2,3,4 #12
The steps you listed sound correct to me. Did you convert the wavelength from m to nm? That's all I can think of unless you maybe mixed up some variables.
- Fri Oct 23, 2020 12:58 am
- Forum: Molarity, Solutions, Dilutions
- Topic: Finding Formula of Unknown Molecule (Workshop)
- Replies: 4
- Views: 146
Re: Finding Formula of Unknown Molecule (Workshop)
I believe you made an error when you converted g of H2O to g of H because there are two H atoms in and H2O molecule. The mass of H should be double.
- Fri Oct 23, 2020 12:31 am
- Forum: Empirical & Molecular Formulas
- Topic: Amphetamine Formulas (Workshop Question)
- Replies: 2
- Views: 323
Re: Amphetamine Formulas (Workshop Question)
Yes it is since the mass of the empirical formula adds up to 135.21.
- Fri Oct 23, 2020 12:30 am
- Forum: Molarity, Solutions, Dilutions
- Topic: Arsenic Molarity Question
- Replies: 1
- Views: 173
Re: Arsenic Molarity Question
yes you did :)
- Sun Oct 18, 2020 2:51 am
- Forum: Photoelectric Effect
- Topic: Light Intensity
- Replies: 23
- Views: 666
Re: Light Intensity
Yes, the intensity of light is related to the number of photons! More photons = brighter light
- Sat Oct 17, 2020 3:07 am
- Forum: Photoelectric Effect
- Topic: Sapling homework
- Replies: 2
- Views: 136
Re: Sapling homework
yes!
- Fri Oct 16, 2020 2:50 am
- Forum: Properties of Electrons
- Topic: Week 2 Sapling HW #4
- Replies: 2
- Views: 155
Re: Week 2 Sapling HW #4
You were correct in finding the energy of the photon, but I think you made an error when subtracting E-K. Since it is approx. (8*10^-19 - 3*10^-19) you should get an answer closer to 5*10^-19 as your work function. Maybe you plugged in the wrong value for excess energy?
- Sat Oct 10, 2020 12:47 am
- Forum: Molarity, Solutions, Dilutions
- Topic: Question G.25 in Fundamentals
- Replies: 2
- Views: 147
Re: Question G.25 in Fundamentals
You are correct that moles of solute don't change when diluting a solution. The original 10 mL of solution contains .0010 mol of solute, and that number of moles stays the same throughout all 90 doublings of the volume. To find the final volume, you calculate 10*(2^90) , since one doubling is 10*2, ...
- Sat Oct 10, 2020 12:36 am
- Forum: Balancing Chemical Reactions
- Topic: Order of Balancing Rxns
- Replies: 23
- Views: 758
Re: Order of Balancing Rxns
I make a chart of every element for both reactants and products to keep track of how many of each element I have. I don't think I necessarily follow an order; I just go with what seems the most obvious at first, I think.
- Sat Oct 10, 2020 12:31 am
- Forum: Limiting Reactant Calculations
- Topic: Last Question on the Sapling Hw (Week 1)?
- Replies: 12
- Views: 607
Re: Last Question on the Sapling Hw (Week 1)?
You can multiply the volume of solution used in the reaction by the concentration of the solution (given in g/mL) to find out how many grams of 2-butanone was reacted, and then convert that mass to moles using the molar mass of 2-butanone. I assumed the equation was balanced, but you could check to ...