Search found 103 matches
- Mon Mar 15, 2021 2:11 pm
- Forum: Administrative Questions and Class Announcements
- Topic: CHEM COMMUNITY SCORES
- Replies: 16
- Views: 1218
Re: CHEM COMMUNITY SCORES
Yes the scores are additive. Your chemistry community grade should update each week based on the number of times you have posted so far.
- Sat Mar 13, 2021 9:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K
- Replies: 33
- Views: 1257
Re: K
K and Kc are calculated the same way and are sometimes used interchangeably. However, Kc specifically refers to molar concentrations.
- Sat Mar 13, 2021 9:35 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Final Bonus Q's
- Replies: 7
- Views: 409
Final Bonus Q's
I know that Prof Lavelle mentioned that there would be bonus questions for the final, does anyone know how much those bonus questions are worth?
- Sat Mar 13, 2021 9:32 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Order of Cell Diagrams
- Replies: 2
- Views: 230
Order of Cell Diagrams
I know how to determine which molecules go on the anode and cathode side of a cell diagram, however, I'm struggling with the order in which to write them. For example, Hg(l)|Hg2Cl2(s)|Cl−(aq)||Hg2^2+(aq)|Hg(l), how do you decide which molecule is closest to the salt bride?
- Wed Mar 10, 2021 9:27 pm
- Forum: Balancing Redox Reactions
- Topic: 6K.5 Part A
- Replies: 2
- Views: 144
6K.5 Part A
After balancing the oxygens in the half reaction for O3 --> O2, why do you add OH- to the product side and not the reactant side?
- Mon Mar 08, 2021 12:41 pm
- Forum: Administrative Questions and Class Announcements
- Topic: The Final
- Replies: 17
- Views: 797
The Final
For Chem14A, topics that we spent more time on had more questions pertaining to that content on the final. Does anyone know if Lavelle is doing the same thing for this final?
- Thu Mar 04, 2021 12:58 pm
- Forum: Student Social/Study Group
- Topic: Final
- Replies: 63
- Views: 3053
Re: Final
I find that the textbook problems are the most important thing you can do. I would also recommended reviewing sapling homework and utilizing office hours/UA sessions.
- Thu Mar 04, 2021 12:57 pm
- Forum: Student Social/Study Group
- Topic: Textbook Problem Strategies
- Replies: 17
- Views: 726
Re: Textbook Problem Strategies
I try to do every problem, however, there are instances when there's a lot of different problems that cover the same content. In that case, I start skipping questions that I've already had a lot of practice with.
- Wed Mar 03, 2021 8:15 pm
- Forum: First Order Reactions
- Topic: Slope
- Replies: 24
- Views: 838
Slope
Is the slope only equal to negative k(-k) in First Order Reactions or other reactions as well?
- Tue Mar 02, 2021 7:33 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.3 Part e [ENDORSED]
- Replies: 1
- Views: 89
6L.3 Part e [ENDORSED]
How do you know to reverse the reaction for tin and not for Mercury(I) chloride?
- Tue Mar 02, 2021 7:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Book Problems 6K.3 and 6L.5
- Replies: 1
- Views: 140
Book Problems 6K.3 and 6L.5
Does anyone know why we aren't provided with the cell potential values in these problems/aren't directed to a table? Is there a way to find them?
- Sat Feb 27, 2021 11:03 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Electron Flow in Electrolytic Cells
- Replies: 1
- Views: 137
Electron Flow in Electrolytic Cells
Since the anode is positively charged in electrolytic cells, does that affect the direction the electrons flow? Will they flow in the opposite direction now (cathode to anode)?
- Sat Feb 27, 2021 10:58 am
- Forum: General Rate Laws
- Topic: Rxn Rate Law for Lecture 21
- Replies: 3
- Views: 222
Rxn Rate Law for Lecture 21
In lecture 21, Lavelle mentioned how the preferred form for the 2NO2 + 2NO --> O2 reaction would be to divide the reaction rates for NO2 and NO by 2. Why is it better to divide NO2 and NO by 2, instead of just multiplying the reaction rate of O2 by 2?
- Fri Feb 26, 2021 11:09 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Anode/Cathode
- Replies: 45
- Views: 1429
Re: Anode/Cathode
Yes, the anode is always on the left and the cathode is always on the right. It also helps to keep the direction the electrons are flowing consistent.
- Fri Feb 26, 2021 10:34 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Labeling/Drawing Cell Diagrams
- Replies: 4
- Views: 273
Labeling/Drawing Cell Diagrams
Will we be asked to draw/label cell diagrams (ex. voltaic, concentration, or porous disk cells) in future exams?
- Thu Feb 25, 2021 12:37 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Reversing Half Rxn
- Replies: 3
- Views: 258
Reversing Half Rxn
When calculating standard cell potentials, how do you know which redox reaction to reverse/which E to make negative?
- Sat Feb 20, 2021 10:26 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Sign of work
- Replies: 17
- Views: 748
Re: Sign of work
I think about work in terms of the system. If work is being done ON the system, work is positive. However, if work is being done BY the system, it's negative.
- Thu Feb 18, 2021 7:58 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Standard Conditions
- Replies: 2
- Views: 178
Standard Conditions
What is the biggest difference between G,S, and H in standard conditions versus when they aren't in standard conditions? Does this affect calculations?
- Wed Feb 17, 2021 9:12 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: R Constant
- Replies: 91
- Views: 5224
Re: R Constant
I usually look at the units of pressure given and use the R value containing that unit.
- Wed Feb 17, 2021 9:09 am
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling Week 5/6 Question 12
- Replies: 2
- Views: 138
Sapling Week 5/6 Question 12
I'm having trouble grasping how to solve question 12. I know that the reaction is spontaneous when the Gibbs free energy is negative, however, I still can't get the correct answers.
- Mon Feb 15, 2021 10:44 am
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm 2
- Replies: 14
- Views: 558
Midterm 2
Does anyone know if midterm 2 will have partial credit and to what extent?
- Sun Feb 14, 2021 7:08 pm
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Midterm #2
- Replies: 3
- Views: 194
Re: Midterm #2
Yeah the midterm is Friday, Feb 19th at the time of your lecture.
- Sun Feb 14, 2021 6:59 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Can We Review our Exams?
- Replies: 69
- Views: 2937
Re: Can We Review our Exams?
To review your exams, you can go to your TA office hours and possibly in discussion(in a breakout room) if you have extra time.
- Sun Feb 14, 2021 6:58 pm
- Forum: Administrative Questions and Class Announcements
- Topic: struggling
- Replies: 73
- Views: 3501
Re: struggling
I think the step-up sessions will be most useful to you because the chemistry content is explained at a slower pace. Utilizing office hours and forming study groups with peers can also be very beneficial.
- Sun Feb 14, 2021 6:54 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Using CV versus nCV
- Replies: 3
- Views: 160
Using CV versus nCV
In Sapling week 5/6 question 5, I noticed that we multiplied the cv value by moles to convert to nCV. However, in question 6, the CV value was used for the change in temperature. In what cases, do you use CV and in what cases do you use nCV?
- Wed Feb 10, 2021 8:27 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: R Constant
- Replies: 91
- Views: 5224
Re: R Constant
The R constant you choose to do your calculations with is based on the units of pressure you're given. If you're given pressure in atm, then use the gas constant that has atm in the units.
- Thu Feb 04, 2021 8:54 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: endothermic/exothermic Q and K
- Replies: 16
- Views: 2006
Re: endothermic/exothermic Q and K
A negative delta H means that the reaction is exothermic and that heat is being released. A positive delta H means that the reaction is endothermic and that heat is required. Q isn't affected by a temperature change because there's no change in concentration. However, increasing temperature for an e...
- Thu Feb 04, 2021 8:49 am
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Thermodynamics Equilibria
- Replies: 1
- Views: 105
Thermodynamics Equilibria
I know that a a system is at equilibrium when internal and external pressure are equal. However, does the system being closed, open, or isolated affect the system's equilibrium as well?
- Wed Feb 03, 2021 7:37 am
- Forum: Administrative Questions and Class Announcements
- Topic: HW Due Date
- Replies: 15
- Views: 624
Re: HW Due Date
Professor Lavelle moved the due date for homework weeks 3/4 to Sunday, February 6.
- Tue Feb 02, 2021 7:56 am
- Forum: Administrative Questions and Class Announcements
- Topic: Partial Credit on MT 1
- Replies: 15
- Views: 723
Re: Partial Credit on MT 1
On the 10 point questions, there's partial credit for answers that were close to the correct answers. However, questions lower than 10 points don't have partial credit.
- Mon Feb 01, 2021 9:10 am
- Forum: General Science Questions
- Topic: Studying
- Replies: 67
- Views: 3521
Re: Studying
I find that textbook problems are the most important resource when studying for 14B exams. Additionally, office hours are quite helpful. I usually study over a week so I can give myself time to thoroughly understand the maerial.
- Sat Jan 30, 2021 12:09 pm
- Forum: Phase Changes & Related Calculations
- Topic: when to assume x is insignificant
- Replies: 86
- Views: 6400
Re: when to assume x is insignificant
When the equilibrium constant is 10^-4 or smaller, it's safe to just approximate. However, you can run into errors when you're calculating percent ionization. If your percent is greater than 5%, then you're going to have to re-do the calculation without the approximation.
- Wed Jan 27, 2021 8:58 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K Values that aren't specified
- Replies: 2
- Views: 122
K Values that aren't specified
If we're just given the value of K without specifying Kc or Kp, what units should we use for our calculations? Pressure or molarity?
- Wed Jan 27, 2021 11:56 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Using the ICE table
- Replies: 36
- Views: 1314
Re: Using the ICE table
Yes, the ice tables are applicable for partial pressure, as well as concentration. They can even be used to calculate just moles.
- Wed Jan 27, 2021 11:55 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Sapling Week 3/4 Question 5
- Replies: 2
- Views: 115
Sapling Week 3/4 Question 5
Does anyone know how to solve this? Initially I thought it was the sum of product enthalpy minus the sum of reactant enthalpy. However, I can't seem to calculate the correct answer.
- Tue Jan 26, 2021 9:04 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Total Pressure
- Replies: 26
- Views: 1838
Re: Total Pressure
If you're prompted to find total pressure, you need to calculate each equilibrium partial pressure and add them all together. This will give you total pressure and typically, you want your units to be in bars.
- Fri Jan 22, 2021 10:29 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Increasing pressure
- Replies: 23
- Views: 865
Re: Increasing pressure
Adding a gas to increase pressure won't affect the system, however, compressing the system to increase pressure will cause equilibrium to shift.
- Thu Jan 21, 2021 9:22 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: When would K be unchanged?
- Replies: 31
- Views: 1058
Re: When would K be unchanged?
The most important rule to remember is that K can only be changed by the temperature. When the concentration of products increases/decreases, the concentration of reactants will increase/decrease accordingly to maintain the same ratio of K.
- Thu Jan 21, 2021 9:13 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Including (aq) Solvents
- Replies: 4
- Views: 218
Including (aq) Solvents
I know that professor Lavelle has said not to include liquids/solvents in your calculation of the equilibrium constant. However, if your solvent is aqueous, can it be included?
- Wed Jan 20, 2021 12:01 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5.61 PART B
- Replies: 3
- Views: 121
5.61 PART B
The solution manual states that compressing the system has no effect because there's an equal number of moles on both sides. However, the equation has 12 moles on the reactant side and 7 on the product side. Can someone explain if I'm missing something?
- Tue Jan 19, 2021 11:12 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5.35 PART A
- Replies: 1
- Views: 118
5.35 PART A
I'm having trouble with part A. How do you figure out the coefficients for A,B, and C by looking at the graph?
- Fri Jan 15, 2021 2:18 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: 5J.11 Part b
- Replies: 2
- Views: 88
5J.11 Part b
In 5J.11 part b X2(g) ⇌ 2X(g), where X is a halogen. The solutions manual states that this reaction is endothermic and that heat is on the reactants side. How can you tell that this reaction is endothermic?
- Thu Jan 14, 2021 9:34 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: H2O as a Gas
- Replies: 69
- Views: 6150
Re: H2O as a Gas
H2O would still be included as a gas. When it's a liquid/solvent, then we wouldn't include it.
- Thu Jan 14, 2021 9:31 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE
- Replies: 7
- Views: 257
Re: ICE
I think it's especially important to pay attention to the words "equilibrium" and "initial". If only equilibrium concentrations are present, then I think it's safe to assume that the ICE tables aren't necessary. However, if initial concentrations are present, then using an ICE ta...
- Wed Jan 13, 2021 11:58 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5G.9 part c
- Replies: 3
- Views: 90
5G.9 part c
Why does PO2/PO3 differ between the two cases and how would you calculate it to verify your answer? I tried calculating the concentration of O2 and computed the equilibrium constant without raising the answer to their respective powers, however, I can't get an answer that verifies the above statement.
- Tue Jan 12, 2021 9:30 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook Problem 5H.3
- Replies: 3
- Views: 174
Textbook Problem 5H.3
Why do you multiply the equilibrium constants instead of adding them?
- Fri Jan 08, 2021 10:33 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: names for reaction quotient Q
- Replies: 19
- Views: 494
Re: names for reaction quotient Q
Qc is used for molar concentration, Qp is used for partial pressure, and Q represents the reaction quotient in general. However, Qc, Qp, and Q are all calculated the same as K. The products will be in the numerator and the reactants in the denominator.
- Thu Jan 07, 2021 10:59 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chemical Equilibrium Part 3 Module
- Replies: 2
- Views: 127
Chemical Equilibrium Part 3 Module
I understand the steps needed to solve these kinds of questions, however, we weren't given the equilibrium constant in the question description. How would you go about solving this particular question?
- Wed Jan 06, 2021 12:23 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Converting bar to mol/L
- Replies: 5
- Views: 3119
Converting bar to mol/L
I've been having trouble with converting bars to mol/L. Does bar have to be converted to another unit first or can it just be immediately plugged into the ideal gas law equation?
- Wed Jan 06, 2021 12:20 pm
- Forum: Student Social/Study Group
- Topic: Advice for someone who didn't take 14A with professor Lavelle
- Replies: 61
- Views: 2686
Re: Advice for someone who didn't take 14A with professor Lavelle
Professor Lavelle provides TONS of live resources to assist you in this course and is always willing to help. I would utilize officer hours, UA sessions, step-up sessions, and etc. for any areas of confusion. In my opinion, doing the textbook problems is the most important thing you can do to succeed.
- Tue Jan 05, 2021 11:50 am
- Forum: Ideal Gases
- Topic: Units of Temperature
- Replies: 82
- Views: 3356
Units of Temperature
When using the ideal gas law, which units should the temperature be in? Kelvins or Celsius?
- Fri Dec 11, 2020 11:36 am
- Forum: Administrative Questions and Class Announcements
- Topic: Final Content
- Replies: 18
- Views: 963
Re: Final Content
He states earlier that the final is cumulative and the subjects we spent more time on will have more questions in the final. For example, we spent the most time of the quantum section, so you can expect to have more questions about that topic.
- Thu Dec 10, 2020 4:26 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Textbook Problems on the Final
- Replies: 5
- Views: 364
Re: Textbook Problems on the Final
I think he meant that he will draw some questions from the book outline, but not all. However, redoing book problems can still be valuable and beneficial. I wouldn't rely on the idea that he will ONLY pull from homework problems, but expect some.
- Thu Dec 10, 2020 9:54 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Determining Shape
- Replies: 10
- Views: 668
Re: Determining Shape
Electron geometry focuses on all regions of electron density(including lone pairs). However, molecular shape just looks at the regions of electron density occupied by atoms. For example, NH3 has a tetrahedral electron geometry, but a trigonal pyramidal molecular shape because only 3/4 regions of e- ...
- Tue Dec 08, 2020 8:58 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: 9C.3 Part C & D
- Replies: 1
- Views: 81
9C.3 Part C & D
In what case do you use OH2 and in what case do you use H2O?
- Tue Dec 08, 2020 8:56 pm
- Forum: Naming
- Topic: [Co(NH3)5 Cl] Cl 2H2O
- Replies: 5
- Views: 281
[Co(NH3)5 Cl] Cl 2H2O
Why is H2O referred to as dihydrate instead of diaqaua in this coordination compound? Is it because H2O is not directly bonded to Co?
- Mon Dec 07, 2020 10:04 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Ligand Classification
- Replies: 2
- Views: 178
Ligand Classification
I've been struggling to grasp ligand classification. I understand the definition of monodentate, bidentate, tridentate, and hexadentate, however, I don't understand how to determine if an ion or molecule is one of those types. I need some strategies to help with determining what type of ligand the i...
- Fri Dec 04, 2020 9:39 am
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3009128
Re: Post All Chemistry Jokes Here
Q: Why does hamburger yield lower energy than steak?
A: Because it's in the ground state.
A: Because it's in the ground state.
- Thu Dec 03, 2020 10:53 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: polar v nonpolar molecules
- Replies: 30
- Views: 2317
Re: polar v nonpolar molecules
I know that Professor Lavelle said we wouldn't be drawing vectors, but I still use them to determine if something is polar or nonpolar. A polar molecule's vectors/dipoles DON'T cancel and a non polar molecule's dipoles/vectors DO cancel. I also look at the electronegativity values to help. Typically...
- Thu Dec 03, 2020 10:49 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 2E.25 Part D
- Replies: 2
- Views: 149
2E.25 Part D
I noticed that the textbook made a mistake and drew the Lewis structure for SCl4 instead of SF4. However, I was wondering if SF4 would still be polar because the molecule still has the same shape and since F is more electronegative than S.
- Wed Dec 02, 2020 10:41 am
- Forum: Lewis Structures
- Topic: 2E.25 Part A
- Replies: 2
- Views: 132
2E.25 Part A
For 2E.25 part A, how do you know to draw the Cl's on the same side and the H's on the same side. If you draw them opposite each other, then the vectors will cancel out. However, I'm unsure how to determine where you place the atoms.
- Wed Dec 02, 2020 10:35 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Question 2E.21 Part D
- Replies: 2
- Views: 156
Question 2E.21 Part D
For question 2E.21 Part D, how can we determine the bond angle without looking it up online. N2H4 has a trigonal pyramidal shape, and a bond angle of 107 degrees. I know how to determine if the angle is above/below 120/109.5, but I'm unsure how to find the exact angle for shapes that aren't tetrahed...
- Fri Nov 27, 2020 12:10 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond Angles
- Replies: 25
- Views: 924
Re: Bond Angles
I think we will have to memorize the bond angels for shapes that have a consistent bond angles such as tetrahedral, trigonal planar, and linear. For other shapes, we most likely just need to know if it's above or below 120 degrees or 109.5 degrees.
- Fri Nov 27, 2020 12:07 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: trigonal planar vs trigonal pyramidal
- Replies: 9
- Views: 684
Re: trigonal planar vs trigonal pyramidal
You want to look at how many regions of electron density are around the central atom. Regions of electron density can be lone pairs or bonding pairs, but it's also important to note that a single bond, double bond, and a triple bond are each one region of electron density. When drawing NH3, N had 3 ...
- Wed Nov 25, 2020 1:25 pm
- Forum: Bond Lengths & Energies
- Topic: Tetrahedral Bond Angle
- Replies: 7
- Views: 449
Re: Tetrahedral Bond Angle
When dealing with shapes like tetrahedral(109.5 degrees) and trigonal planar(120 degrees), those shapes have consistent bond angles, so I feel that it's best to memorize those. However, for shapes like trigonal pyramidal, seesaw, bent, etc., knowing if they're above/below 109.5 or above/below 120 is...
- Wed Nov 25, 2020 1:21 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: SeeSaw Molecular Shape
- Replies: 2
- Views: 141
SeeSaw Molecular Shape
When looking at the lecture notes and book problems, I saw that the Seesaw molecular shape can have multiple bond angles, however, I'm not sure why that is. I was wondering if someone could further explain that. Lastly, when does the Seesaw shape have the bond angles 90 and 120 and when does it have...
- Tue Nov 24, 2020 10:56 am
- Forum: Hybridization
- Topic: Hybridization techniques
- Replies: 4
- Views: 360
Hybridization techniques
I'm still having trouble grasping hybridization. I know that we can look at the number of regions of electron density that are present and determine hybridization from there. However, I want to learn how to do it past memorization. Does anyone have any techniques they have used to increase their und...
- Thu Nov 19, 2020 11:22 am
- Forum: Lewis Structures
- Topic: H2O Lone Pairs
- Replies: 5
- Views: 379
H2O Lone Pairs
Professor Lavelle recently mentioned that lone pairs are usually drawn farther or opposite from each other due to repulsion. However, I was wondering why the lone pairs are H2O are drawn next to each other. Why aren't they drawn opposite each other on opposite sides of the Oxygen?
- Wed Nov 18, 2020 1:57 pm
- Forum: Administrative Questions and Class Announcements
- Topic: The Final
- Replies: 1
- Views: 146
The Final
I know that our midterms have been during our discussion time, however, it may be difficult to test us on the whole/or most of the course's content in 50 mins. On MyUCLA for Lecture 2, it says our final is on December 13th from 11:30AM to 2:30PM. Will we have to take the exam at that exact time or w...
- Tue Nov 17, 2020 12:03 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: London Dispersion Forces
- Replies: 9
- Views: 1879
London Dispersion Forces
When two different compounds are both experiencing ONLY London Dispersion Forces, how can you determine which one is experiencing greater London Dispersion Forces? What criteria are we supposed to look at?
- Mon Nov 16, 2020 7:59 am
- Forum: Lewis Structures
- Topic: Lewis Structure w/ 4+ atoms
- Replies: 4
- Views: 365
Lewis Structure w/ 4+ atoms
When drawing Lewis structures that have more than 4 atoms that are different, how to you ensure that you are placing the atoms in the correct place. I always make sure I have the right amount of electrons, and that each atom is satisfied with the octet rule, but I still run into some trouble. For ex...
- Mon Nov 16, 2020 7:54 am
- Forum: Bond Lengths & Energies
- Topic: 2D.13 Part B
- Replies: 3
- Views: 182
2D.13 Part B
The final answer for this textbook problem was that SO3^2- had the longest S-O bond length and SO2 and SO3 had equal S-O bond lengths. In these problems, should we always try to draw oxygen with a double bond because it has a lower Formal Charge? Initially, I had drawn the SO2 and SO3 structure with...
- Thu Nov 12, 2020 5:46 pm
- Forum: Trends in The Periodic Table
- Topic: Which directions do cation and anions of elements move?
- Replies: 3
- Views: 183
Re: Which directions do cation and anions of elements move?
Br 2- would be two to the right of the periodic table. Anions like to form noble gas configuration to gain stability, so you will add e- and move to the right.
- Thu Nov 12, 2020 10:04 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: F-block?
- Replies: 7
- Views: 283
Re: F-block?
I don't think we need to worry about the f-block for the exam, however, I think it's good to have a basic understanding of it to enhance your performance on the exam. By general understand, I mean how many orbitals it has, where it begins on the periodic table, etc.
- Wed Nov 11, 2020 9:40 am
- Forum: Lewis Structures
- Topic: Double Bonds
- Replies: 11
- Views: 274
Double Bonds
When drawing a Lewis structure like COCl2, how do you decide if the CL or O gets the double bond? Is it usually the element with the higher ionization energy?
- Wed Nov 11, 2020 9:33 am
- Forum: Lewis Structures
- Topic: Octet Expansion
- Replies: 3
- Views: 162
Octet Expansion
When drawing Lewis structures, when are elements allowed to have more than 8 electrons? In other words, when is the octet expansion allowed? I know Professor Lavelle has touched on the reason in lecture, but I'm still a little confused.
- Mon Nov 09, 2020 12:34 pm
- Forum: Lewis Structures
- Topic: 2C.15 Part b
- Replies: 1
- Views: 59
2C.15 Part b
For question 2c.15 part b, I noticed that the book might have made a mistake when drawing the Lewis Structure. When drawing HSO4^-1, the structure on the right has an unsatisfied single bonded O. It only has 2 lone pairs, 1 bonding pair, and doesn't follow the octet rule. However, in the answer key,...
- Thu Nov 05, 2020 9:03 pm
- Forum: Student Social/Study Group
- Topic: Final Jitters
- Replies: 457
- Views: 334347
Re: Final Jitters
Another technique that I find best for myself is by being confident and giving myself positive affirmations. If I come into an exam convinced I'm going to perform badly, then I most likely will. Avoid worrying about worst-case scenarios and remain optimistic!
- Wed Nov 04, 2020 10:51 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: F orbitals?
- Replies: 21
- Views: 712
Re: F orbitals?
I don't think we will be tested on f orbitals or required to know about configurations with them. However, I think he would just like for us to know that they're there and some general information about the f orbitals.
- Tue Nov 03, 2020 8:22 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Noble Gas Configuration
- Replies: 13
- Views: 480
Re: Noble Gas Configuration
By looking at both options, they do make sense. However, just putting [Ar] may be a little vague or confusing. I think you should stick with starting from [Ne] and writing the remaining configurations.
- Mon Nov 02, 2020 10:36 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Electron Configuration For Calcium
- Replies: 7
- Views: 267
Re: Electron Configuration For Calcium
In order for 3d to come before 4s, the 4s orbitals must be completely filled(4s2). At this point, 3d is lower in energy than 4s. However, this doesn't apply to exceptions like Copper and Chromium.
- Mon Nov 02, 2020 10:29 am
- Forum: Quantum Numbers and The H-Atom
- Topic: Quantum # ml
- Replies: 3
- Views: 106
Quantum # ml
I know that quantum number ml corresponds to a specific orbital. However, I was wondering how you know that when n =2 l= 1ml= -1, it's 2px. Specifically, how does the coefficient and charge of ml help you determine whether it's x, y or z or even x^2...?
- Fri Oct 30, 2020 1:51 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Shorthand Electron Configurations
- Replies: 6
- Views: 1596
Re: Shorthand Electron Configurations
When using shorthand notation, the [KR] symbolizes the electron configuration of Krypton gas. So all that's left to do is use the building-up principle and write the remaining electron configuration until Iodine. In this case, the remaining configurations that lead to Iodine are 4d10 5s2 5p5. The d ...
- Thu Oct 29, 2020 10:42 am
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Textbook Problem 1E.13 part a
- Replies: 3
- Views: 104
Textbook Problem 1E.13 part a
For this textbook problem for part a, we had to write the electron configuration for Ag. The textbook listed it as [Kr] 4d10 5s1. I remember Chromium and Copper were listed as exceptions, but I don't remember Silver. Is this an instance where Silver is an exception or did the book make a mistake?
- Wed Oct 28, 2020 11:36 am
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm 2 and Final
- Replies: 9
- Views: 398
Midterm 2 and Final
I know this is far in the future, but does anyone know if Midterm 2 and the final are cumulative or if they just cover the content we learn in between each exam?
- Wed Oct 28, 2020 11:32 am
- Forum: Properties of Electrons
- Topic: Electron Spin
- Replies: 7
- Views: 262
Electron Spin
I know that two electrons can only exist in an orbital if they have an opposite spin. However, I'm still confused about how to determine which electron has a +1/2 or -1/2 spin. Does the first electron in the orbital typically have a +1/2 spin and the second a -1/2 spin?
- Mon Oct 26, 2020 6:41 pm
- Forum: Limiting Reactant Calculations
- Topic: What counts as theoretical yield?
- Replies: 8
- Views: 415
Re: What counts as theoretical yield?
Theoretical yield also differs from actual yield because it's the maximum amount of product one can get from a molecule/atom/formula unit in grams based on the limiting reactant. It is always greater than actual yield due to side reactions, reactants not being pure, and product sticking to the beake...
- Thu Oct 22, 2020 8:53 am
- Forum: Properties of Light
- Topic: Frequency and Wavelength on Light Spectrum
- Replies: 5
- Views: 241
Re: Frequency and Wavelength on Light Spectrum
By knowing which wavelengths each EM region corresponds to, you can also just calculate the frequency using c= wavelength x frequency. This way you won't have to memorize the frequency ranges. Hope this helps! :)
- Wed Oct 21, 2020 10:31 am
- Forum: Administrative Questions and Class Announcements
- Topic: The Midterm Topics
- Replies: 5
- Views: 212
The Midterm Topics
They're some things such as net equations and organic chemistry formulas that have come up in book problems and previous homework. Will we be expected to use/know these subtopics on the midterm even if we haven't covered them in class?
- Tue Oct 20, 2020 10:00 am
- Forum: Administrative Questions and Class Announcements
- Topic: The Midterm
- Replies: 9
- Views: 275
The Midterm
Does anyone know if we will have an equation sheet with constants given to us during the midterm or if we have to memorize that information?
- Mon Oct 19, 2020 9:30 pm
- Forum: Balancing Chemical Reactions
- Topic: Formula Unit vs. Molecules
- Replies: 3
- Views: 1095
Formula Unit vs. Molecules
When reading the Balancing Chemical Equations section in the textbook, they refer to NaOH as a formula unit, but H2O as a molecule. What is the difference between those two terms and how do you know how to categorize the compounds in regards to these terms( which are formula units and which are mole...
- Mon Oct 19, 2020 11:24 am
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Question 18 from Heisenberg Uncertainty Module
- Replies: 3
- Views: 79
Question 18 from Heisenberg Uncertainty Module
Does anyone know how to solve this? I've tried multiple methods, but I can't seem to figure it out.
- Thu Oct 15, 2020 11:36 am
- Forum: Balancing Chemical Reactions
- Topic: States of Molecules
- Replies: 9
- Views: 379
Re: States of Molecules
I find that writing the state of the molecules helps me visualize and understand how it takes place. Thought at times, it may not be necessary, writing the states may increase your overall understanding of the chemical reaction. I would also get in the habit of listing states so that you aren't mark...
- Wed Oct 14, 2020 11:38 am
- Forum: Properties of Light
- Topic: Textbook Problem 1A. 3
- Replies: 7
- Views: 319
Textbook Problem 1A. 3
In question 3 of focus topic IA, I understand why options A,B, and D are wrong. However, I do not understand why C is correct. I am confused about how the extent of change in the electrical field relates to EM radiation. What is the "extent of change" referring to in the question? The word...
- Tue Oct 13, 2020 9:48 am
- Forum: General Science Questions
- Topic: Balancing equations
- Replies: 19
- Views: 2494
Re: Balancing equations
Hello everyone! I hope you all are doing fine. My question is when you balance any equation is there only one correct way of doing it or can there be different approaches and answers? I also find it easier to begin balancing the atom that only shows up in one compound on both sides. For example, wh...
- Tue Oct 13, 2020 9:40 am
- Forum: Limiting Reactant Calculations
- Topic: M11 Part C
- Replies: 2
- Views: 82
M11 Part C
I am unsure how to begin solving part C of M11. How do you use the formation of P4O6 to solve the problem?
- Mon Oct 12, 2020 11:39 am
- Forum: Photoelectric Effect
- Topic: Electron Emission
- Replies: 5
- Views: 177
Re: Electron Emission
Chem_Mod wrote:Is there a particular problem you are referring to?
I am referring to question 18 in the Photoelectric effect module. It asks what conditions must occur for an election to be emitted from a metal surface.
- Mon Oct 12, 2020 11:35 am
- Forum: Empirical & Molecular Formulas
- Topic: M19
- Replies: 2
- Views: 109
M19
To determine the empirical formula of the substance, we must convert the moles of the compounds to moles of elements within the compounds (ex. finding moles of Hydrogen within moles of H2O). However, when solving the problem, the book multiples the moles of H2O by 1 instead of 2. I am confused about...
- Thu Oct 08, 2020 11:06 am
- Forum: Photoelectric Effect
- Topic: Electron Emission
- Replies: 5
- Views: 177
Electron Emission
If the energy of the light photon is equal to the energy required to remove the electron, why is the electron still ejected from the surface if its kinetic energy is zero?
- Wed Oct 07, 2020 1:30 pm
- Forum: Limiting Reactant Calculations
- Topic: Sapling Homework Question 10
- Replies: 16
- Views: 672
Re: Sapling Homework Question 10
I know that "points" on the diagrams translate to carbon molecules. However, on 3-methyl-3-hexanol, they're two vertical lines pointing upwards. What does that translate to when finding the molecular formula?