Search found 103 matches
- Fri Mar 12, 2021 5:09 pm
- Forum: General Rate Laws
- Topic: Intermediate OH- present in overall rate law [ENDORSED]
- Replies: 2
- Views: 246
Intermediate OH- present in overall rate law [ENDORSED]
Hello! In question 7.23 of the textbook, the overall equation is ClO- + I- --> Cl- + IO-. The solution manual goes through the step of removing an intermediate from the rate law found in the slow step, however OH- is present in the overall rate law that is found using this method with the final rate...
- Wed Mar 10, 2021 8:52 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6L.7
- Replies: 3
- Views: 217
6L.7
6L.7 Write the half-reactions and devise a galvanic cell (write a cell diagram) to study each of the following reactions: (a) AgBr(s) <--> Ag+(aq) + Br-(aq), a solubility equilibrium (b) H+(aq)+OH-(aq)<--> H2O(l), the Brønsted neutralization reaction (c) Cd(s) + 2 Ni(OH)3(s) S <--> Cd(OH)2(s) + 2 Ni...
- Wed Mar 10, 2021 3:01 pm
- Forum: First Order Reactions
- Topic: Graphing
- Replies: 20
- Views: 943
Re: Graphing
While I am not sure of this, I think it would be safe to assume that we would not need to graph anything (as none of the textbook questions assigned require us to do this) and that questions relating to graphs would have to do with determining the rate of the reaction based on the axis of the graph ...
- Wed Mar 10, 2021 2:59 pm
- Forum: Reaction Mechanisms, Reaction Profiles
- Topic: what is slow? fast?
- Replies: 11
- Views: 1463
Re: what is slow? fast?
The slow step is the rate determining step, or the step from which the rate can be determined. The other steps can be considered fast. It is sometimes asked that you identify which step is the slow step, and in order to do this you would have to compare the experimentally determined rate law for the...
- Wed Mar 10, 2021 2:50 pm
- Forum: Environment, Ozone, CFCs
- Topic: catalysis vs intermediate
- Replies: 25
- Views: 1930
Re: catalysis vs intermediate
And intermediate is something that is produced in one step of the reaction, and used in a subsequent step. It does not appear in the overall reaction as it is created and used in the process of the overall reaction. A Catalyst is something that is necessary for the reaction to occur. It shows up on ...
- Thu Mar 04, 2021 8:56 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6M.11 phases of galvonic cell components
- Replies: 2
- Views: 132
Re: 6M.11 phases of galvonic cell components
Hi, I might be wrong but I believe that all ions will be aqueous in all of these reactions, for any element. Also all non-charged metal species, like Cobalt we can assume are solid. The only metal that isn't solid at standard conditions is mercury, so I'd expect that it wouldn't be found in a galva...
- Thu Mar 04, 2021 6:35 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: 6M.11 phases of galvonic cell components
- Replies: 2
- Views: 132
6M.11 phases of galvonic cell components
For the galvanic cell Co 2+ /Co and Ti 3+ /Ti 2+ , I understand how to figure out which is the cathode and anode, but how you determine what is solid, liquid, or aqueous when drawing the shorthand for the galvanic cell? Ti 3+ and Ti 2+ are both supposed to be aqueous, Co 2+ is aqueous, and Co is sol...
- Thu Mar 04, 2021 11:46 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams Shorthand
- Replies: 2
- Views: 168
Re: Cell Diagrams Shorthand
My TA had this helpful overview • Salt bridge: Two vertical lines (||) • Different phase: One vertical line (I) • Same phase: One coma (,) Diagram order: Inert Metal – Anode – salt bridge - Cathode – Inert Metal Thank you so much this is super helpful! Any advice on determining what goes on the far...
- Thu Mar 04, 2021 12:16 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams Shorthand
- Replies: 2
- Views: 168
Cell Diagrams Shorthand
Could someone explain how to write cell diagram shorthand from an equation? Are there any rules for how things are ordered? is the left always oxidation and right always reduction? There aren't any clear rules set out in the textbook and I am getting a bit confused as every example seems to be order...
- Sat Feb 27, 2021 8:00 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation vs Reduction
- Replies: 30
- Views: 1256
Re: Oxidation vs Reduction
the half reaction where an electron is seen on the left (with the reactants) is reduction
- I remember if the electron is written with the *R*eactants, it is *R*eduction
The half reaction where an electron is seen on the right (as a product) is oxidation
- I remember if the electron is written with the *R*eactants, it is *R*eduction
The half reaction where an electron is seen on the right (as a product) is oxidation
- Sat Feb 27, 2021 7:53 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: n in NFE
- Replies: 64
- Views: 2931
Re: n in NFE
To find n, write the two half reactions with equal charges. The number of electrons transferred in the overall balanced reaction is the value of n.
- Sat Feb 27, 2021 7:48 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Nernst K vs Q
- Replies: 14
- Views: 896
Re: Nernst K vs Q
K is the equilibrium constant, whereas Q is the ratio of products to reactants at any point in the reaction.
- Sat Feb 27, 2021 7:43 pm
- Forum: Balancing Redox Reactions
- Topic: Balancing Acidic Versus Basic Solutions
- Replies: 20
- Views: 859
Re: Balancing Acidic Versus Basic Solutions
When I learned how to balance Redox reactions, I learned to start by balancing both reactions in the same way: (1) balance non H or O elements (2) add H2O to balance O (3) add H+ to the opposite side to balance H (4) Balancing overall charge For an acidic reaction, you can leave it in this state, an...
- Sat Feb 27, 2021 7:38 pm
- Forum: Student Social/Study Group
- Topic: Final
- Replies: 63
- Views: 3045
Re: Final
For me, the most useful thing is doing all of the assigned textbook problems. I usually go through once to make sure I know how to do all of the problems, then go through again and instead of solving the problems I just think through the steps that it would take to solve the problem and comparing my...
- Sat Feb 27, 2021 12:27 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Sapling #17 Week 7-8
- Replies: 2
- Views: 235
Re: Sapling #17 Week 7-8
The reaction in a standard hydrogen electrode (S.H.E.) is 2H+(aq) + 2e- <---> H2(g). Because a S.H.E. is at standard conditions, the standard cell potential, E naught, is 0. You can plug zero into the Nernst equation for the E naught slot :) As for Q, my TA explained that you can use (4.3 atm)/((0....
- Fri Feb 26, 2021 11:08 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Sapling #17 Week 7-8
- Replies: 2
- Views: 235
Sapling #17 Week 7-8
Question 17 states: What would the potential of a standard hydrogen electrode (S.H.E.) be under the given conditions? [H+]=0.82 PH2=4.3 atm. T=298 K the answer is calculated with a Q value that uses the concentration of the products in partial pressure but the concentration of reactants in molar con...
- Sun Feb 21, 2021 5:18 pm
- Forum: Calculating Work of Expansion
- Topic: Work Formula
- Replies: 15
- Views: 745
Re: Work Formula
This formula is looking at the work of expansion done by a system do to an increase in moles of gas. You can ignore the amounts of liquid and solids as they do not contribute much to this expansion work.
- Sun Feb 21, 2021 5:10 pm
- Forum: Van't Hoff Equation
- Topic: Celcius vs Kelvin for T1 and T2
- Replies: 84
- Views: 6440
Re: Celcius vs Kelvin for T1 and T2
unless the value for temperature is a change in temperature (ie ∆T as in the equation q=mC∆T), then it matters whether you use K or Celcius. For most equations that use a value of R, temperature must be in Kelvin, so a safe bet would be to convert to Kelvin however it is always important to look at ...
- Sun Feb 21, 2021 5:05 pm
- Forum: Student Social/Study Group
- Topic: Winter GEs?
- Replies: 33
- Views: 2478
Re: Winter GEs?
Musicology 68 is an amazing GE for Foundation of Arts and Humanities -Visual and Performance Arts Analysis and Practice. I believe that is offered winter each year. Its all about the history of the Beatles, and most classes you get to sit and listen to an entire album or watch a movie, and the lectu...
- Sun Feb 21, 2021 5:01 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: R gas constant and kPa or Pa
- Replies: 9
- Views: 3030
Re: R gas constant and kPa or Pa
I would suggest converting kPa into atmospheres or another quantity for pressure that is listed as part of an R value. To determine what form to convert the pressure to, look at the units of the other quantities given (ie moles, liters, etc)
- Sun Feb 21, 2021 4:59 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Stable vs Unstable Gibbs Free Energy
- Replies: 16
- Views: 2348
Re: Stable vs Unstable Gibbs Free Energy
I believe that if a molecule is stable, its standard gibbs free energy of formation will be negative, indicating that the molecule in its standard state is more stable than its elements in their most standard state. Conversely, if a molecule is unstable, its standard gibbs free energy of formation w...
- Wed Feb 17, 2021 10:17 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: question 4.7 combustion forming liquid water
- Replies: 1
- Views: 163
question 4.7 combustion forming liquid water
for the question: (a) Calculate the work that must be done against the atmosphere for the expansion of the gaseous products in the combustion of 1.00 mol C6H6(l) at 25 8C and 1.00 bar. (b) Using data in Appendix 2A, calculate the standard enthalpy of the reaction. (c) Calculate the change in interna...
- Fri Feb 12, 2021 4:53 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Focus 4 question 1
- Replies: 1
- Views: 108
Focus 4 question 1
Air in a bicycle pump is compressed by pushing in the handle. The inner diameter of the pump is 3.0 cm and the pump is depressed 20. cm with a pressure of 2.00 atm. (a) How much work is done in the compression? (b) Is the work positive or negative with respect to the air in the pump? (c) What is the...
- Fri Feb 12, 2021 3:45 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Temperature
- Replies: 7
- Views: 308
Re: Temperature
It is useful to look at a graph of phase change. The areas where the line is horizontal represent a constant temperature. This represents the time when all of the incoming heat is used to break intermolecular bonds, as opposed to raising the temperature of the substance.
- Fri Feb 12, 2021 3:43 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling #19
- Replies: 3
- Views: 156
Re: Sapling #19
In order to find Q, use the following equation where aA+bB --> cC+dD and P indicates partial pressure: (PCc)(PDd)/(PAa)(PBb). In this case, you would use PNH32/ PH23 PN2
- Fri Feb 12, 2021 3:37 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Using R in thermodynamic equations
- Replies: 24
- Views: 972
Re: Using R in thermodynamic equations
I write out all of the units in my calculations in order to determine which value of R to use. Depending on what units the equation already has and what units you need to cancel, you can then choose R accordingly. Sometimes it is easier to match your other units to R, such as converting an energy te...
- Fri Feb 12, 2021 3:34 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling Learning Week 5 and 6 Homework Question 19
- Replies: 5
- Views: 241
Re: Sapling Learning Week 5 and 6 Homework Question 19
Units may be the issue in this case. To solve, I converted all energy terms to Joules and all temperature terms to Kelvin so that they would cancel with R=8.314 J/Kmol. I then calculated Q using the equation (PNH3)^2/(PH2)^3 (PN2). Finally, I converted my final answer back to kJ as prompted by the a...
- Fri Feb 12, 2021 3:29 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Sapling week 5/6 question 18
- Replies: 8
- Views: 1875
Re: Sapling week 5/6 question 18
When I first did this problem, my issue was with the unites! Make sure that temperature is in Kelvins, and that you use the correct version of the gas constant (8.314 J/Kmol). Since the values for ∆Gº are given in kJ/mol, make sure you convert to J/mol so that the units cancel with the gas constant....
- Sat Feb 06, 2021 7:49 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Entropy = 0
- Replies: 6
- Views: 228
Re: Entropy = 0
I believe that any molecule with just a singular configuration (or distribution/arrangement/micro-state) will have an positional/residual entropy of 0. This includes diatomic molecules.
- Sat Feb 06, 2021 7:47 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: S = 0
- Replies: 21
- Views: 1127
Re: S = 0
I believe entropy=0 when there is only 1 structural configuration. For example, O2 gas only has 1 structural configuration and therefor has an entropy of 0.
- Sat Feb 06, 2021 7:42 pm
- Forum: Calculating Work of Expansion
- Topic: Is reversible expansion just theoretical?
- Replies: 11
- Views: 371
Re: Is reversible expansion just theoretical?
I believe that because nothing in reality is a perfect heat engine (all heat converted to work), calculating using equations for reversible expansion provides the maximum possible work.
- Sat Feb 06, 2021 7:39 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: How to know the sign for work
- Replies: 26
- Views: 891
Re: How to know the sign for work
I believe that you consider whether work is being done on the system (+) or whether the system is doing the work (-)
- Sat Feb 06, 2021 7:37 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chemistry Community Posts
- Replies: 17
- Views: 510
Re: Chemistry Community Posts
I think it might depend on your TA but I know last quarter as long as you had the correct number by the end of the quarter you would get full credit, even if from week to week you were missing posts.
- Tue Feb 02, 2021 8:24 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Tables
- Replies: 36
- Views: 1591
Re: ICE Tables
I believe that it is only dictated by the stoichiometric coefficient. It is during the 'E' row that molarity is taken into account.
- Thu Jan 28, 2021 12:49 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Heating a reaction at equilibrium
- Replies: 3
- Views: 71
Re: Heating a reaction at equilibrium
Thank you so much! I didn't even realize both K values were given that makes so much more sense!
- Thu Jan 28, 2021 12:31 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Heating a reaction at equilibrium
- Replies: 3
- Views: 71
Heating a reaction at equilibrium
Hello! In the following question from the textbook, how are we supposed to determine the effects of heating? I understand that the equation was initially heated in order to reach equilibrium, which leads me to believe that it is endothermic, and that heating an endothermic reaction favors the produc...
- Sun Jan 24, 2021 8:47 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Polyprotic Acids
- Replies: 5
- Views: 244
Re: Polyprotic Acids
Thanks everyone this really cleared it up!
- Sun Jan 24, 2021 5:52 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Polyprotic Acids
- Replies: 5
- Views: 244
Polyprotic Acids
Hello! I've seen a few posts about polyprotic acids that seem to provide differing responses. To clarify: - Can the first deprotenation of sulfuric acid be considered complete meaning you just calculate pH using calculations for a strong acid? The textbook says that the first deprotenation can be co...
- Sat Jan 23, 2021 8:36 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: How to fill in 2nd row of ICE table?
- Replies: 25
- Views: 740
Re: How to fill in 2nd row of ICE table?
If the reaction is proceeding from Reactants to Products, all of the reactants will have a -X value determined by stoichiometric coefficients, and all of the products will have a +X value determined by stoichiometric coefficients.
- Sat Jan 23, 2021 8:32 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Textbook Solutions Not Appearing
- Replies: 7
- Views: 175
Re: Textbook Solutions Not Appearing
This happened for a lot of people last quarter, and many people mentioned that downloading the "bookshelf" app for viewing the textbook fixed the problem!
- Sat Jan 23, 2021 8:31 pm
- Forum: Student Social/Study Group
- Topic: Calculators
- Replies: 52
- Views: 3064
Re: Calculators
I think any type of calculator is allowed, but it does not necessarily need to be graphing, as long as it can express scientific notation you should be set!
- Sat Jan 23, 2021 8:27 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Tables
- Replies: 36
- Views: 1591
Re: ICE Tables
Yes, I believe that the values of X correspond to the ratios between the stoichiometric coefficients, and you can decide the way in which to use these ratios.
- Sat Jan 23, 2021 8:25 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Temperature and K
- Replies: 2
- Views: 45
Re: Temperature and K
The textbook mentions that combustion reactions are always exothermic and reactions in the form X2(g)⇌2X(g), where X is a halogen is endothermic. Other than that, I think we most likely would have to be given more information
- Fri Jan 15, 2021 5:56 pm
- Forum: Administrative Questions and Class Announcements
- Topic: acids and bases on the midterm
- Replies: 6
- Views: 561
Re: acids and bases on the midterm
While I am not positive, I would assume after today's lecture that we are responsible for knowing weak vs strong acids and bases as the calculations depend on knowing whether or not an acid or base is fully dissociated. I would probably review the list of strong acids and bases and know concepts lik...
- Fri Jan 15, 2021 5:53 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: q and K
- Replies: 11
- Views: 280
Re: q and K
I believe that the difference between Q and K is only that Q is measured before the reaction has had adequate time to reach equilibrium whereas K is measured once the reaction has reached equilibrium. I do not think that they are necessarily measured at different temperatures. A value of K for a rea...
- Fri Jan 15, 2021 5:50 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: When x is negligible in Equilibrium constant
- Replies: 34
- Views: 1376
Re: When x is negligible in Equilibrium constant
As mentioned, K should be less than 10 -3 and ideally less than 10 -4 . If you want to check whether this approximation is valid, at the very end you can calculate percent ionization using the concentrations you calculated using the approximation. If the value for percent ionization is less than 5%,...
- Fri Jan 15, 2021 5:44 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Week 2 HW
- Replies: 8
- Views: 400
Re: Week 2 HW
Here is the derivation for how you can determine pH given pOH. You would not have to go through all of these steps in order to solve a problem, but it can be helpful to see why this calculation works! The ionization constant for water is Kw=[H 3 O + ][OH - }= 1x10 -14 knowing that log ab = log a + l...
- Sat Jan 09, 2021 1:21 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling Week 1&2 Homework Question
- Replies: 8
- Views: 445
Re: Sapling Week 1&2 Homework Question
What happens to a system at equilibrium when there is an increase in temperature? Will it favor products or reactants? Will Q be greater than, less than, or equal to K? I don't remember this from lecture. I don't think we covered it yet lol. But if you know, please let me know! Thank you :) I had a...
- Sat Jan 09, 2021 1:18 pm
- Forum: Ideal Gases
- Topic: PV=nRT and concentration
- Replies: 27
- Views: 1398
Re: PV=nRT and concentration
I found it useful to think of concentration in this case as Molarity. Molarity is calculated by taking the number of moles of a solute and dividing by the volume of the solution, or n/V. in the ideal gas law, solving for n/V is thereby solving for concentration.
- Sat Jan 09, 2021 1:16 pm
- Forum: Ideal Gases
- Topic: Kc vs Kp
- Replies: 109
- Views: 4369
Re: Kc vs Kp
The version of K used is dependent on how the value of K is calculated. If you used concentration of products and reactants to calculate K, then use Kc to denote this. If you used partial pressures to calculate K, them use Kp.
- Sat Jan 09, 2021 1:15 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K vs. Q
- Replies: 53
- Views: 1919
Re: K vs. Q
They are calculated the same way, however when calculating K the concentrations of product and reactants must be those at which the reaction is at equilibrium, whereas the concentrations of products and reactants used to calculate Q can be from any given point at which the reaction is occurring.
- Sat Jan 09, 2021 1:13 pm
- Forum: Ideal Gases
- Topic: T variable in pv=nrt [ENDORSED]
- Replies: 38
- Views: 1543
Re: T variable in pv=nrt [ENDORSED]
As people have mentioned, I would always use temperature in Kelvin as the alternative would be changing the units on the constants and pressure values. Its super simple to convert from Celsius to Kelvin if the temperature happens to be given in Celsius, all you have to do is take the temperature in ...
- Sat Dec 12, 2020 12:51 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Strong Bases
- Replies: 4
- Views: 330
Strong Bases
Hello! I am looking for some clarification on what classifies as a strong base. According to Sapling learning, only LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2 and Ba(OH)2 are strong bases. However, in the textbook as well as in lecture, group 1 and 2 oxides are listed as strong bases as well as G...
- Fri Dec 11, 2020 5:10 pm
- Forum: Lewis Structures
- Topic: HClO3 Lewis Structure [ENDORSED]
- Replies: 4
- Views: 1310
Re: HClO3 Lewis Structure [ENDORSED]
I believe that in non-metal acids, the Hydrogen is always attached to the Oxygen. This also applies to acids like Sulfuric acid, Nitric Acid, and phosphoric acid. You can confirm this increased stability using formal charge. If you want to look into this more, you can look up oxoacids which I believ...
- Fri Dec 11, 2020 5:07 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: Hard Water vs. Soft Water
- Replies: 9
- Views: 722
Re: Hard Water vs. Soft Water
from what I have learned in a class I am taking on water quality, hard water is more alkaline due to the presence of cations (like Fe 2+ or Mg 2+ ).In the lecture Dr. Lavelle mentioned that alkaline materials have a soapy feel so it seems like maybe hard water would have this soapy feel since it is ...
- Fri Dec 11, 2020 4:58 pm
- Forum: Air Pollution & Acid Rain
- Topic: pH of hard water
- Replies: 4
- Views: 339
Re: pH of hard water
From what I have learned in other classes about water quality, hard water is more alkaline and has to do with the presence of multivalent metallic cations. Soft water is more acidic.
- Fri Dec 11, 2020 4:53 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Chelating Ligands vs Polydentate ligands
- Replies: 5
- Views: 448
Re: Chelating Ligands vs Polydentate ligands
A polydentate ligand is chelating ligand. I believe that chelating just refers to the structure that is able to form in the presence of a polydentate ligand.
- Fri Dec 11, 2020 4:51 pm
- Forum: Naming
- Topic: "ate" and "ic"
- Replies: 4
- Views: 589
Re: "ate" and "ic"
Not sure if you are referring to naming coordination compounds, but here are the rules for using ate in these compounds: I believe that you use 'ate-' on the metal when the entire coordination compound has a negative charge. For example [Co(CN) 2 (OH 2 )] 2- has an overall charge of negative 2, so i...
Re: Naming
Does anyone know if theres a list of what must be memorized in naming?
- Sat Dec 05, 2020 3:07 pm
- Forum: Lewis Structures
- Topic: Most Stable Structure
- Replies: 23
- Views: 3459
Re: Most Stable Structure
I believe you would attempt to minimize the formal charge, and this often does take trial and error of drawing lewis structures. You can also consider how many bonds and lone pairs an atom would need to have a formal charge of zero and then try to form the lewis structure this way.
- Sat Dec 05, 2020 3:04 pm
- Forum: Lewis Structures
- Topic: Lone Pair placement
- Replies: 10
- Views: 595
Re: Lone Pair placement
I believe it depends on whether you are drawing a lewis structure or trying to represent the shape. In a lewis structure, I think all that matters is the correct bonds, atoms, and lone pairs so placement of lone pairs wouldn't matter.
- Sat Dec 05, 2020 2:59 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: pH formula?
- Replies: 69
- Views: 3563
Re: pH formula?
Professor Lavelle mentioned that when you see 'p' in chemistry it means take the negative log. So 'pH' means to take the negative log of the species with H+, or H3O+
- Sat Dec 05, 2020 2:53 pm
- Forum: Naming
- Topic: Order of Ligands/naming
- Replies: 28
- Views: 1115
Re: Order of Ligands/naming
As previously mentioned, they are listed alphabetically excluding the prefix. For example 'pentaamine' comes before 'chloro' because you reference the a in amine and not the p in penta
- Sat Nov 28, 2020 6:00 pm
- Forum: Student Social/Study Group
- Topic: Midterm/Final Success?
- Replies: 17
- Views: 761
Re: Midterm/Final Success?
I have found the textbook reading and questions to be extremely helpful. I watch all of the lectures first, and take notes on them, and then in the few days before the test I do every assigned problem and read through the textbook. The textbook is great for reinforcing what we learned in lecture, bu...
- Sat Nov 28, 2020 5:56 pm
- Forum: Sigma & Pi Bonds
- Topic: sapling #15
- Replies: 24
- Views: 1063
Re: sapling #15
A single bond is a sigma bond. A double bond has one sigma bond and one pi bond. A triple has one sigma bond and two pi bonds.
- Sat Nov 28, 2020 5:54 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: H2O VSEPR
- Replies: 27
- Views: 1210
Re: H2O VSEPR
A molecule with 4 regions of electron density, 2 lone pairs, and 2 bonding pairs, is bent. However, I believe that this could be characterized as having tetrahedral arrangement of electron density.
- Sat Nov 28, 2020 5:41 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sapling #17
- Replies: 2
- Views: 167
Re: Sapling #17
I may be wrong, but I believe that the 60º angle comes from the structure in which the three carbons form a triangle-shape. Since the angles of a triangle add up to 180º, each angle between carbons in this structure should be around 60º.
- Sat Nov 28, 2020 5:36 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma and Pi Bonds
- Replies: 9
- Views: 818
Re: Sigma and Pi Bonds
A single bond is a sigma bond. Each subsequent bond (2nd, third, etc) is a pi bond. If you have a double bond, for example, one of the bonds is a sigma bond in the other is a pi bond. If you have a triple bond, one of the bonds is a sigma bond and the other two are pi bonds. I don't believe that you...
- Sun Nov 22, 2020 1:48 pm
- Forum: Octet Exceptions
- Topic: Expanded Octets
- Replies: 11
- Views: 567
Re: Expanded Octets
They can be expanded further! For example, when Xe bonds with 4 fluorine atoms, it can make 4 single bonds and have 2 lone pairs and still have a formal charge of zero, giving it 12 valence electrons! (4 bonds+2 lone pairs= 8, 8-8=0). A lot of the time I like to think about expanded octets in terms ...
- Sun Nov 22, 2020 1:40 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Overlapping Orbitals
- Replies: 3
- Views: 75
Re: Overlapping Orbitals
If you have a single bond, it is a sigma bond. If you have a double bond, one is a sigma bond and one is a pi bond. If you have a triple bond, one of the bonds is a sigma bond and the other two are pi bonds.
- Sun Nov 22, 2020 1:38 pm
- Forum: Hybridization
- Topic: Double bonds structures
- Replies: 5
- Views: 278
Re: Double bonds structures
To answer the question about triple bonds, if the bond includes a pi bond then it is locked (ie it cannot rotate). A molecule with a triple bond has one sigma bond and two pi bonds, and therefore it cannot rotate.
- Sun Nov 22, 2020 1:34 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chem 14B Enrollment
- Replies: 27
- Views: 1627
Re: Chem 14B Enrollment
This is from Professor Lavelle's website under enrollment questions; 'I play no administrative role. In other words I play no role in determining the size, venue or number of times a first-year chemistry course is offered and I cannot help with class or discussion section enrollment questions. I als...
- Sun Nov 22, 2020 1:27 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Molecular Shape Polarity
- Replies: 3
- Views: 80
Re: Molecular Shape Polarity
It depends on if the arrangement of atoms surrounding the central atom (are they all the same?). Then, depending on how these atoms are arranged and whether the dipole moments of these atoms cancel, you can determine whether it is polar or non polar.
- Sun Nov 15, 2020 12:31 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Memorizing the Different Shapes
- Replies: 4
- Views: 213
Re: Memorizing the Different Shapes
I believe that we are expected to know how to figure out the shape based on the lewis structure and the rules for VESPR. This would involve memorizing the names of the shapes, their bond angles, and the basic rules for figuring out how a molecule will be shaped.
- Sun Nov 15, 2020 12:29 pm
- Forum: Formal Charge and Oxidation Numbers
- Topic: Clarification
- Replies: 8
- Views: 386
Re: Clarification
Yes, I believe that the formal charges of individual atoms should add up to the overall charge of the molecule, which is seen both in the chemical formula (ie CO32- which would have an overall 2- charge, and in the lewis structure as you mentioned.
- Sun Nov 15, 2020 12:18 pm
- Forum: Student Social/Study Group
- Topic: Online textbook answer key
- Replies: 6
- Views: 558
Re: Online textbook answer key
I have this problem too with many questions not loading. I would suggest possibly downloading the bookshelf app as professor mentioned in his latest email and trying to view it that way as it requires downloading the entire book.
- Sun Nov 15, 2020 12:14 pm
- Forum: Ionic & Covalent Bonds
- Topic: Electronegativity
- Replies: 18
- Views: 619
Re: Electronegativity
I believe that we don't have to memorize it and if we needed to do a calculation the values would be provided. You should just know the general trend on the periodic table and why this is!
- Sun Nov 15, 2020 12:12 pm
- Forum: Lewis Structures
- Topic: Drawing Lewis Structures on Midterm
- Replies: 31
- Views: 1021
Re: Drawing Lewis Structures on Midterm
Since it is multiple choice, I would expect that we would have to choose the diagram with formal charge minimized.
- Sat Nov 07, 2020 2:53 pm
- Forum: Ionic & Covalent Bonds
- Topic: Formal Charge Equation
- Replies: 10
- Views: 440
Re: Formal Charge Equation
This doesn't conceptionally explain it, but a friend suggested that for formal charge you should just count the number of items drawn around each element. For example, for an element which is connected to a double charge and 2 lone pairs (which is 4 dots), the formal charge would be 6 (2 lines+4 dot...
- Sat Nov 07, 2020 2:49 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Isoelectric atoms
- Replies: 9
- Views: 604
Re: Isoelectric atoms
The charges are not the same, isoelectronic just refers to atoms with the same number of electrons! For example, when elements like B, C, O, or F gain electrons in order to get an octet, they all have the same number of electrons as Neon, therefore B,C,O,F and Ne would be isoelectronic.
- Sat Nov 07, 2020 2:42 pm
- Forum: Lewis Structures
- Topic: Negative Sign
- Replies: 12
- Views: 809
Re: Negative Sign
The number on the outside is the overall charge of the molecule. This has to do with the total number of electrons present versus the expected number present from the elements. The numbers next to the individual atoms is the formal charge, and the sum of all of these formal charges is equal to the n...
- Sat Nov 07, 2020 2:40 pm
- Forum: Resonance Structures
- Topic: Resonant Structures and Formal Charge
- Replies: 3
- Views: 119
Re: Resonant Structures and Formal Charge
I believe you usually try to minimize the formal charge (get it closest to 0) for the most electronegative element.
- Sat Nov 07, 2020 2:39 pm
- Forum: Lewis Structures
- Topic: lewis structure
- Replies: 17
- Views: 567
Re: lewis structure
It's dependent on whether the number of electrons in the diagram is more or less than the number of expected electrons from the elements present. For example, if the number of electrons expected from the elements present is 26, but only 25 are present in the lewis structure, the diagram would have a...
- Wed Nov 04, 2020 1:10 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Posts for Chem Community & receiving credit
- Replies: 5
- Views: 188
Re: Posts for Chem Community & receiving credit
I believe according to his email, the first sum of posts will be calculated this Thursday, so you should have 20 posts by this Thursday.
- Thu Oct 29, 2020 7:11 pm
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Rydberg Equation
- Replies: 9
- Views: 282
Re: Rydberg Equation
I believe that you can always use the smaller n (ie n=1) value as n1 and the larger value as n2 (ie n=6), and then figure out the sign at the end depending on if light was emitted or absorbed.
- Thu Oct 29, 2020 7:06 pm
- Forum: Heisenberg Indeterminacy (Uncertainty) Equation
- Topic: Module Question #23
- Replies: 4
- Views: 207
Re: Module Question #23
I did the same thing originally, and when a question uses +/- for uncertainty, I find it easier to apply this to a number. For example, if you apply +/-5 to 10, you get 15 and 5. Here, it is easier to see that the range in position is 10 units, and not 5.
- Thu Oct 29, 2020 7:02 pm
- Forum: Photoelectric Effect
- Topic: Post-Module Assessment #28
- Replies: 2
- Views: 125
Re: Post-Module Assessment #28
The mass of an electron is provided on the equation sheet
- Thu Oct 29, 2020 6:59 pm
- Forum: DeBroglie Equation
- Topic: Sapling HW #14
- Replies: 7
- Views: 379
Re: Sapling HW #14
everything should match the units of h (kgm^2/s)
if a value isn't in kg, m, or seconds, you should convert it!
if a value isn't in kg, m, or seconds, you should convert it!
- Thu Oct 29, 2020 6:53 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Rydberg constant
- Replies: 7
- Views: 626
Re: Rydberg constant
Im pretty sure thats just R/c, which allowed you to set the equation equal to 1/wavelength
- Sat Oct 24, 2020 8:17 pm
- Forum: Student Social/Study Group
- Topic: Chem Community Questions
- Replies: 8
- Views: 776
Re: Chem Community Questions
5 posts are due every Sunday night before midnight :)
- Sat Oct 24, 2020 8:04 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbitals
- Replies: 6
- Views: 309
Re: Orbitals
I believe that he was demonstrating that the upper bound of l is n-1. It can take on any possible values from 0 to n-1, with n-1 being the upper bound value. I don't think that if n=2 l could equal 1, but it could equal 0 or 1. This is a chart that I used to better understand it. When n=3, l can hav...
- Sat Oct 24, 2020 7:06 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Molar Mass and Metal/Sulfides
- Replies: 8
- Views: 7844
Re: Molar Mass and Metal/Sulfides
Basically, this question wants you to solve for the molar mass of 'M' and identify it by finding the correct element on the periodic table with this molar mass. You do this by subtracting the molar mass of the known elements from the total molar mass. Looking at the periodic table, M is revealed to ...
- Sat Oct 24, 2020 6:56 pm
- Forum: DeBroglie Equation
- Topic: Sapling Week 2-4 HW Question 24
- Replies: 11
- Views: 519
Re: Sapling Week 2-4 HW Question 24
I believe that the first and second waves in the right column would work! Basically, if you repeated this same wave segment where the previous wave segment ended, it should create a continuous wave. Because the first and the second waves create a pattern in which the last iteration of the wave could...
- Sat Oct 24, 2020 6:48 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Calculator
- Replies: 3
- Views: 101
Re: Calculator
In discussion, my TA said any type of calculator should be fine!
- Fri Oct 16, 2020 4:54 pm
- Forum: Properties of Electrons
- Topic: Wave Properties of Electrons
- Replies: 4
- Views: 97
Re: Wave Properties of Electrons
This isn't exactly the same concept but its how I visualize it: Imagine you are holding a rope and moving it in a wave pattern. If someone stands on the other side of the rope and creates their own wave, there are essentially 2 possible outcomes: 1. when their wave reaches your wave, the two waves c...
- Fri Oct 16, 2020 4:37 pm
- Forum: Significant Figures
- Topic: SIG FIGS
- Replies: 13
- Views: 609
Re: SIG FIGS
There are rules for SIG FIGS depending on what kinds of calculations you are doing. For addition and subtraction, usually precision matches the lowest number of decimal places of any number given. For multiplication and division, typically you match the number of sigfigs of the least precice number....
- Fri Oct 16, 2020 4:31 pm
- Forum: Einstein Equation
- Topic: wave vs. photons
- Replies: 4
- Views: 245
Re: wave vs. photons
He mentioned that anything at the quantum level elicits some wave-like properties. Like with light, electrons have some properties that are best described using a particle model. In the experiments discussed last week, the particle model was best suited to describing the properties of electrons. How...
- Fri Oct 16, 2020 4:22 pm
- Forum: Properties of Light
- Topic: Light Having wave and photoelectric properties
- Replies: 3
- Views: 199
Re: Light Having wave and photoelectric properties
The photoelectric effect is important because it demonstrates that light cannot be modeled only as a wave. In a wave-only model of light, increasing the amplitude of the wave should increase the energy. With this assumption, adequately increasing the 'intensity' of the light should allow an electron...
- Fri Oct 16, 2020 4:13 pm
- Forum: Empirical & Molecular Formulas
- Topic: Empirical and Molecular Formulas
- Replies: 9
- Views: 827
Re: Empirical and Molecular Formulas
The ratios of elements are the same, however, the multiples are different. Empirical equations are the simplest, whole number ratios of atoms, whereas Molecular formulas take into account the compound's molar mass and appear as a multiple of the empirical formula. These formulas can be the same if t...
- Fri Oct 09, 2020 2:56 pm
- Forum: Balancing Chemical Reactions
- Topic: Balancing Chemical Reactions Order
- Replies: 49
- Views: 5607
Re: Balancing Chemical Reactions Order
It's often easiest to begin with an element that does not become split up in the products!
For example, in
C5H12 + O2 --> CO2 + H2O it is easiest to NOT begin with oxygen, as this element appears in both products! In this case, I would probably start with C, followed by H, and then assessing O.
For example, in
C5H12 + O2 --> CO2 + H2O it is easiest to NOT begin with oxygen, as this element appears in both products! In this case, I would probably start with C, followed by H, and then assessing O.