Search found 102 matches
- Sun Mar 14, 2021 1:02 pm
- Forum: First Order Reactions
- Topic: Half-life independent from initial concentration
- Replies: 8
- Views: 1651
Re: Half-life independent from initial concentration
I had the same question, but it just has to do with the concentrations cancelling. They don't end up appearing in the equation visibly, but the concentration is accounted for in k! So you just don't have to factor the initial concentration in again in first order but it is still technically accounte...
- Sun Mar 14, 2021 12:59 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Order of Reactants
- Replies: 6
- Views: 462
Re: Order of Reactants
You can't determine the order just by the chemical equation, so that would be an indicator that you'd need more information!
- Sun Mar 14, 2021 12:57 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: finding "n"
- Replies: 12
- Views: 857
Re: finding "n"
Yes, so the "number" and moles are going to be the same thing, it's the coefficient next to the electron, but it has to be taken from the balanced reaction instead of the half equations.
- Sun Mar 14, 2021 12:55 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Effect of catalyst
- Replies: 22
- Views: 2453
Re: Effect of catalyst
Delta H does not have to do with the activation energy, but rather it is the change in enthalpy from the reactants to products in the most direct path on the graph (excluding the hump). So it's the net, and therefore the activation energy does not affect it. Because the catalyst lowers the activatio...
- Sun Mar 14, 2021 12:53 pm
- Forum: Environment, Ozone, CFCs
- Topic: catalysis vs intermediate
- Replies: 25
- Views: 2045
Re: catalysis vs intermediate
An intermediate is produced and then consumed, while a catalyst is consumed and then produced.
- Sat Mar 06, 2021 3:29 pm
- Forum: General Rate Laws
- Topic: 7.C.7
- Replies: 2
- Views: 220
Re: 7.C.7
The rate of your reaction is going to be dependent on the reactants, so because your equation has coefficients of 1 for NO and Br2, they should both only be raised to the first power in the rate equation.
- Sat Mar 06, 2021 3:25 pm
- Forum: Student Social/Study Group
- Topic: Note Taking
- Replies: 145
- Views: 17532
Re: Note Taking
I handwrite my notes for every class because I find that it is much easier to go back and flip through them (specifically for this class) when doing homework, plus it makes it more efficient when you're trying to draw graphs or charts. I try to take notes on the main points of lectures and specific ...
- Sat Mar 06, 2021 3:22 pm
- Forum: Second Order Reactions
- Topic: Sapling #4 WK 9/10
- Replies: 9
- Views: 4198
Re: Sapling #4 WK 9/10
Someone also explained it to me that you want to look at k as the factor that will be used to cancel out any of the units that are skewed by the order of the reaction so that the final answer will always be M/s. So whenever you are given one of these, it's helpful to look at what units are present a...
- Sat Mar 06, 2021 3:19 pm
- Forum: Zero Order Reactions
- Topic: Zero order
- Replies: 8
- Views: 689
Re: Zero order
^ like the post above mentions, this is applied a lot to enzymes! In the microbio course I'm in right now we're studying enzyme kinetics and zero order reactions occur when the rate is directly proportional to the concentration of the substrate, while the rate therefore has nothing to do with the ac...
- Sat Mar 06, 2021 3:13 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Do you ever multiply E?
- Replies: 3
- Views: 1604
Do you ever multiply E?
I'm still very confused on whether you multiply Ered ever when you're calculating the standard cell potential of a reaction. I thought you had to multiply Ered to match the stoichiometric coefficients/whatever corresponds to cancelling out the electrons, but then in a homework problem I attempted li...
- Sun Feb 28, 2021 9:55 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling 7&8 #5
- Replies: 4
- Views: 360
Re: Sapling 7&8 #5
It looks to me like you may have skipped out on electrons in the sulfur equation or something. I had the same question setup and the answer is 2Mno4- + 3S2- + 4H2O --> 2MnO2 + 8OH- + 3S Remember that the oxidation of S 2- involves the transfer of 2 electrons, while the reduction of MnO4- involves th...
- Sun Feb 28, 2021 9:44 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Standard Reaction Potentials
- Replies: 3
- Views: 247
Re: Standard Reaction Potentials
I've been wondering this too! Someone said something about it being an property so the coefficients don't matter or something... but I would really appreciate if someone could use an example to show it!
- Sun Feb 28, 2021 9:41 pm
- Forum: Balancing Redox Reactions
- Topic: hw #3
- Replies: 3
- Views: 276
Re: hw #3
I would check to make sure if it was done in a basic or an acidic solution, since this will affect whether you're allowed to have OH- left over.
- Sun Feb 28, 2021 9:28 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: sapling week 8 #15
- Replies: 4
- Views: 284
Re: sapling week 8 #15
arisawaters2D wrote:Do coefficients matter when calculating Q?
Yes coefficients do matter when calculating Q! They become the exponent that the concentration value is raised to.
- Sun Feb 28, 2021 9:27 pm
- Forum: General Science Questions
- Topic: Midterm 2 Reactions
- Replies: 79
- Views: 6699
Re: Midterm 2 Reactions
I didn't know the grades were out, are they on myUCLA? Mine isn't there. Either way, with midterm 2 I was a bit surprised by the amount of conceptual questions and I feel like that means there will probably be more questions on the final that cover midterm 2 calculations.
- Sat Feb 20, 2021 8:17 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: anode and cathode L/R
- Replies: 14
- Views: 692
Re: anode and cathode L/R
I think what is important is that in a drawn diagram (as opposed to the cell diagram with lines) the anode and cathode may not always be oriented left to right, however in a cell diagram with lines they should ALWAYS be oriented anode on left and cathode on right. So if, for example, you were given ...
- Sat Feb 20, 2021 8:13 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Which side to put the electrode on a cell diagram
- Replies: 4
- Views: 352
Re: Which side to put the electrode on a cell diagram
I'm pretty sure both the cathode and the anode are considered to have an electrode that is initiating the electron transfer, so both sides should acknowledge what is being used to transfer electrons.
- Sat Feb 20, 2021 8:10 pm
- Forum: Balancing Redox Reactions
- Topic: Oxidation Numbers
- Replies: 9
- Views: 611
Re: Oxidation Numbers
The appendix from the book is also pretty useful when it comes to deciphering all the rules! https://sites.google.com/site/chempendix/oxidation
- Sat Feb 20, 2021 8:09 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Half Reaction Standard Reduction Potential
- Replies: 4
- Views: 283
Re: Half Reaction Standard Reduction Potential
Yeah, I believe that the standard potentials have to be given to us. We will probably be able to calculate them if he ends up giving us equations that incorporate other functions of reactions, but not at the moment at least.
- Sat Feb 20, 2021 7:31 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling week 7 #7
- Replies: 3
- Views: 331
Re: Sapling week 7 #7
Apparently there is a specific order that the shorthand notation should be written in, in terms of which order the phases are in contact. The Pb/Ag anode and cathode should be on the far left and far right, adjacent to the PbCl 2 and AgCl. The two Cl - s are then placed by the double vertical line,...
- Sat Feb 20, 2021 6:54 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling week 7 #7
- Replies: 3
- Views: 331
Sapling week 7 #7
Hi, I have attempted this question so many times and I can't figure out what I'm doing wrong. I've tried just about everything, at the beginning sapling kept telling me "the cathode should occupy the right‑hand position of the line diagram." and then I moved something and it started saying...
- Wed Feb 10, 2021 5:48 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling Week 5/6 #12
- Replies: 4
- Views: 302
Re: Sapling Week 5/6 #12
Hi! Here is a super useful chart for this concept. Screen Shot 2021-02-10 at 2.24.49 PM.png The bottom two rows explore the temperature-dependent scenarios for Gibbs free energy. In these scenarios, a temperature can be above or below (or at, if in equilibrium and delta G is 0) a certain point of mu...
- Wed Feb 10, 2021 5:37 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Thermo Equilibrium
- Replies: 4
- Views: 301
Re: Thermo Equilibrium
Hi! I'm pretty sure thermal equilibrium just refers to the state at which all components of the system possess the same amount of thermal energy, so there is no net exchange of thermal energy between them. They could still exchange energy, but not to facilitate a net gain or loss.
- Wed Feb 10, 2021 5:28 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling HW 5/6 #20 G v. Progress of rxn graph
- Replies: 2
- Views: 188
Re: Sapling HW 5/6 #20 G v. Progress of rxn graph
Hi! The "spontaneous" labels go with the arrows on top, while the "Q<K" and "Q>K" labels go on the bottom spaces. You have it all correct. Q<K is spontaneous forward and Q>K is spontaneous reversely, while Q=K is when the reaction is at equilibrium.
- Wed Feb 10, 2021 5:21 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Different Positions in Entropy
- Replies: 7
- Views: 360
Re: Different Positions in Entropy
I find this concept kind of confusing too. Based on my understanding, I think we are looking at it theoretically within a given state of matter. I think the number of possible microstates (degeneracy) has to do with the number/identities of different atoms (since this determines the number of possib...
- Wed Feb 10, 2021 5:03 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling Week 5/6 #14
- Replies: 1
- Views: 99
Re: Sapling Week 5/6 #14
Hi! The answer is that you actually are using deltaS = deltaH/(T). Using deltaS = deltaH/(T) will give you the same answer because at equilibrium, deltaG is 0. So I think this question wanted us to make the connection between the two equations by using the Gibbs free energy equation. deltaG = deltaH...
- Sun Feb 07, 2021 6:39 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Sapling #18
- Replies: 4
- Views: 258
Re: Sapling #18
Hi! After calculating q I wrote the equation deltaU = q +w, and that w = -PextdeltaV Knowing I would need the final and initial volumes, I used the ideal gas equation two separate times to generate the final and initial volume values based on the values provided in the question. Then, I used those t...
- Sun Feb 07, 2021 6:34 pm
- Forum: Calculating Work of Expansion
- Topic: Sapling 15
- Replies: 6
- Views: 606
Re: Sapling 15
Hi! I first converted the mass of NaN3 to moles because that is the only thing that the question provides a mass for. Then, I used stoichiometric coefficients to get to what I was looking for: the moles of N2. I did this by multiplying the moles of NaN3 by 3/2, because that is the ratio of N2 to NaN...
- Sun Feb 07, 2021 6:27 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: HW 10
- Replies: 5
- Views: 164
Re: HW 10
Hi! You can find q by using the equation q = nCsubS*deltaT, but because what we are looking for is the final temperature, we manipulate the equation to show final temperature as a variable. The problem involves changes of state, so you want your equation to show that heat to melt ice + heat to bring...
- Sun Feb 07, 2021 6:14 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Sapling #19
- Replies: 6
- Views: 332
Re: Sapling #19
Yeah, the question says the calorimeter was calibrated by carrying out a reaction known to release heat and then gives you the negative q of that reaction. When you calculate the heat capacity of the calorimeter, you're using that q without the negative sign because heat capacity is always positive,...
- Sun Feb 07, 2021 6:05 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: Sapling 17
- Replies: 2
- Views: 369
Re: Sapling 17
I like the explanation above! I also find that it helps to work backwards in terms of making it easier to understand, at least when you first start doing these problems. So you know deltaU is 7545 J, which means that 7545J = -346J + q It looks like you tried to use 16000c as a sub for q to get C fro...
- Sun Jan 31, 2021 2:16 am
- Forum: Calculating Work of Expansion
- Topic: Sapling 15
- Replies: 2
- Views: 318
Re: Sapling 15
I think the explanation above is really good! Sometimes with these problems it can be hard to figure out what you're looking for, but I just try to focus on the variable that it's asking for and the variables that I already have. For this question they only give you grams of NaN3, but you're looking...
- Sun Jan 31, 2021 2:05 am
- Forum: Calculating Work of Expansion
- Topic: Sapling HW Week 3/4 #15
- Replies: 3
- Views: 3568
Re: Sapling HW Week 3/4 #15
I started by converting the mass of NaN3 to moles. The reason you want to do this is because NaN3 is the only compound for which you're given a mass -- it's important to mention that what you're ultimately looking for is the quantity of N2, so if the problem gave you the mass of N2, you would just g...
- Sun Jan 31, 2021 1:50 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Calculating standard enthalpy of formation clarification
- Replies: 7
- Views: 385
Re: Calculating standard enthalpy of formation clarification
what's the difference between standard enthalpy of formation and standard enthalpy of a reaction? Standard enthalpy of formation is the kj/mol quantity for the formation of an element/compound, but the standard enthalpy of a reaction is the kj or J value of the entire reaction, which includes react...
- Sun Jan 31, 2021 1:44 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Standard Enthalpies of Formation using Hess's Law
- Replies: 18
- Views: 1134
Re: Standard Enthalpies of Formation using Hess's Law
You can rearrange the equation as long as you account for sign changes. Typically with Hess's law problems they give you a few different reactions and the enthalpies of those reactions, and you might also be given the standard enthalpy of formation of one/some of the molecules. So if you're rearrang...
- Sat Jan 30, 2021 11:36 pm
- Forum: Calculating Work of Expansion
- Topic: week 4 Sapling #14 reversible vs irreversible
- Replies: 1
- Views: 138
week 4 Sapling #14 reversible vs irreversible
Hi, in the book example 4A.2, it says that "Provided the initial and final states are the same, a change carried out reversibly always does more work than a change carried out irreversibly, so you should expect the second path to produce more work and therefore correspond to a more negative val...
- Sun Jan 24, 2021 2:35 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Homework number six
- Replies: 4
- Views: 256
Re: Homework number six
This was really hard for me too, but I find it helps to visualize what is actually happening when you put it in water. If you use the charts in the book that someone mentioned above, you'll be able to see the character of the cations and anions when they're in water. If the anion is from a weak acid...
- Sun Jan 24, 2021 2:25 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: ICE Tables
- Replies: 36
- Views: 1946
Re: ICE Tables
The numbers next to Xs are just the coefficients and do not have to do with the molarity. Molarity is the concentration, which you end up plugging in later.
- Sun Jan 24, 2021 2:21 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Enthalpy and equilibrium
- Replies: 1
- Views: 93
Enthalpy and equilibrium
The other day I was in Justin's step-up session and he asked a question about equilibrium that didn't mention delta H at all, but then the entire mode of solving it was around delta H? Can someone explain the relationship between enthalpy and equilibrium and what the implications could be if there i...
- Sun Jan 24, 2021 2:12 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Sapling Week 3&4 HW #10
- Replies: 1
- Views: 85
Re: Sapling Week 3&4 HW #10
Hi! It looks like my problem has different values for the masses which is strange but otherwise it's the same question. I used the word equation from the hint and then plugged in the formulas corresponding to what it was describing. So for "heat to melt ice" I used deltaHf which is 333.6J/...
- Sun Jan 24, 2021 1:34 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Sapling Week 3 #9
- Replies: 4
- Views: 173
Sapling Week 3 #9
Hi! I was wondering if someone could help me understand how to do this problem, I've been able to do all the problems fine until #9 and I have no idea where to even begin with it, I looked in the book and it didn't help me. "If you combine 300.0 mL of water at 25.00 ∘C and 130.0 mL of water at ...
- Fri Jan 15, 2021 5:36 pm
- Forum: Student Social/Study Group
- Topic: Approaching Outlines
- Replies: 14
- Views: 749
Re: Approaching Outlines
Hi! I know everyone has their own way of doing things, but I personally will go over the outline at the end of the section and look at the textbook problems at the end of the week. If there are things we didn't cover in lecture/homework, people will usually ask about them on chemistry community or i...
- Fri Jan 15, 2021 5:31 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Week 2 HW
- Replies: 8
- Views: 477
Re: Week 2 HW
You can subtract the pH from 14 to get the pOH. Then you can do 10^(-pOH) to get [OH-]
- Fri Jan 15, 2021 5:28 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Predominant Species
- Replies: 3
- Views: 259
Re: Predominant Species
Hi! To do this, you have to look at how the pH compares to the pKa. For acids, if the pH is higher (more basic) than the pKa, then the charged, deprotonated species of A− will become more predominant in solution. If the pH is lower (more acidic) than the pKa, the neutral, protonated species of HA wi...
- Fri Jan 15, 2021 5:22 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Strong Acid and Base
- Replies: 4
- Views: 271
Re: Strong Acid and Base
Hi! I am not sure what you mean by writing a new equation or making a second ICE table, typically there should just be one for these problems. But aside from that, when dissociation occurs, it means that the strong acid or base completely separates into its ions when it is in water. Therefore, H+ (f...
- Fri Jan 15, 2021 5:08 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling Week 1 #9
- Replies: 3
- Views: 197
Re: Sapling Week 1 #9
My ICE table was initial: N2 [.3] O2 [.3] 2NO [.8] change: N2 [+x] O2 [+x] 2NO [-2x] equilibrium: N2 [.3+x] O2 [.3+x] 2NO [.8-2x] The wording of these questions can be tricky and confusing, but I find it helps to focus on figuring out what the question is asking, which in this case is, what is the c...
- Sun Jan 10, 2021 7:36 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling #10
- Replies: 2
- Views: 171
Re: Sapling #10
If you were able to use your x value to calculate the equilibrium concentration of NO2 you're probably on the right track. Because NO2 is 2.87-2x, but N2O4 is 3.11+x, did you make sure to add x (as opposed to subtract x and/or 2x)? Hope this helps or you're able to find the issue!
- Sun Jan 10, 2021 7:32 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling number 6 Week 1
- Replies: 3
- Views: 200
Re: Sapling number 6 Week 1
Hi! I first calculated Q by plugging in the concentrations to [NH3]^2/[N2][H2]^3. Then I compared Q to K to answer the second part.
- Sun Jan 10, 2021 7:27 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Week 1 Assignment
- Replies: 17
- Views: 757
Re: Week 1 Assignment
Hi! Sapling problems are considered separate from "textbook problems," the textbook problems are the book problems recommended by Lavelle in the outlines, doing them won't get you points but he includes textbook problems on exams and they're good practice. Sapling is required (if you want ...
- Sun Jan 10, 2021 7:23 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 5G.1
- Replies: 4
- Views: 229
Re: 5G.1
Yeah Q would be affected, I think to know if it would increase or decrease you have to know which side has more moles but I may be wrong.
- Sun Jan 10, 2021 7:13 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling #7
- Replies: 3
- Views: 206
Re: Sapling #7
Hi! My understanding is that when you have an endothermic reaction, composition shifts towards the products resulting in an increase in heat absorption that helps offset the increase in temperature. K increases in endothermic reactions, but the addition of heat is not going to make Q decrease becaus...
- Sun Dec 13, 2020 7:25 am
- Forum: Bronsted Acids & Bases
- Topic: Sapling Week 10 #2
- Replies: 7
- Views: 583
Re: Sapling Week 10 #2
An amphoteric substance must have - hydrogen present (so it can act as a Bronsted acid to donate H+) - a feature that allows it to accept an H+ (typically this feature is a negative charge) so it can act as a Bronsted base So by looking at the formulas and seeing if they fit those bullet points, you...
- Sun Dec 13, 2020 7:10 am
- Forum: Acidity & Basicity Constants and The Conjugate Seesaw
- Topic: Textbook problem 6C.17
- Replies: 4
- Views: 284
Re: Textbook problem 6C.17
From what I know, since C17H19O3N has a N with a lone pair of electrons, it would be an ammine. Ammines are generally considered weak bases. BrO- is the conjugate base of HBrO, a weak acid. Therefore, it would most likely be considered a stronger base than morphine (the weaker the acid, the stronge...
- Sun Dec 13, 2020 6:59 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: polydentate ligands
- Replies: 5
- Views: 488
Re: polydentate ligands
I agree, I think just make sure you are familiar with the sheet from the website and know what the prefixes mean. I assume that the examples of terms you used in your question will be defined on the final if they are included since that is not emphasized on the outline/in lectures.
- Sun Dec 13, 2020 6:53 am
- Forum: Determining Molecular Shape (VSEPR)
- Topic: 5 regions as a linear shape
- Replies: 3
- Views: 215
Re: 5 regions as a linear shape
Although XeF2 has 3 electron pairs because it is arranged symmetrically around Xe, so the bond angles will still be 180 degrees, making the molecule linear. Do the lone pairs not count in the bond angle? And I am assuming the 180 is between the bond of Xe and F, what happens to the lone pairs and w...
- Sun Dec 13, 2020 6:48 am
- Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
- Topic: bond type for Resonance structure
- Replies: 1
- Views: 205
Re: bond type for Resonance structure
Hi! So SO2 has 3 possible structures, one has 2 double bonds (one between Sulfur and each oxygen) and the other two have a double bond between sulfur and one oxygen and a single bond between sulfur and the other oxygen. Since the second two structures are essentially mirrors of each other they have ...
- Sun Dec 06, 2020 11:46 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Complex ion
- Replies: 3
- Views: 196
Re: Complex ion
I think coordination compound is an umbrella term for a central atom surrounded by ligands, if it does not have a net charge then it is neutral and if it has a net charge then it is a complex ion.
- Sun Dec 06, 2020 11:36 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination Number
- Replies: 4
- Views: 309
Re: Coordination Number
^ and to elaborate, bidentate means that the ligand has two atoms that coordinate to the central atom, as opposed to one, which would be monodentate.
- Sun Dec 06, 2020 11:32 pm
- Forum: Electronegativity
- Topic: Acidity
- Replies: 4
- Views: 435
Re: Acidity
This link has a good diagram for electronegativity and acidity. Acid strength increases with increasing electronegativity of the central atom because the OH bond is more polarized. https://groups.chem.ubc.ca/courseware/pH/section10/index.html#:~:text=Acid%20strength%20increases%20with%20%3A,for%20th...
- Sun Dec 06, 2020 11:17 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Coordination Number
- Replies: 13
- Views: 974
Re: Coordination Number
The coordination number is equal to how many atoms the central atom is bonded to. You use it to determine the name of the coordination complex
- Sun Dec 06, 2020 10:35 pm
- Forum: Student Social/Study Group
- Topic: How are you?
- Replies: 154
- Views: 15273
Re: How are you?
Just in the home stretch and excited for this quarter to be over! Can't wait to have some time to relax during break.
- Sun Nov 29, 2020 9:48 pm
- Forum: Hybridization
- Topic: Sapling #11
- Replies: 19
- Views: 919
Re: Sapling #11
Shapes like that can be really intimidating, but just remember to look at the atom the question is referring to and focus on that. I think those shapes are meant to distract, but it really is all the same rules for hybridization despite the confusing shape.
- Sun Nov 29, 2020 9:46 pm
- Forum: Hybridization
- Topic: Explaining Hybridization
- Replies: 2
- Views: 501
Re: Explaining Hybridization
The explanation above is really great! I would also just say that overall, orbitals hybridize when chemical bonds are forming so that electrons from the atoms can be paired. I usually imagine it like a venn diagram in terms of shape overlap
- Sun Nov 29, 2020 9:36 pm
- Forum: Hybridization
- Topic: End vs side
- Replies: 3
- Views: 172
End vs side
How do you know when orbitals overlap at the ends vs at the sides? They look the same in the diagram
- Sun Nov 29, 2020 9:26 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Bond angles
- Replies: 8
- Views: 343
Re: Bond angles
Hi! I think the primary tool we are supposed to use for determining bond angles are the shapes from the formulas that Lavelle has been talking about. Based on those formulas, there is a pretty definitive set for bond angles, which are still approximations but it's my those angular approximations can...
- Sun Nov 29, 2020 8:09 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: sigma vs pi bonds
- Replies: 33
- Views: 2163
Re: sigma vs pi bonds
How do you determine if the overlap is end to end vs side to side? They look basically the same in the diagrams. Thanks!
- Sun Nov 22, 2020 11:28 pm
- Forum: *Liquid Structure (Viscosity, Surface Tension, Liquid Crystals, Ionic Liquids)
- Topic: Viscosity
- Replies: 25
- Views: 3363
Re: Viscosity
A high viscosity substance has high resistance to deformation due to strong intermolecular forces. This means it resists flow, so water is low viscosity.
- Sun Nov 22, 2020 11:23 pm
- Forum: Student Social/Study Group
- Topic: Final Jitters
- Replies: 457
- Views: 382497
Re: Final Jitters
For me, it helps to look at the outlines and check off what I know and what I need to work on. Once I know that I develop the knowledge by doing the practice problems/watching videos if I must. It also helps that you can always post questions on here!
- Sun Nov 22, 2020 11:21 pm
- Forum: Lewis Acids & Bases
- Topic: Determining Lewis Acids and Bases
- Replies: 9
- Views: 609
Re: Determining Lewis Acids and Bases
You know that it is an electron acceptor if it needs to take on an electron to fill the shell. So this would be figured out by counting the valence electrons and then seeing what shell of the orbital that is and how many electrons it would have if it were full
- Sun Nov 22, 2020 11:02 pm
- Forum: Student Social/Study Group
- Topic: Studying From Home
- Replies: 91
- Views: 7500
Re: Studying From Home
It is for sure hard to study at home and I totally get you. Personally, I have struggled a lot to discipline myself and actually sit down and do stuff, especially when there isn't always a quiet place with enough room. I've found it very useful to set a timer when I'm studying or doing work and to s...
- Sun Nov 22, 2020 4:23 pm
- Forum: Student Social/Study Group
- Topic: Exercising Our Minds and Bodies
- Replies: 120
- Views: 22067
Re: Exercising Our Minds and Bodies
I go on bike rides every day which as been such a good source of exercise and entertainment for me!
- Sun Nov 15, 2020 11:54 pm
- Forum: Octet Exceptions
- Topic: octet rule
- Replies: 8
- Views: 641
Re: octet rule
can someone revisit the octet rule conceptually again? The octet rule says that atoms prefer to have eight electrons in their valence shell, and if they don't have eight, they will react with others to form stable compounds. I found this link gives a pretty good explanation https://chem.libretexts....
- Sun Nov 15, 2020 11:49 pm
- Forum: Ionic & Covalent Bonds
- Topic: bond lengths
- Replies: 9
- Views: 566
Re: bond lengths
I agree with lots of these responses, think of it like if there is more pull = more power = closer together.
- Sun Nov 15, 2020 11:46 pm
- Forum: Coordinate Covalent Bonds
- Topic: Lone Pairs and Lewis Bases
- Replies: 4
- Views: 294
Re: Lone Pairs and Lewis Bases
Yeah, lewis basis typically have lone pairs on the central atom so that they can donate to compounds that will accept electrons.
- Sun Nov 15, 2020 10:38 pm
- Forum: Student Social/Study Group
- Topic: Oxidation Numbers on Midterm
- Replies: 5
- Views: 314
Re: Oxidation Numbers on Midterm
Also on that note, since it seems like we are all quite confused about oxidation numbers, can anyone explain what the concept is? I also noticed on the sapling problems that the explanations were not very clear and it seems like a relevant concept.
- Sun Nov 15, 2020 9:38 pm
- Forum: Coordinate Covalent Bonds
- Topic: Hydrogen bonds
- Replies: 20
- Views: 1376
Re: Hydrogen bonds
Their electronegativities are too similar. Because hydrogen bonds are formed from electron via a difference in electronegativity, it won't happen when a hydrogen and a carbon are near each other that level of pulling does not occur.
- Sun Nov 08, 2020 11:11 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm 1 answer key
- Replies: 13
- Views: 760
Re: Midterm 1 answer key
My TA told us that if we want to go over the problems we can do it in office hours, they just can't post the test material. So if you want to know why you got stuff wrong before the midterm (even though it is not cumulative) I would go to office hours!
- Sun Nov 08, 2020 11:09 pm
- Forum: Ionic & Covalent Bonds
- Topic: London dispersion forces
- Replies: 12
- Views: 820
Re: London dispersion forces
I believe most replies above have the definition of London dispersion forces. Here is the order of bond strengths from strongest to weakest 1. Ionic bonds 2. Covalent bonds 3. Dipole Dipole bonds 4. Van der Waals (London dispersion) Are London Disperson/Van der Waals considered a form of bond? Or a...
- Sun Nov 08, 2020 10:51 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Midterm 2 [ENDORSED]
- Replies: 11
- Views: 729
Re: Midterm 2 [ENDORSED]
305614361 wrote:When are we taking the second midterm?
The second midterm is during week 7 discussion
- Sun Nov 08, 2020 10:46 pm
- Forum: Student Social/Study Group
- Topic: Mid-quarter Check in
- Replies: 67
- Views: 3883
Re: Mid-quarter Check in
This is such a nice thread. I didn't realize how hard it would be not to be able to collaborate in person for classes like this. It really affects my entire understanding of the material and I think I took that for granted. But I really appreciate all the effort that has been made by the instructors...
- Sun Nov 08, 2020 10:42 pm
- Forum: Student Social/Study Group
- Topic: Midterm 2
- Replies: 28
- Views: 1182
Re: Midterm 2
Can someone elaborate on the step-up sessions, I'm kind of confused about what happens in them. Are they worthwhile? Thanks
- Sun Nov 01, 2020 11:42 pm
- Forum: DeBroglie Equation
- Topic: When to use de Broglie and what numbers to use
- Replies: 8
- Views: 495
Re: When to use de Broglie and what numbers to use
Is there a definite answer for when to use de Broglie and when not to? I thought that it was straightforward but then it seemed like it was being applied to whatever they wanted it to be applied to in the sapling problems. Like you are able to calculate using de broglie for electrons but then also n...
- Sun Nov 01, 2020 11:32 pm
- Forum: General Science Questions
- Topic: Sapling #24
- Replies: 1
- Views: 159
Re: Sapling #24
Hi! Based on my understanding, the "2p electrons in fluorine are experiencing a higher effective nuclear charge than those in oxygen" is the opposite of the answer about shielding. So if the electrons in fluorine were more highly shielded, that would mean that they would experience a lower...
- Sun Nov 01, 2020 11:26 pm
- Forum: Ionic & Covalent Bonds
- Topic: Sampling 28
- Replies: 10
- Views: 301
Re: Sampling 28
There will be multiple l values for an n value unless the letter of the orbital is specified, unless it's n=1 because there is only one subshell. FOr example if all you're given is that n=2, l could be 0 or 1 depending on the subshell letter. Hope that helps!
- Sun Nov 01, 2020 10:38 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: Good way to understand quantum numbers/shells?
- Replies: 3
- Views: 725
Good way to understand quantum numbers/shells?
Hi! I remember having a good understanding of orbital shells and quantum numbers in high school but I cannot seem to get the same grip on it that I used to have. Does anyone have any tips or good videos for understanding it and being able to apply it to problems? Thanks
- Sun Nov 01, 2020 9:27 pm
- Forum: DeBroglie Equation
- Topic: average wavelength
- Replies: 3
- Views: 257
Re: average wavelength
Hey Monica! So for that one you'd have to use DeBroglie's wavelength. (Wavelength=planck's constant/mass x velocity) You're already given the velocity so now you'd just find the mass of a Chlorine atom. In this case, since they said it's a diatomic molecule so you'd multiple 2(the molar mass of chl...
- Sun Oct 25, 2020 7:36 pm
- Forum: *Black Body Radiation
- Topic: What is Black Body?
- Replies: 53
- Views: 2469
Re: What is Black Body?
He said in the lecture that we do not need to know about black body radiation for this class, but if it's just a curiosity thing I found this link pretty explanatory
http://galileo.phys.virginia.edu/classe ... ation.html
http://galileo.phys.virginia.edu/classe ... ation.html
- Sun Oct 25, 2020 7:31 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: for test 1
- Replies: 14
- Views: 952
Re: for test 1
Definitely just an application thing, but i don't think there would be a question where you'd have to differentiate between definitions or anything like that.
- Sun Oct 25, 2020 7:27 pm
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: for test 1
- Replies: 14
- Views: 952
Re: for test 1
Definitely just an application thing, but i don't think there would be a question where you'd have to differentiate between definitions or anything like that.
- Sun Oct 25, 2020 7:22 pm
- Forum: Administrative Questions and Class Announcements
- Topic: midterm 1
- Replies: 10
- Views: 444
Re: midterm 1
I do not think there will be very many since it's only a 50 minute period, but on a related note, does anyone know the format?
- Sun Oct 25, 2020 7:14 pm
- Forum: Student Social/Study Group
- Topic: How to relax
- Replies: 168
- Views: 28911
Re: How to relax
I love riding my bike around Westwood and other parts of LA! it's so nice to get fresh air and fun to do with friends.
- Sun Oct 25, 2020 7:07 pm
- Forum: SI Units, Unit Conversions
- Topic: Can someone explain Avogrado's #?
- Replies: 8
- Views: 969
Re: Can someone explain Avogrado's #?
Avogadro's number is just the number of "something" (units) in a mole. A "dozen" is 12 of "something" -- that could be 12 pounds, 12 kilograms, 12 grams etc. Think of the mole in the same way regarding avogadro's number. A mole is [avogadro's number] of an object.
- Sun Oct 18, 2020 11:39 pm
- Forum: Properties of Light
- Topic: Photon vs Quantum
- Replies: 7
- Views: 261
Re: Photon vs Quantum
Relating to this, I am struggling to understand conceptually how this all relates to the bigger picture. The last time I took chemistry was tenth grade and while we did go in-depth, it included no discussion of photons. So in terms of quantum, are we just using photons as our prime example regarding...
- Sun Oct 18, 2020 11:27 pm
- Forum: Properties of Electrons
- Topic: Light Emission
- Replies: 4
- Views: 631
Re: Light Emission
Based on what I know, there is a correlation between photon energy level and color of light emitted. The energy level of the photon absorbed by the element can excite the atom's electron and make it jump and then fall back down. So based on my understanding the number of energy levels it falls will ...
- Sun Oct 18, 2020 11:21 pm
- Forum: Properties of Electrons
- Topic: Energy of photons vs electrons
- Replies: 2
- Views: 204
Re: Energy of photons vs electrons
I get what you are asking and I am also confused by it. I found what seems to be some pretty in-depth explanations at this link https://physics.stackexchange.com/questions/110844/why-electrons-have-less-energy-than-photons-with-the-same-wavelength But I am having a hard time understanding it, based ...
- Sun Oct 18, 2020 11:16 pm
- Forum: Trends in The Periodic Table
- Topic: Period Trends
- Replies: 11
- Views: 555
Re: Period Trends
Atomic radius increases as group level increases and atomic radius decreases as you move across a period
- Sun Oct 18, 2020 10:39 pm
- Forum: Student Social/Study Group
- Topic: How are you studying?
- Replies: 204
- Views: 21926
Re: How are you studying?
Are the practice problems that people are using in the book or from elsewhere? Typically I do the discussion section problems and the sapling hw but I'm not sure where else I should go for more problems because I feel like I am not that good at the application.
- Sun Oct 11, 2020 11:56 pm
- Forum: Molarity, Solutions, Dilutions
- Topic: Molarity and Dilution of a Solution
- Replies: 7
- Views: 389
Re: Molarity and Dilution of a Solution
Moles will stay the same as long as you do not add more solute. However, say you're adding more water, which will increase the volume, that would decrease the molarity because adding more solvent decreases the concentration. So despite there being the same number of moles, the molarity is less.
- Sun Oct 11, 2020 11:52 pm
- Forum: Empirical & Molecular Formulas
- Topic: Trouble with Sapling Question #8
- Replies: 4
- Views: 353
Re: Trouble with Sapling Question #8
^ Yes try capitals, that's what worked for me
- Sun Oct 11, 2020 11:51 pm
- Forum: Student Social/Study Group
- Topic: Regarding Quizzes
- Replies: 5
- Views: 166
Re: Regarding Quizzes
I was not told about any quizzes or respondus but if it's written in print anywhere I'd love to see!