Search found 100 matches
- Sun Mar 14, 2021 3:58 am
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 4E #7b
- Replies: 3
- Views: 375
Re: 4E #7b
Hi! For these kinds of problems, we can do ∑H˚m(bonds broken) - ∑H˚m(bonds formed). Like Lea said, I usually just break up all the bonds and add them together, so that I’m essentially just doing [reactant bonds] - [product bonds]. Hope this helps!
- Sun Mar 14, 2021 3:52 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Adding Pt(s)
- Replies: 5
- Views: 384
Re: Adding Pt(s)
Hi! I agree with what Brennan said. We want our galvanic cells to have some solid electrode on both sides, so in the absence of a solid electrode, we often add in Pt(s) or some other conducting solid. An exception to this is liquid mercury, which can serve as an electrode. Hope this helps!
- Sun Mar 14, 2021 3:38 am
- Forum: General Rate Laws
- Topic: Rate laws and reactions
- Replies: 4
- Views: 442
Re: Rate laws and reactions
Hi! Like others have stated above, I believe that we will be told which elementary steps are slow or fast. As far as comparing the speed of reactions with each other goes, we can examine the rate laws. Hope this helps!
- Sat Mar 13, 2021 2:00 am
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Textbook 7.9
- Replies: 2
- Views: 206
Re: Textbook 7.9
Hi! I agree with what Emily wrote above. For this problem, I considered the rate laws for the two different mechanisms. (i) would likely be rate = k[C12H22O11], as the slow rate of step 1 limits the overall rate. (ii) would likely be rate = k[C12H22O11][H2O]. Typically, we would expect H2O to be exc...
- Sat Mar 13, 2021 1:39 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Textbook 7E.3
- Replies: 3
- Views: 294
Re: Textbook 7E.3
Hi! Like others mentioned above, for part A, I used the Arrhenius equation k = Ae^(-Ea/RT). Because we are comparing the two different pathways (one without the catalyst and one with the catalyst), we can compare k1 and k2, where k1 is the reaction rate for the catalyst pathway and k2 is the reactio...
- Sun Mar 07, 2021 9:20 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Notation
- Replies: 5
- Views: 429
Re: Cell Notation
Hi! I’m still a little confused by cell notation myself, but I believe that this specific order tends to take place because we write the species in the order that electrons move between them / the order they are in contact. For example, Sapling gives this solution for one of the homework problems: P...
- Sun Mar 07, 2021 8:58 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook 6L.2
- Replies: 3
- Views: 231
Re: Textbook 6L.2
Hi! I agree with Jayasree. Because HCl is a strong acid, it dissociates into H+ and Cl-. So this would only occur for compounds that completely dissociate, not all aqueous solutions. Hope this helps!
- Sun Mar 07, 2021 8:52 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Texbook 6M.5
- Replies: 2
- Views: 254
Re: Texbook 6M.5
Hi! I used Appendix 2B in the textbook for these problems; these are the same ones used in 6L. Hope this helps!
- Sun Mar 07, 2021 8:50 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook 6L.9
- Replies: 2
- Views: 286
Re: Textbook 6L.9
Hi! I’m also not sure if this is the fastest way, but I also started by identifying Mn and Fe as the species most likely involved in the redox reaction. I then looked up the cell potentials in Appendix 2B, balanced the half-reactions. +1.23 V corresponds to Mn and +0.77 V to Fe, so subtracting E˚(ca...
- Sat Mar 06, 2021 10:39 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Textbook 6L.5B Cell Diagram
- Replies: 1
- Views: 131
Textbook 6L.5B Cell Diagram
For 6L.5B in the textbook, the solution manual gives shorthand notation: Pt(s)|I-(aq)|I2(s)||Ce4+(aq),Ce3+(aq)|Pt(s). I thought that we were supposed to write aqueous species closest to the double lines (salt bridge). Is that correct? And if so, why is solid I2 closer to the double lines than aqueou...
- Sun Feb 28, 2021 11:47 pm
- Forum: Balancing Redox Reactions
- Topic: Sapling 1
- Replies: 5
- Views: 381
Re: Sapling 1
Hi Ryan! Like others mentioned above, we can look at the polyatomic ion ClO3-, which has a charge of -1. If O is -2, Cl must be +5 to allow the ion to reach a charge of -1. Hope this helps!
- Sun Feb 28, 2021 11:43 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Sapling Week 7/8 #15
- Replies: 11
- Views: 699
Re: Sapling Week 7/8 #15
Hi! Like Ryan explained above, we can use the Nernst equation E = E˚- (RT/nF)*ln(Q) for this problem. Finding E˚: We can find the E˚ of the cell by doing E˚(cathode) - E˚(anode). Based on the fact that Zn is being oxidized, we know it is the anode and Sn is the cathode. Finding Q: We have the molar ...
- Sun Feb 28, 2021 11:36 pm
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: sampling week 8 & 9 assignment #5
- Replies: 2
- Views: 166
Re: sampling week 8 & 9 assignment #5
Hi! For this problem, I referred to Toolbox 6K.1 and just went through the steps to balance the equations. Here are the steps, in short. 1- Identify what is being oxidized and what is being reduced. 2- Write the two unbalanced oxidation and reduction half-reactions. 3- Balance all the non-hydrogen o...
- Sun Feb 28, 2021 11:30 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Sapling Week 7/8 #12
- Replies: 5
- Views: 418
Re: Sapling Week 7/8 #12
Hi! For this problem, you are correct to use ∆G=-nFE˚. You can use the standard reduction potentials you found in E˚(cathode) - E˚(anode) to get E˚(cell). Then, consider how many electrons are being transferred to get n. After plugging in these values to ∆G˚=-nFE˚, you should get your answer in joul...
- Sun Feb 28, 2021 11:26 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Sapling Week 7/8 #7 ion movement
- Replies: 6
- Views: 325
Re: Sapling Week 7/8 #7 ion movement
Hi! As mentioned above, potassium is not included in either of the half reactions because it is solely responsible for keeping the solution neutral; potassium would not react in the redox reaction. Hope this helps!
- Sun Feb 21, 2021 5:03 pm
- Forum: Balancing Redox Reactions
- Topic: Cathode v Anode
- Replies: 8
- Views: 473
Re: Cathode v Anode
Hi! Like others have mentioned above, I believe that the anode corresponds to the side losing electrons (oxidation) and the cathode corresponds to the side gaining electrons (reduction). So we can consider which direction the electrons are moving to figure it out. Hope this helps!
- Sun Feb 21, 2021 4:59 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Spontaneous Reduction
- Replies: 9
- Views: 561
Re: Spontaneous Reduction
Hi! Like others have mentioned above, I believe that we are supposed to consider the sign of the standard electrode potential for the reaction. A positive value would be spontaneous; a negative value would not be spontaneous. You can also think of this in terms of ∆G˚, as a positive E˚ would yield a...
- Sun Feb 21, 2021 4:54 pm
- Forum: Balancing Redox Reactions
- Topic: Salt Bridge Diagram
- Replies: 8
- Views: 475
Re: Salt Bridge Diagram
Hi! Like others have mentioned above, I think that we can just assume that the anode is on the left and the cathode on the right for cell diagrams in this class, although this is likely just an arbitrary choice to set up the model.
- Sun Feb 21, 2021 4:51 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 5
- Views: 308
Re: Salt Bridge
Hi! Like others have mentioned above, a salt bridge helps maintain the neutrality of each system. The salt bridge essentially transfers electrons to counteract the buildup of positive and negative charges, which would eventually lead to a charge imbalance that would “halt” the reaction. Hope this he...
- Sun Feb 21, 2021 4:48 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Salt Bridge
- Replies: 6
- Views: 378
Re: Salt Bridge
Hi! Like others have explained above, a salt bridge serves to keep the systems neutral by transferring electrons to prevent positive and negative charges from building up and “halting” the electrode reaction as a result of an imbalance in charge. Hope this helps!
- Sun Feb 14, 2021 12:29 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: week 5 and 6 sampling hw #7
- Replies: 5
- Views: 355
Re: week 5 and 6 sampling hw #7
Hi! Like others have mentioned above, we can calculate the mass difference to determine the amount of substance that has vaporized. After dtermining the mols of vaporized substance, we can divide the energy supplied by the heater by this value, giving us our ∆Hvap. Hope this helps!
- Sun Feb 14, 2021 12:26 pm
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Sapling Week 6 Question 1
- Replies: 6
- Views: 373
Re: Sapling Week 6 Question 1
Hi! Like others have mentioned above, N2O has residual entropy because it is not symmetrical, and thus can be rearranged into other unique positions. Based on formal charge, we know that N2O tends to be arranged as N≡N-O, but we could also write O-N≡N. Because there are possible variations in N2O’s ...
- Sun Feb 14, 2021 12:16 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Sapling #10 WK5/6
- Replies: 3
- Views: 2289
Re: Sapling #10 WK5/6
Hi! Like others have mentioned above, we can start by looking at ∆G. Because this reaction is spontaneous, ∆G must be negative. Because the water molecules are moving from a more mobile form (gaseous) to being bound to the solid silica gel, ∆S must be negative. We can then apply this to the Gibbs eq...
- Sun Feb 14, 2021 12:08 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling #7 Weeks 5/6
- Replies: 3
- Views: 175
Re: Sapling #7 Weeks 5/6
Hi! Like Peter mentioned above, I started by determining the amount of energy was made available by the heater in the given 6.31 minutes. We know that the heater supplies 475.0 W, or 475.0 J/s. From there, we can do (6.31 min)(60 s/min)(475.0J/s)(1 kJ/1000 J)--putting this value in units of kJ is he...
- Sun Feb 14, 2021 11:55 am
- Forum: Concepts & Calculations Using Second Law of Thermodynamics
- Topic: Sapling #1wk5/6
- Replies: 4
- Views: 212
Re: Sapling #1wk5/6
Hi! Like Sophia explained above, determining whether compounds have residual entropies involves considering how many possible unique positions there are in their crystalline forms. If there is only one possible position, then we would not expect to find residual entropy. For example, CO2 is symmetri...
- Sun Feb 07, 2021 10:44 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Sapling Week 3/4 #10
- Replies: 4
- Views: 158
Re: Sapling Week 3/4 #10
Hi! Like others have explained above, we need to find: 1. q(ice), 2. q(water), 3. deltaH. We can find q(ice) and q(water) by using m*C*(Tf-Ti). After plugging in values, we should have q(ice) and q(water) in terms of Tf. To find deltaH, we can take the number of grams of the ice cube, convert it to ...
- Sun Feb 07, 2021 10:40 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling 3/4 #10
- Replies: 5
- Views: 183
Re: Sapling 3/4 #10
Hi! Like others have explained above, we can set q(ice) + deltaHfusion = - qwater, and then solve for Tf. This honestly took me a couple tries to not mess up the numbers in my calculator haha but it should work out!
- Sun Feb 07, 2021 10:35 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling 3/4 #12 part b
- Replies: 3
- Views: 138
Re: Sapling 3/4 #12 part b
Hi! Yes, we would use the same constant C found in part A, since this describes the heat capacity of the calorimeter (calorimeter constant), and we are using the same calorimeter for part B. Hope this helps!
- Sun Feb 07, 2021 10:33 pm
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Sapling 10 week 4
- Replies: 3
- Views: 156
Re: Sapling 10 week 4
Hi! Based on your work, I think you lost your Tf term on the ice cube side of the question. When you did
(46.8/18.02)(6.01x10^3) + (46.8 x 4.18)(Tf - 0) = 1.58x10^4,
the Tf term seems to disappear. Instead, it should be 1.58x10^-4 * Tf. Hope this helps!
(46.8/18.02)(6.01x10^3) + (46.8 x 4.18)(Tf - 0) = 1.58x10^4,
the Tf term seems to disappear. Instead, it should be 1.58x10^-4 * Tf. Hope this helps!
- Sun Feb 07, 2021 10:26 pm
- Forum: Thermodynamic Systems (Open, Closed, Isolated)
- Topic: Molar Heat Capacities at Constant Volume/Pressure
- Replies: 3
- Views: 120
Re: Molar Heat Capacities at Constant Volume/Pressure
Hi! Like Allyssa and Aydin stated already, I also believe that we will be given the values for specific and molar heat capacities in the problem! It might be helpful to be familiar with the specific heat of liquid water, though, since it does come up quite frequently.
- Sun Jan 31, 2021 8:27 pm
- Forum: Phase Changes & Related Calculations
- Topic: Sapling Week 3 & 4: Question 8
- Replies: 4
- Views: 237
Re: Sapling Week 3 & 4: Question 8
Hi! For the second part of this question, we can take the 169 g of carbon and convert to mols using the molar mass. From there, we can do the stoichiometry to determine the amount of energy released, given that there are 358.8 kJ per 4 mols of carbon (based on the equation). For the third part, we c...
- Sun Jan 31, 2021 8:22 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: 4D.15
- Replies: 4
- Views: 267
Re: 4D.15
Hi! Like Rita stated above, a combustion reaction simply describes a reactant reacting with oxygen gas (O2). Typically, this can be simplified to [reactant] + O2 —> CO2 + H2O. However, there are some exceptions to this general rule of thumb; for example, the combustion of hydrogen gas (H2) produces ...
- Thu Jan 28, 2021 5:55 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Sapling #8 Weeks 3&4
- Replies: 10
- Views: 531
Re: Sapling #8 Weeks 3&4
Hi! For this part of the problem, consider that the delta H can be considered “stoichiometrically”; that is, it is proportional to the molar coefficient laid out in the reaction. As such, we can say that there is +358.8 kJ / 1 mol S8(s). From there, the problem tells us that 1.31 mol S8 is reacting,...
- Thu Jan 28, 2021 5:15 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Reaction Enthalpies
- Replies: 3
- Views: 239
Re: Reaction Enthalpies
Hi! For this problem, we can consider the equation deltaH rxn = [sum of enthalpy of formation (products)] - [sum of enthalpy of formation (reactants)]. If we were to use enthalpy of formation, deltaH rxn would equal [enthalpy of formation of CH4(g)] - [enthalpy of formation of C(g) + 4 * enthalpy of...
- Thu Jan 28, 2021 5:06 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Textbook Problem 4D.15
- Replies: 3
- Views: 249
Re: Textbook Problem 4D.15
Hi! As others have specified above, the given values are standard enthalpies of combustion. Thus, we can write out the combustion reactions, where each molecule/compound essentially reacts with oxygen gas to form H2O and/or CO2, using the enthalpies of combustion as reaction enthalpies per mol of th...
- Sun Jan 24, 2021 10:02 pm
- Forum: Calculating the pH of Salt Solutions
- Topic: Textbook problem 6B.3 part b
- Replies: 3
- Views: 361
Re: Textbook problem 6B.3 part b
Hi! Like Joyce said above, I would also use the dilution equation M1V1 = M2V2 to find the actual concentration, getting (0.025)(200.0) = [HCl](250.0), where [HCl] = 0.020 mol/L. Because there is a 1:1 ratio between HCl and H3O+, [HCl] = [H3O+] = 0.020 mol/L. Then, we can use pH = -log[H3O+]. Hope th...
- Sun Jan 24, 2021 9:57 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Textbook Q 5I.13
- Replies: 4
- Views: 191
Re: Textbook Q 5I.13
HI! For part C, I simply considered how “likely” Cl2 and F2 were to break into their monatomic forms relative to each other. Because the molar concentration of Cl in part a was 1.1 x 10^-5 mol/L and the molar concentration of F in part b was 3.2 x 10^-4 mol/L, [Cl] < [F], despite the two both starti...
- Sun Jan 24, 2021 9:49 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Textbook Question 6B.5
- Replies: 3
- Views: 226
Re: Textbook Question 6B.5
Hi! For these problems, I usually start off by writing out the equations, and then figure out where to go from there. It’s important to note that all the solutions in this question are strong acids/bases, so they will go to completion. The main objective is to determine [H3O+] or [OH-], and from the...
- Sun Jan 24, 2021 9:37 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: 6A.23 Textbook Question
- Replies: 4
- Views: 251
Re: 6A.23 Textbook Question
Hi! For this problem, it’s helpful to know that because Ba(OH)2 is an alkaline earth hydroxide, it is a strong base. As such, we would expect the reaction Ba(OH)2(aq) —> Ba2+(aq) + 2OH-(aq) to go to completion. To start, we can convert the 0.43g Ba(OH)2 to its molar concentration (use molar mass and...
- Sun Jan 24, 2021 9:26 pm
- Forum: Calculating pH or pOH for Strong & Weak Acids & Bases
- Topic: Textbook problem 6D.15
- Replies: 3
- Views: 550
Re: Textbook problem 6D.15
Hi! I also had some trouble finding the Ka value in the textbook at first, but it is available in Table 6D.1 (page 477). I approached this problem by writing out the equation Al(H2O)3+(aq) + H2O(l) <—> H3O+(aq) + Al(H2O)2(OH-)2+(aq) , where Al3+ is a small, highly-charged metal cation that can act a...
- Sun Jan 17, 2021 11:36 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling WK 1, #4
- Replies: 3
- Views: 532
Re: Sapling WK 1, #4
Hi! Like others have stated above, we want to start with an ICE table.
(I) The initial pressures of PCl3 and Cl2 will be 0, as the container only consists of PCl5. The initial pressure of PCl5 is given as 0.0750 bar.
(C) Because the system will favor the reverse reaction to reach equilibrium, PCl5...
- Sun Jan 17, 2021 11:25 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Autoprotolysis Constant of Water
- Replies: 7
- Views: 291
Re: Autoprotolysis Constant of Water
Hi! I agree that this concept is likely an important one to remember, as it serves as the foundation for understanding pH, pOH, acids, bases, etc., as well as the relationships between all these concepts. I would definitely try to remember it for both problem solving and conceptual questions. Hope t...
- Sun Jan 17, 2021 11:21 am
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Endothermic/exothermic reactions and K
- Replies: 11
- Views: 576
Re: Endothermic/exothermic reactions and K
Hi! For exothermic reactions, heat is released for the forward reaction; thus, the addition of heat would favor the reverse reaction instead to produce more reactants, and the K value would decrease. For endothermic reactions, heat is absorbed for the forward reaction; thus, the addition of heat wou...
- Sun Jan 17, 2021 11:15 am
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Sapling #10, WK 1
- Replies: 8
- Views: 376
Re: Sapling #10, WK 1
Hi! For the final part of this question, we can set up an ICE box.
(I) The initial concentration of N2O4 is unchanged, so we can leave it at 0.373 mol/L; the initial concentration of NO2 needs to account for the additional 1.00 mol added, so that would be 2.04 + 1.00 mol/L.
(C) Because the product...
- Sun Jan 17, 2021 11:04 am
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: Autoprotolysis Reaction and Kw
- Replies: 3
- Views: 94
Re: Autoprotolysis Reaction and Kw
Hi! Like others have pointed out above, Kw changes with temperature. Because the reaction is endothermic, the forward reaction will absorb heat; an increase in temperature will thus favor the formation of products more, and the equilibrium constant will increase.
- Sun Jan 10, 2021 6:45 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Equilibrium mixture
- Replies: 4
- Views: 123
Re: Equilibrium mixture
Hi! Like others have explained above, I believe that the two terms can be used interchangeably; however, the mixture is usually used to describe the whole reaction/system, whereas the concentration is slightly more specific in describing a particular product or reactant.
- Sun Jan 10, 2021 6:42 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: How does an inert gas effect a closed system with these certain conditions?
- Replies: 5
- Views: 341
Re: How does an inert gas effect a closed system with these certain conditions?
Hi! Like others have said above, the addition of an inert gas to a closed container would likely result in an increase in pressure, but the volume would remain unchanged.
- Sun Jan 10, 2021 6:38 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Changes in Q vs K
- Replies: 6
- Views: 546
Re: Changes in Q vs K
Hi! Like others have explained above, K does not change in response to changes in pressure because the reaction will simply shift to minimize any change in concentration (as specified in Le Chatelier’s principle). However, in the case of temperature, the reaction will change in the way it favors pro...
- Sun Jan 10, 2021 6:34 pm
- Forum: Non-Equilibrium Conditions & The Reaction Quotient
- Topic: Stable Reactants and Products
- Replies: 7
- Views: 247
Re: Stable Reactants and Products
Hi! Like others have detailed above, stability can point to whether the reaction will favor forming a reactant or a product. When the equilibrium constant is large, there is a greater proportion of products, suggesting that the products are more stable and the reaction favors the forward direction. ...
- Sun Jan 10, 2021 6:19 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: K=1
- Replies: 8
- Views: 386
Re: K=1
Hi! Like others have mentioned above, when the equilibrium constant is 1, the concentration/pressure of the products and reactants will be equal. To my understanding, this just happens to be rare because there is usually a tendency for reactions to favor one direction over another.
- Tue Dec 15, 2020 12:01 pm
- Forum: Conjugate Acids & Bases
- Topic: Oxyacids
- Replies: 8
- Views: 601
Re: Oxyacids
Hi! Like others have said above, an oxyacid is an acid that contains oxygen, hydrogen, and another element. At least one acidic hydrogen is bonded to an oxygen atom. The more oxygen atoms (or the higher the oxidation number), the stronger the acid.
- Tue Dec 15, 2020 11:56 am
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Ligands
- Replies: 8
- Views: 465
Re: Ligands
Hi! Like others have said above, coordination compounds can definitely have multiple types of ligands, which we list alphabetically in naming.
- Sat Dec 12, 2020 4:30 pm
- Forum: Bronsted Acids & Bases
- Topic: Textbook Problem J.9 part b
- Replies: 3
- Views: 321
Re: Textbook Problem J.9 part b
A weak acid will still donate protons. It does not dissociate completely, so there will be some H3PO4 left at equilibrium, but there will also be some of the salt present. if weak acids/bases didn't dissociate at all, they wouldn't be able to participate in an A/B reaction. Hi Zach, I also had this...
- Sat Dec 12, 2020 4:22 pm
- Forum: Bronsted Acids & Bases
- Topic: SO3 lewis acid/bronsted
- Replies: 2
- Views: 1871
Re: SO3 lewis acid/bronsted
Hi! To my understanding, SO3 is not a Bronsted acid or base, as it cannot donate or accept a proton. You are right that it is a Lewis acid in water because the sulfur accepts an electron pair, but this electron pair should come from the oxygen atom, not H+ (depicted in the attached image). Perhaps y...
- Sat Dec 12, 2020 1:08 am
- Forum: Bronsted Acids & Bases
- Topic: Fundamentals J #9b
- Replies: 2
- Views: 208
Fundamentals J #9b
For Fundamentals #9b, I was wondering why the weak acid reactant H3PO4 in the neutralization reaction is written in its dissociated form [3H+(aq) + PO4 3-(aq)], as I thought that only strong acids were supposed to be written out as such. For example, the bromous acid (also a weak acid) in part c is ...
- Sun Dec 06, 2020 9:18 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Sapling 5
- Replies: 6
- Views: 408
Re: Sapling 5
Hi! Like others have explained above, (en) is the ethylenediamine ligand, or NH2CH2CH2NH2 (you can find this in Table 9C.1), which is a bidentate ligand. To calculate the coordination number, we would consider the number of bonds that the metal (Co) can form with the ligands (en and CO). There are t...
- Sun Dec 06, 2020 9:11 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Homework Problem 9C.5
- Replies: 3
- Views: 237
Re: Homework Problem 9C.5
Hi! When I did this problem, I drew out the Lewis structures for each ligand, and then determined the number of lone pairs on different atoms. For example, the Lewis structure for (a) HN(CH2CH2NH2)2 reveals three nitrogen atoms with one lone pair each. Because there are three separate lone pairs tha...
- Sun Dec 06, 2020 8:58 pm
- Forum: Naming
- Topic: Textbook Exercise 9C.3
- Replies: 4
- Views: 261
Re: Textbook Exercise 9C.3
Hi! Like others have said above, the potassium should be located at the beginning, in front of the brackets, because it is a cation (more specifically, a positively-charged metal) with a 1+ charge. Potassium hexacyanidochromate (III) is a compound, so we name the cation first and then the anion.
- Sun Dec 06, 2020 7:23 pm
- Forum: Shape, Structure, Coordination Number, Ligands
- Topic: Figuring Out monodentate, bidentate, etc
- Replies: 5
- Views: 272
Re: Figuring Out monodentate, bidentate, etc
Hi! To my understanding, a monodentate ligand describes a ligand that binds at one site of a central metal atom, donating one electron pair. A bidentate would be a ligand that binds at two sites, donating two electron pairs, and so on. To determine what kind of dentate a ligand is, we can consider t...
- Sun Dec 06, 2020 7:18 pm
- Forum: Naming
- Topic: Sapling Week 9 #1
- Replies: 6
- Views: 361
Re: Sapling Week 9 #1
Hi! Like others mentioned, Toolbox 9C.1 in the textbook and Table 9C.1 are pretty helpful for this question. But this is how I approached the problem: We would start with the part inside the brackets, [Co(NH3)5Cl]. There are three separate components: Co, NH3, and Cl. We know that Co is the transiti...
- Sun Nov 29, 2020 6:20 pm
- Forum: Hybridization
- Topic: Sapling #11
- Replies: 19
- Views: 911
Re: Sapling #11
Hi! Like others have explained above, quickly determining the hybridization primarily consists of counting the number of regions of electron density. Even in a complex structure like the one above, this holds true; we can see that each phosphorous has one lone pair and three bonds. This adds up to p...
- Sun Nov 29, 2020 6:15 pm
- Forum: Hybridization
- Topic: Sapling #18
- Replies: 10
- Views: 472
Re: Sapling #18
Hi! For all atoms to exist on the same plane, we would be essentially be able to connect them all on a 2-D plane (ex: they all could lie on the same sheet of paper). To answer the Sapling problem, we would need to consider whether there are an even or odd number of atoms. When there is an even numbe...
- Sun Nov 29, 2020 6:08 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sapling Week 7/8 HW #12
- Replies: 8
- Views: 662
Re: Sapling Week 7/8 HW #12
Hi! Like others have explained above, I started by determining the formula of the molecule. I multiplied the mass percentages with the molar mass to determine the number of moles of each element, yielding a formula of CH4O. From here, I drew the structure, keeping in mind that carbon is the most ele...
- Sun Nov 29, 2020 6:03 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sapling #20
- Replies: 5
- Views: 372
Re: Sapling #20
Hi! Like Olivia mentioned above, I would also examine the charge of the molecule or ion. In this question, we want the formal charges of the atom to have a sum of -3, as the ion has a charge of -3. Thus, the structure that would give an overall formal charge of -3 would be if arsenic had one double ...
- Sun Nov 29, 2020 5:58 pm
- Forum: Hybridization
- Topic: hybridization of phosphorus (Sapling Q.11)
- Replies: 21
- Views: 3461
Re: hybridization of phosphorus (Sapling Q.11)
Hi! This is another part of Sapling Q.11. I understood how your answers applied to the other diagram, but this diagram threw me for a loop. If any of you have advice on how to better understand and complete these questions it would be much appreciated! Thank you! Hi! Like others have detailed above...
- Sun Nov 22, 2020 5:05 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sapling Week 7 & 8 HW Question 6
- Replies: 6
- Views: 369
Re: Sapling Week 7 & 8 HW Question 6
Hi! Like others have said above, I believe the molecule you are missing is XeF2, which has Xe in the middle and F on either side of Xe, and the lone pairs are distributed fairly evenly.
- Sun Nov 22, 2020 5:02 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Polar bonds
- Replies: 8
- Views: 225
Re: Polar bonds
Hi, going off of this, I understand how to determine the polarity of a molecule but I am a little confused how to determine if an individual bond is polar or non-polar. Is it simply a large difference in electronegativity between the two atoms? Hi! I agree with the response above. To my understandi...
- Sun Nov 22, 2020 4:57 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Memorizing Shape Names
- Replies: 12
- Views: 616
Re: Memorizing Shape Names
Hi! Personally, I don’t have any specific mnemonics to remember the names of the different shapes (other than looking at the prefixes), but I usually memorize them simply by drawing them all out on a blank sheet of paper without my notes. Hope this helps!
- Sun Nov 22, 2020 4:51 pm
- Forum: Hybridization
- Topic: Pi and Sigma Bonds
- Replies: 10
- Views: 447
Re: Pi and Sigma Bonds
Hi! Like others have said above, I believe you are correct. Sigma bonds and pi bonds are found in covalent bonds, with single bonds having only a sigma bond. For double bonds and beyond, both sigma and pi bonds are present.
- Sun Nov 22, 2020 4:47 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: shape
- Replies: 6
- Views: 331
Re: shape
Hi! Like others have mentioned, I would start by drawing the Lewis structure, and then look at the bonding/lone electron pairs, which should correspond to a specific molecular shape, specified by the VSEPR model/formulas. Hope this helps!
- Sun Nov 15, 2020 8:57 pm
- Forum: Bond Lengths & Energies
- Topic: Hydrogen Bonds
- Replies: 17
- Views: 895
Re: Hydrogen Bonds
So to clarify, in conclusion, a hydrogen bond only exist between H and an N, O, or F molecule? H bonds are polar correct? Because the H is attracted to a more electronegative atom? Hi! I believe that hydrogen bonds exist between a hydrogen atom (covalently bonded specifically to F/O/N within the mo...
- Sun Nov 15, 2020 8:48 pm
- Forum: Dipole Moments
- Topic: Hydrogen Bonding
- Replies: 3
- Views: 82
Re: Hydrogen Bonding
Hi! In the case of hydrogen bonding, electrons are not considered to be shared, as hydrogen “bonding” refers to an intermolecular force. Rather, there is a force of attraction between the partial positive hydrogen and the partial negative charge of another highly electronegative atom in a separate m...
- Sun Nov 15, 2020 7:03 pm
- Forum: Resonance Structures
- Topic: Formal Charge vs. Oxidation number vs. Bond Length
- Replies: 3
- Views: 169
Re: Formal Charge vs. Oxidation number vs. Bond Length
Hi Linette! I’m not too sure, but I believe that we can use oxidation states to evaluate which Lewis structures are consistent with general oxidation state rules (oxygen usually has an oxidation state of -2 in compounds, monatomic ions have oxidation states equal to their ionic charges, etc.). If th...
- Sun Nov 15, 2020 6:50 pm
- Forum: Lewis Structures
- Topic: Sapling weeks 5/6 Question 4
- Replies: 6
- Views: 376
Re: Sapling weeks 5/6 Question 4
Hi! I believe the question is simply asking how closely the expected values match the observed ones. If the bond has “ample” character of the expected, then it would show bond lengths only somewhat similar to the specified observed; if the bond has “overwhelming” character of the expected, then it w...
- Sun Nov 15, 2020 6:35 pm
- Forum: Ionic & Covalent Bonds
- Topic: Hydrogen Bonding
- Replies: 13
- Views: 440
Re: Hydrogen Bonding
Hi! To my understanding, it is the combination of electronegativity and size that allow N, O, and F specifically to form hydrogen bonds. F, O, and N are some of the elements with the greatest electronegativity, and they are also unique in that they have relatively small sizes compared to other also-...
- Sun Nov 08, 2020 8:28 pm
- Forum: Trends in The Periodic Table
- Topic: Tips for learning the trends in the Periodic table
- Replies: 11
- Views: 706
Re: Tips for learning the trends in the Periodic table
Hi! Like others have mentioned above, I personally try to understand the concepts to apply when looking at the periodic table, but for memorization, I just stick to general directions on the period table. For example, as you move upwards and to the right on the periodic table, the atomic radius beco...
- Sun Nov 08, 2020 8:25 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Effective Nuclear Charges Between Orbitals
- Replies: 3
- Views: 264
Re: Effective Nuclear Charges Between Orbitals
Hi! I believe that electrons in 3d would have a greater effective nuclear charge than electrons in the 4s orbital, because as electrons exist in energy levels farther away from the nucleus, the greater distance reduces the attraction. So in the case of scandium, the electron in 3d should experience ...
- Sun Nov 08, 2020 8:22 pm
- Forum: Quantum Numbers and The H-Atom
- Topic: ml and number of possible electrons
- Replies: 6
- Views: 227
Re: ml and number of possible electrons
Hi! I believe you are right. When ms is not specified, there will be two possible electrons with the same ml quantum number, as ms refers to the electron spin (either up or down).
- Sun Nov 08, 2020 8:19 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: 4s before 3d Orbital
- Replies: 11
- Views: 544
Re: 4s before 3d Orbital
Hi! Like other people have said, I believe that this means that the electrons fill up the 4s orbital before the 3d orbital because 4s has lower energy than 3d. Hope this helps!
- Sun Nov 08, 2020 7:10 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: The orbitals
- Replies: 8
- Views: 574
Re: The orbitals
Hi! I believe that of all the information we are responsible for regarding orbitals, we especially need to be familiar with information like the number of orbitals in s/p/d/f, the location of the spdf blocks on the periodic table, etc.
As for 2s, the 2 refers to the 2nd energy level, and the s refe...
- Sun Nov 01, 2020 9:39 pm
- Forum: Photoelectric Effect
- Topic: N initial vs. N final
- Replies: 7
- Views: 364
Re: N initial vs. N final
Hi! Yes, it depends on whether the electron is emitting or absorbing energy; if it is emitting energy, the electron will drop energy levels, and if it is absorbing energy, the opposite will be true. To identify the initial energy state, consider whether we know if we are referring to the Lyman or Ba...
- Sun Nov 01, 2020 9:36 pm
- Forum: DeBroglie Equation
- Topic: Sapling Week 2-4 HW Question 24
- Replies: 11
- Views: 581
Re: Sapling Week 2-4 HW Question 24
Hi! I think that the bottom two in the right column would not be compatible—in order for the wave patterns to be compatible, they should be continuous and consistent in amplitude and wavelength. I try to imagine copy-pasting the graphs side by side to see if it would create a function resembling a s...
- Sun Nov 01, 2020 9:32 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Sapling #24
- Replies: 16
- Views: 545
Re: Sapling #24
Hi! I believe that for the wave patterns to be compatible, they must be continuous and consistent in amplitude/wavelength. Personally, I imagined copy-pasting the graph side by side; if this would create a continuous and consistent function resembling a sin function, it would be compatible.
- Sun Nov 01, 2020 9:28 pm
- Forum: Electron Configurations for Multi-Electron Atoms
- Topic: Ionic Radius
- Replies: 6
- Views: 245
Re: Ionic Radius
Hi! I believe that the ionic radius simply refers to the distance between the nucleus and outermost electrons. For ionic compounds made up of two or more different kinds of ions, this definition should still hold true.
- Sun Nov 01, 2020 9:23 pm
- Forum: Trends in The Periodic Table
- Topic: Tips for remembering
- Replies: 14
- Views: 659
Re: Tips for remembering
Hi! Personally, I just memorize the trend directionally; as you move to the right and upwards on the periodic table, the atomic radius decreases. The opposite is true for electron affinity and ionization energy.
- Sun Oct 25, 2020 1:54 am
- Forum: DeBroglie Equation
- Topic: Textbook Question 1B.15
- Replies: 6
- Views: 336
Re: Textbook Question 1B.15
Hi! I think the question is just asking for the energy work function, given that the frequency is 2.50 x 10^16 Hz. To solve for the energy, you would probably just use E = hv.
- Sun Oct 25, 2020 1:46 am
- Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
- Topic: Amplitude
- Replies: 16
- Views: 739
Re: Amplitude
Hi! I don’t believe that amplitude is related to frequency or wavelength. To my understanding, increasing amplitude simply means increasing intensity.
- Sun Oct 25, 2020 1:44 am
- Forum: Photoelectric Effect
- Topic: Photoelectric Effect Problem
- Replies: 6
- Views: 563
Re: Photoelectric Effect Problem
Hi! I’m not entirely sure because I used a different approach than the ones described above, but I got the same answer as Xinyu^. These were my steps: 1. Convert the work function from eV to joules (1.7624x10^-19 J). 2. Use the wavelength of the incident light to solve for the frequency of the incom...
- Sun Oct 25, 2020 1:25 am
- Forum: Einstein Equation
- Topic: Textbook Problem 1A.3
- Replies: 9
- Views: 491
Re: Textbook Problem 1A.3
^ Hi! I believe the correct answer should be C because frequency in EM radiation refers to the number of cycles that occur within a given amount of time. If the frequency decreases, there are fewer cycles taking place in this interval of time and the waves broaden. Thus, the extent of change that ha...
- Sun Oct 25, 2020 1:19 am
- Forum: Properties of Light
- Topic: Textbook Question 1A.5
- Replies: 5
- Views: 220
Re: Textbook Question 1A.5
Hi! I’m not sure about memorizing all the specific wavelengths/frequencies, but I think it would probably be helpful to know at least the order of the EM spectrum, and perhaps a general estimate of wavelengths in the context of the Lyman and Balmer series.
- Sun Oct 18, 2020 3:24 pm
- Forum: Photoelectric Effect
- Topic: Light Intensity
- Replies: 23
- Views: 568
Re: Light Intensity
Hi! Yes, I believe that it was only the brightness (intensity) of the light that was increasing, not the actual frequency/wavelength.
- Sun Oct 18, 2020 3:22 pm
- Forum: DeBroglie Equation
- Topic: Names of equations
- Replies: 8
- Views: 336
Re: Names of equations
Hi! I’m not sure that we need to memorize the names of the equations—I believe they are given. However, it’s probably a good move to be familiar enough with each one to be able to quickly identify and apply them if the question asks for a specific one.
- Sun Oct 18, 2020 3:18 pm
- Forum: Einstein Equation
- Topic: m vs nm
- Replies: 66
- Views: 3696
Re: m vs nm
Hi! I believe either is fine, unless the question specifically asks for one over the other. As others have said, though, I think many of the test questions will be multiple choice, so it might not be an issue at all.
- Sun Oct 18, 2020 3:16 pm
- Forum: Student Social/Study Group
- Topic: How are you studying?
- Replies: 204
- Views: 20924
Re: How are you studying?
Hi! I was planning on taking notes as I watched the lectures and then annotating my notes after all the lectures to see which parts I am least familiar with. (Unfortunately, my iPad deleted all my notes so now I have no lecture notes to review.) I think that doing practice problems is the most effec...
- Sun Oct 18, 2020 3:11 pm
- Forum: Properties of Light
- Topic: Energy from shorter wavelength
- Replies: 5
- Views: 268
Re: Energy from shorter wavelength
Hi! To my understanding, the higher energy of a shorter wavelength refers to the energy of the photon :)
- Fri Oct 09, 2020 11:31 pm
- Forum: SI Units, Unit Conversions
- Topic: Kg to g
- Replies: 13
- Views: 2401
Re: Kg to g
Hi! In order to calculate between kilograms and grams by hand, you can multiply by the conversion factor of 1 kg/1000 g or 1000 g/1 kg. You can think about it in terms of canceling out units. So to go from kg to g, we would multiply by (1000 g/1 kg); to go from g to kg, we would multiply by (1 kg/10...
- Fri Oct 09, 2020 12:39 am
- Forum: Balancing Chemical Reactions
- Topic: Naming compounds
- Replies: 21
- Views: 1369
Re: Naming compounds
Hi! I don’t think we are required to know how to name and identify compounds for exams just yet (based on what Dr. Lavelle mentioned before), but it would probably be helpful to brush up on some basic nomenclature anyway :)
- Fri Oct 09, 2020 12:34 am
- Forum: Limiting Reactant Calculations
- Topic: Limiting reactants in all chemical rxns?
- Replies: 18
- Views: 652
Re: Limiting reactants in all chemical rxns?
Hi! I think it would be extremely improbable for a chemical reaction to not have a limiting reactant. To do so would require having exact quantities of reactants that perfectly align with the stoichiometric ratios in a given equation, and reaching this point of precision is pretty unlikely. As such,...
- Fri Oct 09, 2020 12:30 am
- Forum: Accuracy, Precision, Mole, Other Definitions
- Topic: Moles vs molecules
- Replies: 14
- Views: 933
Re: Moles vs molecules
Hi! Molecules are atoms that are bound together in a group. A mole is essentially a unit representing set quantity of anything (6.022x10^23 “things”).
- Fri Oct 09, 2020 12:15 am
- Forum: SI Units, Unit Conversions
- Topic: Sig figs and molar mass
- Replies: 18
- Views: 623
Re: Sig figs and molar mass
Hi! Like others, I’ve been using as many decimal points as detailed in the period table posted on the class website. I assume that that is the periodic table we use for this class, so I stick to those values.