Search found 29 matches
- Sun Mar 19, 2023 1:59 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: constant k?
- Replies: 3
- Views: 476
constant k?
Hi, I'm a little confused, in rate laws we assumed that k is constant in order to help us find concentrations using rates or initial concentrations, but why does it change in the Arrhenius equation? It changes with temperature and activation energy, so are we assuming that the experiments that we're...
- Sun Mar 19, 2023 1:56 am
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Catalysts in Reaction Mechanisms
- Replies: 4
- Views: 637
Catalysts in Reaction Mechanisms
Hi, does anyone know if catalysts are part of reaction mechanisms and if we're expected to verify reaction mechanisms on the final? Catalysts are like intermediates except they are consumed and then recreated yet not in the overall reaction, right? Thank you!
- Sun Mar 19, 2023 1:41 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: difference between E and Ecell naught
- Replies: 6
- Views: 1410
Re: difference between E and Ecell naught
E (non-standard cell voltage) will change over the course of the reaction (decreases and approaches 0), while Eo will not change and only represents the electrodes at standard conditions and molarities.
- Sun Mar 19, 2023 1:39 am
- Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
- Topic: Isolated Systems
- Replies: 5
- Views: 507
Re: Isolated Systems
It's also good to note that the change in total energy (delta U) will always be 0 as well for an isolated system because neither energy done by work or energy from heat (q) can be exchanged.
- Sun Mar 19, 2023 1:35 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic cell and salt bridge
- Replies: 3
- Views: 531
Re: Galvanic cell and salt bridge
Small add-on, a porous disc between the solutions would also have the same purpose, which is ion transfer between the solutions that would allow the solutions to stay neutral.
- Sun Mar 19, 2023 1:34 am
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Galvanic cell and salt bridge
- Replies: 3
- Views: 531
Re: Galvanic cell and salt bridge
Hi, the salt bridge connects the two sides of the cell in order to keep the charge constant on each side. On the anode side, when the metal oxidizes and gains a positive charge as it diffuses into the solution, the salt bridge diffuses negatively charged Cl- ions in order to restore that constant ch...
- Sun Mar 19, 2023 1:30 am
- Forum: Balancing Redox Reactions
- Topic: Redox reaction
- Replies: 3
- Views: 503
Re: Redox reaction
For acidic conditions, you would first balance the Oxygen in the equation with H2O, then balance the Hydrogen with H+. If the solution is basic, you'd then add OH- ions to each side to remove any remaining H+ ions and create H2O molecules, which can be canceled out on each side. Hope this helps!
- Sun Mar 19, 2023 12:23 am
- Forum: Zero Order Reactions
- Topic: differential rate and integral rate
- Replies: 3
- Views: 695
Re: differential rate and integral rate
Hi! I think a good way to remember when to use the differential or integral rate laws is based off the information you're given. The integrated rate law involves the initial concentration in the equation, which the differential doesn't include. Both come from the normal rate law, which doesn't inclu...
- Sun Mar 19, 2023 12:14 am
- Forum: Administrative Questions and Class Announcements
- Topic: Formula Sheet
- Replies: 1
- Views: 210
Re: Formula Sheet
I'm mentally remembering that for the integrated rate laws and half lives at the bottom of the equation sheet, the first three are for 1st order reactions, the next 3 are for 2nd order reactions, and the three after that are for 0 order reactions.
- Sun Mar 19, 2023 12:12 am
- Forum: Polyprotic Acids & Bases
- Topic: Polyprotic acid Exception
- Replies: 2
- Views: 419
Re: Polyprotic acid Exception
Hi, from what we went over in section, our TA said that for weak polyprotonic acids, we use the first Ka for the first deprotonation to find the pH, and that further deprotonation is insignificant. For strong polyprotonic acids, the first deprotonation is complete (ie polyprotonic acid H2A will full...
- Sat Mar 18, 2023 11:59 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Determining the Cathode and Anode in Concentration Cells (Textbook 6N.17-18)
- Replies: 4
- Views: 534
Re: Determining the Cathode and Anode in Concentration Cells (Textbook 6N.17-18)
A little add-on, you can also think of the higher concentration of positively-charged solution as having a "higher electron pulling power) since there's a greater concentration of positive ions on that side. This should help when choosing which is the anode and which is the cathode, as electron...
- Sat Mar 18, 2023 11:56 pm
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: Determining the Cathode and Anode in Concentration Cells (Textbook 6N.17-18)
- Replies: 4
- Views: 534
Re: Determining the Cathode and Anode in Concentration Cells (Textbook 6N.17-18)
Hi! In concentration cells, we assume that the side with the lower concentration is the product and anode. Electrons flow from the lower concentration (anode), releasing more Ag+ (aq) into the anode solution and causing more Ag+ (aq) to reduce on the cathode side into solid Ag, increasing the concen...
- Sat Mar 18, 2023 11:51 pm
- Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
- Topic: Entropy
- Replies: 4
- Views: 544
Re: Entropy
Hi!! Total entropy (of the universe) should increase for spontaneous processes because the positive change in entropy should outweigh the negative change. Take for example, the spontaneous reaction of hot metal releasing heat energy into the colder water around it. We assume that the heat, q, that t...
- Sat Mar 18, 2023 10:59 pm
- Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
- Topic: Bond Enthalpies
- Replies: 8
- Views: 572
Bond Enthalpies
Hi, quick question, in the tables we'll be given, bond enthalpies will always be positive because they represent the energy required to break bonds, right? Bond enthalpies in tables shouldn't be negative, and if they are, do they represent energy released? Thank you in advance!
- Sat Mar 18, 2023 9:29 pm
- Forum: Kinetics vs. Thermodynamics Controlling a Reaction
- Topic: Exothermic vs. Endothermic Reactions
- Replies: 5
- Views: 2422
Exothermic vs. Endothermic Reactions
Hi, in Kinetics, are we specifically only studying endothermic reactions and their rate laws, since I remember Dr. Lavelle saying that we add heat to speed up a forward reaction and cool it down to make the reverse reaction faster? How would we distinguish endothermic versus endothermic in kinetics?
- Sat Mar 18, 2023 9:17 pm
- Forum: Calculating Work of Expansion
- Topic: Work signs
- Replies: 5
- Views: 847
Work signs
Hi just a clarification question, when the system does work against the external pressure, meaning the piston moves outwards, this means the work, or more specifically the energy done by work, is negative? The system loses energy, but the work the system does is negative? Is that the correct interpr...
- Sat Mar 18, 2023 8:49 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Calculating Q using electrodes
- Replies: 1
- Views: 538
Calculating Q using electrodes
Hi, I'm working on a practice problem that states, "A tin electrode in 0.015 M Sn(NO3)2 (aq) is connected to a hydrogen electrode in which the pressure of H2 is 1.0 bar. If the cell potential is 0.061 V at 25 C, what is the pH of the electrolyte at the hydrogen electrode?" I understand tha...
- Sat Mar 18, 2023 5:10 pm
- Forum: General Rate Laws
- Topic: Rate Law vs. Integrated Rate Laws
- Replies: 9
- Views: 1542
Rate Law vs. Integrated Rate Laws
Hi, just wanted to get some more clarification between these two concepts. I know that you integrate the regular Rate Law (ie. rate= k[A]^2) to get the Integrated Rate Law, which adds time as a variable in the equation, but I'm a little unsure when to use each one. Is the regular Rate Law easier to ...
- Sat Mar 18, 2023 4:57 pm
- Forum: General Rate Laws
- Topic: Integrated Rate Laws
- Replies: 6
- Views: 857
Integrated Rate Laws
Hi, just a clarification question, are the integrated rate laws (when the rate laws become functions of time) the equations that produce the straight line graphs over time? The independent variable would be time and the dependent variable would be some form of [A] right? Hope I worded this clearly :(
- Fri Mar 17, 2023 3:58 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: relationship between pH and pKa
- Replies: 2
- Views: 339
relationship between pH and pKa
Can someone explain exactly why when pKa>pH, the protonated species (HA) will be more present than the deprotonated (A-) species? Is there a mathematical or conceptual reason for this?
- Fri Mar 17, 2023 3:56 pm
- Forum: Applying Le Chatelier's Principle to Changes in Chemical & Physical Conditions
- Topic: clarification question on pKa and pH
- Replies: 2
- Views: 313
clarification question on pKa and pH
Hi, after today's review session during class I was a little confused, so both Ka * Kb and [H3O+]*[OH-] =10^-14 right, but they're not the same values. Maybe I just don't understand the concept of Ka and Kb that well? Can someone confirm if these are right?
- Fri Mar 17, 2023 3:46 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 490
- Views: 984927
Re: Saying Thank You to Dr. Lavelle
Thank you Dr. Lavelle for all your smiles and your dancing and your beats and your jokes and your motivation throughout the quarter. You're an amazing teacher and I'm so glad I got to be in your class.
- Fri Mar 17, 2023 3:43 pm
- Forum: Student Social/Study Group
- Topic: Fav Candy
- Replies: 40
- Views: 2922
Re: Fav Candy
my favorite candy,,,, I need you all to remember gobstoppers. like the old halloween candy. they're so good. petition to bring them back into the public sphere
- Fri Mar 17, 2023 3:41 pm
- Forum: Student Social/Study Group
- Topic: Fave food
- Replies: 266
- Views: 76141
Re: Fave food
gonna be honest.... my comfort food is literally just white rice. also I really like eating frozen fruit with chopsticks. everyone try it sometime I promise it'll change your life
- Fri Mar 17, 2023 3:33 pm
- Forum: *Enzyme Kinetics
- Topic: Catalysts and reaction rates
- Replies: 4
- Views: 937
Catalysts and reaction rates
How does adding a catalyst increase the rate of the forwards and the reverse reaction?
- Fri Mar 17, 2023 3:15 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: signs of Gknot and Eknot
- Replies: 5
- Views: 638
signs of Gknot and Eknot
Why are the signs of E knot and G knot opposite signs?
- Fri Mar 17, 2023 2:51 pm
- Forum: Gibbs Free Energy Concepts and Calculations
- Topic: Equation logistics
- Replies: 2
- Views: 421
Equation logistics
Sometimes I forget when we are going to do reactants- products or products-reactants? Can anyone help me figure out which scenarios lead to each?
- Fri Mar 17, 2023 2:43 pm
- Forum: Student Social/Study Group
- Topic: Comfort Movies
- Replies: 168
- Views: 78942
Re: Comfort Movies
omg well needed right now, I always watch the little mermaid for familiarity and it calms me down :))) yay Disney movies
- Fri Mar 17, 2023 2:41 pm
- Forum: General Rate Laws
- Topic: Rate Laws
- Replies: 1
- Views: 89
Rate Laws
What do integrated rate laws tell us? Why dont reactants have a one to one effect on reaction rate?