CHEMISTRY COMMUNITY

Malia Rose 1C

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...

Malia Rose 1C

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!

Malia Rose 1C

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.

Malia Rose 1C

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.

Malia Rose 1C

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.

Malia Rose 1C

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...

Malia Rose 1C

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!

Malia Rose 1C

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...

Malia Rose 1C

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.

Malia Rose 1C

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...

Malia Rose 1C

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...

Malia Rose 1C

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...

Malia Rose 1C

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...

Malia Rose 1C

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!

Malia Rose 1C

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?

Malia Rose 1C

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...

Malia Rose 1C

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...

Malia Rose 1C

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 ...

Malia Rose 1C

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 :(

Malia Rose 1C

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?

Malia Rose 1C

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?

Malia Rose 1C

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.

Malia Rose 1C

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

Malia Rose 1C

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

Malia Rose 1C

How does adding a catalyst increase the rate of the forwards and the reverse reaction?

Malia Rose 1C

Why are the signs of E knot and G knot opposite signs?

Malia Rose 1C

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?

Malia Rose 1C

omg well needed right now, I always watch the little mermaid for familiarity and it calms me down :))) yay Disney movies

Malia Rose 1C

What do integrated rate laws tell us? Why dont reactants have a one to one effect on reaction rate?

CHEMISTRY COMMUNITY

Search found 29 matches

constant k?

Catalysts in Reaction Mechanisms

Re: difference between E and Ecell naught

Re: Isolated Systems

Re: Galvanic cell and salt bridge

Re: Galvanic cell and salt bridge

Re: Redox reaction

Re: differential rate and integral rate

Re: Formula Sheet

Re: Polyprotic acid Exception

Re: Determining the Cathode and Anode in Concentration Cells (Textbook 6N.17-18)

Re: Determining the Cathode and Anode in Concentration Cells (Textbook 6N.17-18)

Re: Entropy

Bond Enthalpies

Exothermic vs. Endothermic Reactions

Work signs

Calculating Q using electrodes

Rate Law vs. Integrated Rate Laws

Integrated Rate Laws

relationship between pH and pKa

clarification question on pKa and pH

Re: Saying Thank You to Dr. Lavelle

Re: Fav Candy

Re: Fave food

Catalysts and reaction rates

signs of Gknot and Eknot

Equation logistics

Re: Comfort Movies

Rate Laws