CHEMISTRY COMMUNITY

Yutian Zhao -1J

in the concentration cell, why do we always make the side with lower concentration the product? I am a little bit confused. How do we derive that? Thanks.

Yutian Zhao -1J

Yes, I think we should. We can derive the rate law by setting unique reaction rate of R on the left side while k*[R]^n on the right side. Hope it helps.

Yutian Zhao -1J

An intermediate is a product in the former step and is consumed as a reactant in later step(s). And it won't show up in the overall reaction equation. Hope it helps.

Yutian Zhao -1J

yes, i believe so. Aldehydes is the one with C bonded to one or two H, and Ketones is the one with C bonded to two C. I think they share the structure "C=O" where two atoms can be bonded to the left of the C to make a total of four bonds around C. Hope it helps.

Yutian Zhao -1J

according to unique reaction rate law: -(1/a)*delta[A]/delta t= (1/b)*delta[B]/delta t, we can cancel delta t on both sides since they are the same, then we know that a=2, b=1, and we also know delta[B] =0.034mol/L since [B]initial is zero. Then we can derive delta[A] from the equation. since we als...

Yutian Zhao -1J

I don't believe we need to know the half-life reaction of third or fourth order reaction. But we should be able to tell if it is a third or fourth order reaction based on the experimental data that are given. Hope it helps.

Yutian Zhao -1J

you can write the rate law (with units) first and then cancel units on both sides, then whatever units that are not cancelled should be the units of k. the units of k depends on the order of reaction. And pay more attention when writing the rate law if any concentration is to be squared (or higher),...

Yutian Zhao -1J

As the slowest step always determines the overall reaction, find the elementary step whose rate law is the same as the overall reaction rate law, then that elementary step would be the slowest and be the rate determining step. Hope it helps.

Yutian Zhao -1J

But how are we supposed to know whether the rxn is spontaneous or not?

Yutian Zhao -1J

same question. I noticed that some cell diagrams put reactant of the half-rxn first and then product, while others put product of the half-rxn first and then reactant. Just want to know whether the order matters. And how are we supposed to know which is the reactant and which is product in the half-...

Yutian Zhao -1J

PranithaPrasad wrote:that

Thank you! But i am wondering about the "O2(g)|H+(aq)" part. I didn't find anything related to this part back in appendix. I think is should be O2|H2O?

Yutian Zhao -1J

for the cell diagram (e.g., a|b||c|d ) if we know that the left side of the salt bridge represents oxidation and the right side represent reduction, does "a" have to be the reactant and "b" be the product of the oxidation half-reaction? Or is there any way to figure out which is ...

Yutian Zhao -1J

But why can't we assume the reduction of O3 to BrO3-? I thought the oxidation number would then be decreased from 0 to -2. Can the BrO3- be a product of both oxidation and reduction? I am a little bit confused.

Yutian Zhao -1J

salt bridges are designed to make a complete electrical circuit. Without the salt bridges, as anode keeps losing e-, it becomes less negative, and as cathode keeps accepting e-, it becomes less positive; after a period of time, anode and cathode go to equilibrium and become neutral where no e- will ...

Yutian Zhao -1J

thanks!!

Yutian Zhao -1J

when we are asked to calculate the standard reaction S/H/G, does the stoichiometric coefficient of one product must be 1? Or we can calculate these standard reaction entropy/enthalpy/ free energy just by balancing the reaction regardless of the product's stoichiometric coefficient ? Since in 9.59, t...

Yutian Zhao -1J

in the hw 9.47b, why does the delta S of surroundings equal 0? why does work=0? Can somebody help me with this? thanks!

Yutian Zhao -1J

For the reversible process, I personally believe that professor Lavelle just wanted to emphasize that the transfer of e- for each step is very small, which makes the potential difference change slowly. And it doesn't mean that the flow of e- is reversible I guess. But I am not sure if my answer is c...

Yutian Zhao -1J

You can calculate the entropy change resulting from temp change and volume change together separately and then add them up. Use delta S=nRln(v2/v1) to calculate the detla S for volume change and then use detlaS=nCln(T2/T1) to get the entropy change for temp change.

Yutian Zhao -1J

same question!

Yutian Zhao -1J

"Calculate the standard entropy of vaporization of water at 85 C, given that its standard entropy of vaporization at 100. C is 109.0 J K 1 mol 1 and the molar heat capacities at constant pressure of liquid water and water vapor are75.3 J K 1 mol 1 and 33.6 J K 1 mol 1, respectively, in this ran...

Yutian Zhao -1J

in the lecture, for the last example to calculate the W of BFCl2, if there are four moles of this molecules, does that mean w= 3^4NA? and therefore S=4Rln3? I am a little bit confused. Thanks!

Yutian Zhao -1J

So for the last example of BFCl2, if there are 4 moles of this molecules, then does w=3^4NA? or just w=3^4?

Yutian Zhao -1J

In today's lecture, professor Lavelle mentioned that for an isolated system (constant energy) at equilibrium, W is maximum. Does anyone know why it is maximum? Thanks.

Yutian Zhao -1J

according to U=q+w, under constant P(delta H=qp),when there is an expansion, work is done by the system, therefore w=-P*delta V (P is constant so only V changes, and since work is done by the system, there is a negative sign in the front); and: U=q+w =delta H+w =delta H+(-P*delta V) =delta H- P*delt...

Yutian Zhao -1J

According to U=q+w, under constant pressure (deltaH=q),U=delta H+w. With that being said, the internal energy equals sum of enthalpy change and the work done by/on the system.

Yutian Zhao -1J

How should we solve this problem? I am super confused. Why does it have to do with PV=nRT?

Yutian Zhao -1J

A bomb calorimeter is the one with constant V, while the simple calorimeter is just the one with constant P and not sealed.

Yutian Zhao -1J

Since Professor Lavelle would cover topics in the order listed in outline, then if we read the textbook by following the lecture materials, there would be lots of things that we haven't learnt and are related to the previous parts. Should we pass them or read from the beginning of Chapter 8 by ourse...

Yutian Zhao -1J

The ice would be the system, and the hand would be its surroundings. When the ice absorbs energy(heat) and reaches to its melting point, it melts, therefore the heat absorbed comes from surroundings, and the phase change is endothermic, and the hand that loses heat would cool down.

CHEMISTRY COMMUNITY

Search found 30 matches

concentration cell

Re: Deriving rate laws?

Re: Intermediate

Re: Carbonyl -> Aldehydes and Ketones [ENDORSED]

Re: 15.23 c

Re: 3rd order, 4th order, etc.

Re: Units of k

Re: Which Step is Slower?

Re: Anodes vs. Cathodes

Re: Order in Cell Diagrams

Re: cell diagram (hw14.11)

cell diagram (hw14.11)

Re: 14.5

Re: Salt Bridges

Re: hw9.59 standard reaction entropy

hw9.59 standard reaction entropy

hw9.47b

Re: Max Potential

Re: Change in vol and temp

Re: q(REV)

homework 9.19

W for BFCl2 in the lecture example

Re: N: number of particle [ENDORSED]

W(degeneracy) in isolated system [ENDORSED]

Re: Enthalpy Equation

Re: Internal Energy

hw 8.49

Re: What type of system is a Bomb Calorimeter?

reading textbook

Re: Endothermic Reaction