gen chem question

[rmm30]

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so im picking out problems at random and have come across several rate law questions asking you to calculate the rate law of a rxn that has an initial FAST step with subsequent slow step/s. i dont recall how to do these (as there are a ton of calculations involved) and im wondering if anybody knows if this is fair game for DAT. I haven't seen it in barrons,kbb, and a couple others. any help appreciated

 

[nyr201]

so im picking out problems at random and have come across several rate law questions asking you to calculate the rate law of a rxn that has an initial FAST step with subsequent slow step/s. i dont recall how to do these (as there are a ton of calculations involved) and im wondering if anybody knows if this is fair game for DAT. I haven't seen it in barrons,kbb, and a couple others. any help appreciated

well u can figure out the rate law from the slow step (since its the rate determining step) so if its given, its very easy...u look at the slow step and see how many reactants there are if 2 reactants then its a 2nd order rxn 1 reactant then its a 1st order. Only when ur given a net rxn and no mechanism for it, can u not determine rate law without experimental data.

Although i didn't see this on my DAT im sure its fair game bc its a quick and simple questions to ask. should take u total of 10 seconds to answer.

hope this answers ur question.

 

[rmm30]

thanks nyr for the response and way to go the real thing! im still confused though for rate law w. initial fast steps. if i remember correctly you have to invert some of the elementary rxns but i will prob have to consult that chapter from my text. unless of course this is not covered on DAT. solving one of these baby's is such a bitch so i think i will just skip this. haven't seen this spec type in any dat prep book yet.

 

[DoCt0rPeTe]

thanks nyr for the response and way to go the real thing! im still confused though for rate law w. initial fast steps. if i remember correctly you have to invert some of the elementary rxns but i will prob have to consult that chapter from my text. unless of course this is not covered on DAT. solving one of these baby's is such a bitch so i think i will just skip this. haven't seen this spec type in any dat prep book yet.

I'd say the only thing you'll see on the DAT is to determine the rate law from a Slow step ONLY IF ITS THE FIRST STEP. If its a step after the first step, stoichiometry is not going to work....it gets alot more complex as you said.
Don't waste your time though...unless you have a good amount of time.

 

[rmm30]

thanks for response pete. i think the collective paranoia of this forum is starting spread to my brain. i start studying in the morning the topics most tested on DAT and when i get in my textbooks i seem to get sucked in further and further to subject matter that i know wont be covered. This happens alot with ochem. its a like a compulsion to cover even the most absurd topics in a quest to cover all possibilities. when this happens i feel like i lose touch with the fundamentals that i have to be strong in.

 

[nyr201]

I'd say the only thing you'll see on the DAT is to determine the rate law from a Slow step ONLY IF ITS THE FIRST STEP. If its a step after the first step, stoichiometry is not going to work....it gets alot more complex as you said.
Don't waste your time though...unless you have a good amount of time.

👍 sorry forgot to add that bit abt the first step lol. that's kinda important right? LOL

good luck rmm, GC is very doable on the DAT, practice ur calculation set ups, destroyer can help great with this.

 

[DQLEUCD]

so im picking out problems at random and have come across several rate law questions asking you to calculate the rate law of a rxn that has an initial FAST step with subsequent slow step/s. i dont recall how to do these (as there are a ton of calculations involved) and im wondering if anybody knows if this is fair game for DAT. I haven't seen it in barrons,kbb, and a couple others. any help appreciated

Rate Law questions will be given in experimental data. There is no way to determine the rate law otherwise. It's where you have you have [A] change while is the same and have the rate for it and solve. With the rate law figured, you can find k.

Also know the units of the rate law depending if it's 0 order to 5th order and the graphs of 0 order, 1st order and 2nd order.