HELP ME gain intuition for MCAT Gen Chem Calculations!!!!

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dennis-brodmann

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For General Chemistry MCAT questions that usually don't require number crunching, I typically do well. When there are calculations, especially in stoichiometry, my synapses just don't fire as fast as I wish they did.

I finished the stoichiometry section in TBR today and the last 14 discretes kicked my butt.
I got 4 out of 14 right (and on two of them I just guessed).

I have heard the MCAT is a very conceptual test that really forces you to think, but I need to prepare for the worst and master calculations of any sort.

My exam is on August 10 (34 days from today)...
For all of you who have been in my shoes and prevailed,
what are your suggestions?
 
For General Chemistry MCAT questions that usually don't require number crunching, I typically do well. When there are calculations, especially in stoichiometry, my synapses just don't fire as fast as I wish they did.

I finished the stoichiometry section in TBR today and the last 14 discretes kicked my butt.
I got 4 out of 14 right (and on two of them I just guessed).

I have heard the MCAT is a very conceptual test that really forces you to think, but I need to prepare for the worst and master calculations of any sort.

My exam is on August 10 (34 days from today)...
For all of you who have been in my shoes and prevailed,
what are your suggestions?

I got a 12 on my Physical Sciences section first round (retaking though). Is your issue that you can't do the calculations/don't know how to do the type of problems or that you're not understanding what they're asking of you?
 
Stoichiometry or dimensional analysis requires an essential understanding of units. If you can get the simple problems down, and its the lengthy calculations that are getting to you, then you just need to learn to take smarter risks at estimating and rounding numbers. The MCAT, sometimes unlike test prep books like TBR, is more generous in separation of answers to reward smart rounding. If you have the concepts down, I wouldn't worry too much about the numbers, just try to get an intuitive feel for ratios and such. For example, if you have a super complicated fraction like 437/93 ... round it to 450/90 or 5, and know its a little bit less than 5 since you rounded the numerator up and the denominator down.

I hope that helps and addresses what you were concerned about...

P.S. EK Verbal and Math book has a whole chapter on mathematical intuition and Kaplan has about half a chapter for it. TBR doesn't really focus on it, so you may want to try and expand your resources.

34 days is plenty of time, you can do it!!
 
I got a 12 on my Physical Sciences section first round (retaking though). Is your issue that you can't do the calculations/don't know how to do the type of problems or that you're not understanding what they're asking of you?

There are times when I don't understand what they're asking me; other times I come across a question and I have an idea on how to set the problem up, but I always tell myself "THAT'LL TAKE TOO LONG TO SOLVE IT THAT WAY!!!! YOU'RE OVERTHINKING IT!!!!". In your past experience, is that how some calculations go sometimes? That is, the only shortcut is the long and tedious route? lol

Stoichiometry or dimensional analysis requires an essential understanding of units. If you can get the simple problems down, and its the lengthy calculations that are getting to you, then you just need to learn to take smarter risks at estimating and rounding numbers. The MCAT, sometimes unlike test prep books like TBR, is more generous in separation of answers to reward smart rounding. If you have the concepts down, I wouldn't worry too much about the numbers, just try to get an intuitive feel for ratios and such. For example, if you have a super complicated fraction like 437/93 ... round it to 450/90 or 5, and know its a little bit less than 5 since you rounded the numerator up and the denominator down.

I hope that helps and addresses what you were concerned about...

P.S. EK Verbal and Math book has a whole chapter on mathematical intuition and Kaplan has about half a chapter for it. TBR doesn't really focus on it, so you may want to try and expand your resources.

34 days is plenty of time, you can do it!!

I'm usually good at estimating, but sometimes, the set up is what gets me. Sometimes just thinking about how to set up the problem, feels like an eternity that I could be using for other questions that may be harder. Like in my question for sciencebooks,
in your experience, do some problems just have multiple steps and there really is NO SHORTCUT? I always feel like there should be a shortcut though, since people have said on here that the calculations should be relatively simple.

For most passages in TBR, I set my countdown timer for as many questions as the passage has. For instance, if there are 5 questions, I set it for 5 minutes, which will include reading the passage first/analyzing diagrams, etc.
This is how I do all my science passages. For all the organic and biology sections, I do well to finish since there are barely an computations, but there are times in the physical science passages where I cut it too close and/or just have to make blind guesses. When I say "blind guesses", I mean I try to use process of elimination, but I don't feel secure. I guess that's how it is sometimes though....

sciencebooks and member232, do you think my timing goals are unrealistic?
Do you think I should set all my passages for the same time, 7 minutes? I set up my timer like this because I feel it will simulate the pressure I will have during the real exam and force me to think faster (if that's possible...I get kind of creative sometimes on my scratch paper haha).
 
There are times when I don't understand what they're asking me; other times I come across a question and I have an idea on how to set the problem up, but I always tell myself "THAT'LL TAKE TOO LONG TO SOLVE IT THAT WAY!!!! YOU'RE OVERTHINKING IT!!!!". In your past experience, is that how some calculations go sometimes? That is, the only shortcut is the long and tedious route? lol

I suppose some calculations are tedious in setting up the formula, but I think practice make that easier (it's just getting units to cancel out). I, for one, actually tended to have an issue with these questions too. Review your questions, do them until you know them (even with prior exposure, I know), and try to seek resources in your books. Watch out for traps and key words in the question: Always balance the equation first, always double check if you want mols or grams or THINGS (multiply by Avagadro's number), etc.

I'm usually good at estimating, but sometimes, the set up is what gets me. Sometimes just thinking about how to set up the problem, feels like an eternity that I could be using for other questions that may be harder. Like in my question for sciencebooks,
in your experience, do some problems just have multiple steps and there really is NO SHORTCUT? I always feel like there should be a shortcut though, since people have said on here that the calculations should be relatively simple.

For most passages in TBR, I set my countdown timer for as many questions as the passage has. For instance, if there are 5 questions, I set it for 5 minutes, which will include reading the passage first/analyzing diagrams, etc.
This is how I do all my science passages. For all the organic and biology sections, I do well to finish since there are barely an computations, but there are times in the physical science passages where I cut it too close and/or just have to make blind guesses. When I say "blind guesses", I mean I try to use process of elimination, but I don't feel secure. I guess that's how it is sometimes though....

sciencebooks and member232, do you think my timing goals are unrealistic?
Do you think I should set all my passages for the same time, 7 minutes? I set up my timer like this because I feel it will simulate the pressure I will have during the real exam and force me to think faster (if that's possible...I get kind of creative sometimes on my scratch paper haha).

I'd definitely work on timing from here on out, yes. I don't want you to ignore your weaknesses, but with a set amount of time, sometimes you have to accept them. I'd often skip some general chemistry stoichiometry questions and mark them for the end simply because I never they were a time suck for me and I'd rather do four questions than one like that. If you feel like going back to them with your leftover time will take some of the pressure off, that's an option.
 
I agree with what sciencebooks says, and I'd like to make a few more points:

1. If you're using TBR passages to gauge timing, keep in mind that they DO tend to be a bit more challenging than the majority of AAMC passages. I find myself taking the full 7-8 minutes for a lot of TBR passages, while some AAMC ones I can get done in 5 minutes. Keep in mind that the breakdown of the test, if you spend 1 minute per discretes, allows you 57 minutes for 7 passages. That is a little more than 8 minutes per passage. However, you are absolutely correct in trying to aim for a lower time per passage because of the stress of test day. I'm retaking and one of the reasons is because on Test Day I had this need to focus too much on q's that I got tripped a little by, trying to make sure I had the right answer since it was the "real deal" and spent almost 4 minutes on one of the discretes. This threw me off for the whole physical sciences section, simply because I did not treat the real MCAT the way I had practiced for it. So now in my prep, I force myself to move on once I hit 8 minutes per passage NO MATTER WHAT so that way i have extra time left over. The passages I dont have trouble with, I finish in less than 8 minutes anyways, adding to the time I have left over. If I were you, I would realistically aim for a cap of 7 minutes per passage. Like you said, some passages have 5 qs, while others have 8 qs, so you may even broaden this time range to 14 min/ 2 passages. I think this is a lot less stressful then going into a test, seeing how many qs there are per passage, and calculating how many minutes you can allow yourself per passage, and then when going over, freaking out (personal experience).

Also, if you have a little over a month left, if you haven't already started, you should be taking FL's soon. Take AAMC 3 and see how the calculations treat you. You should find them very straightforward and manageable.

And if you're still tripping up over how to set up questions, maybe take some time after you've done a passage, see which equation you were supposed to use, and mess around with the units until you derive the equations. For example, in the beginning, I was really weak at E/M. I took the equation F= kqq/r2 and messed around with the units until i understood how to to get V=Ed, V = kq/r, etc... It really helped in that case... See if it works for you?
 
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