# AAMC SB C/P 26

#### PagingDr.F

2+ Year Member
This is a relatively easy problem to solve but now I'm confused about when to use Avos.#

If it's asking for how many molecules, don't you have to multiply by Avos.#?

lol t-minus 3 days till test and THIS is what I'm confused about...

OP
P

#### PagingDr.F

2+ Year Member
Well...all the answers are in mols so...whatever I guess...?

#### aldol16

2+ Year Member
mol is a unit. Like "dozen" actually. How many donuts do you want? Two dozen. How many molecules do you want? 1 mole (of molecules).

OP
P

#### PagingDr.F

2+ Year Member
and what is the total number of donuts in a dozen? 12 donuts. What is the total number of molecules in a mole? 6.022*10^23 molecules.

I would hope anyone taking the MCAT understand what moles are but thanks lol

I've gotten practice Qs wrong before because I simply forgot to multiply by Avogadro's number but I realized all the answer choices were in moles so clearly I didn't have to (why I answered my own post).

#### JustinM88

2+ Year Member
maybe yall already pointed it out, but the question writer forgot to go that extra step in order to convert to molecules

#### aldol16

2+ Year Member
and what is the total number of donuts in a dozen? 12 donuts. What is the total number of molecules in a mole? 6.022*10^23 molecules.

I would hope anyone taking the MCAT understand what moles are but thanks lol
Then you still don't understand the question. It's not asking you "what is the total number of molecules in the x mol of ATP that hydrolyzed." It's asking you "what is the total number of ATP molecules that hydrolyzed." So while the total number of donuts in a dozen is indeed 12, when you answer a question asking "what is the total number of donuts consumed?" both "one dozen" and "twelve" are acceptable responses. The question writer didn't miss anything.

OP
P

#### PagingDr.F

2+ Year Member
both "one dozen" and "twelve" are acceptable responses.
This is true. But if someone asks for total number of molecules you should give an answer in molecules, no? Otherwise, why not just ask "how many moles of atp were hydrolyzed?"

For example, if asked for moles, would it then be okay to give an answer in molecules? By your reasoning it should be because X number of molecules is equivalent to Y number of moles, and both answers are acceptable.

I understand the question and I understand what moles are. I just think they should be more consistent. This is all semantics really...I'll just pay attention to the units used in the answer choices

#### aldol16

2+ Year Member
This is true. But if someone asks for total number of molecules you should give an answer in molecules, no? Otherwise, why not just ask "how many moles of atp were hydrolyzed?"
Not necessarily. If someone asks you how many donuts you want, are you obliged to give the answer in individual donuts? Or can you say "a dozen"? They could ask how many dozen donuts you want. In that case, you would just say "one dozen" or "two dozen" and not "twelve." I'm saying that this question is grammatically consistent with the answer choices.

OP
P

#### PagingDr.F

2+ Year Member
I argued that it wasn't consistent with other questions I've seen asking specifically for "molecules". See the pictures below for an example.

I've gotten practice Qs wrong before because I simply forgot to multiply by Avogadro's number

My original post indicated I understood what moles are because I was asking about avogadro's number (I.e., 1 mole = 6.022*10^23 molecules/atoms/etc.) Your reply was an explanation of what moles were and somewhat condescending.

For MCAT purposes, when they ask for molecules, they usually imply you must convert moles to molecules. Is it true that you can answer in moles? Yes you can, but it's not what was asked for.

Last edited:

#### aldol16

2+ Year Member
Yes, but what you're failing to understand is that it's not as simple as kilograms to grams. Again, use the donut example. If I ask you how many donuts you want, is it out of place to say "a dozen"? I obviously asked you how many individual donuts you want and you answered "a dozen." Is that acceptable? Is that out of place at all? A mole of molecules is a perfectly legitimate unit. If there was such a thing as a kilogram of grams, then your example would make sense. But there isn't.

OP
P

#### PagingDr.F

2+ Year Member
Okay, so when do you use Avogadro's number? When they ask you for what?

#### aldol16

2+ Year Member
Okay, so when do you use Avogadro's number? When they ask you for what?
They could have also given you the answer choices in number of molecules here. Like 1.2 x 10^23 molecules of ATP. When do you use 'dozen' and when do you use individual counts? It's an arbitrary decision in most cases. How many roses do you want? 'I want a dozen roses.' You could just as easily and accurately say 'I want twelve.'