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Invisibleshadyy
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chemistry help * 1
    #22266239 - 09/20/15 06:10 PM (8 years, 4 months ago)

My lab partner got most of the calculations...so....I have a feeling something is wrong, but I can't figure it out.

I'm trying to determine Avogadro's number using the volume, density and molar mass of carbon (all of which we got during the experiment).

volume of 1 C atom = 1.02x10^-22
density of C = 3.51g/cm^3
molar mass = 12.01

I'm coming up with 3.4x10^22
but avogoogoo's number is 6.022x10^23


I'm gonna give you all the calculations....

concentration of SA/hex soln. - 0.177g/L
volume of SA/hex solution in the monolayer - 0.299mL
density of SA - 0.85g/mL
radius of watch glass - 6.16cm

find the mass of stearic acid in the monolayer - 0.117/1000 x 0.299 = 2.68x10-5

find volume of stearic acid in the monolayer - 2.68x10^-5/0.85 = 3.2x10^-5

this is one I'm questioning---> find thickness (h) of the monolayer - 3.2x10^-5 = pi(6.16)^2h  = 1.046x10^-6

calculate radius of carbon atom - 1.046x10^-6/36 = 2.9x10^-8

find volume of one carbon atom - V=4/3pi(r)^3 = 1.02x10^-22

determine avogadro's number - 12.01/density/volume = 3.4x10^22

thanks


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OfflineHanz
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Re: chemistry help [Re: shadyy] * 1
    #22266305 - 09/20/15 06:23 PM (8 years, 4 months ago)

I didn't really check your whole calculation yet, but my first thought is: you are using the volume of the C atom, but C is really a mixture of isotopes. 10, 12 and 14 IIRC... Their different percentages give you the fractional molar mass, after all.

But is your volume an average for the different isotopes? Is it the correct average?

(Does this even matter anyway? Or do the different isotopes have identical volumes?)

Hope this helps... I may just be completely off here :shrug:

Love, Hanz.


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Invisiblevinsue
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Re: chemistry help [Re: shadyy] * 1
    #22266316 - 09/20/15 06:25 PM (8 years, 4 months ago)

I would say
:postscore:

:teacher: . . . :peace:


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OfflineHanz
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Re: chemistry help [Re: shadyy] * 1
    #22266359 - 09/20/15 06:33 PM (8 years, 4 months ago)

Quote:

i hate liz said:
this is one I'm questioning---> find thickness (h) of the monolayer - 3.2x10^-5 = pi(6.16)^2h  = 1.046x10^-6





Hmm... i don't get this one really...
what exactly are you trying to do here?
The way it reads now is that it says:

3.2x10^-5 = 1.046x10^-6

which can't be what you mean.

Also, I would expect you to mean pi(6.16)*2h instead of pi(6.16)^2h

I don't follow completely, elaborate please,

And describe what you want to do better, I can hardly follow what you intend to do,

Perhaps it's my lack of chemistry knowledge, but what is this monolayer, and what do you want of it?


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Invisibleshadyy
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Re: chemistry help [Re: Hanz] * 1
    #22266383 - 09/20/15 06:37 PM (8 years, 4 months ago)

Sorry,

V = pir^2h
3.2x10^-5 = pi(6.16)^2h <--solve for h
h = 1.046x10^-6

I'm getting a different answer than that, but that's what was recorded.

What I'm looking for is someone who can tell me if it's my data, or if I'm doing a calculation incorrectly.


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ga ga ga eets eets how you gone be mad on vacation?
MONICA COULDN'T TELL TIME UNTIL SHE WAS 13


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Invisiblemicro
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Re: chemistry help [Re: Hanz] * 1
    #22266424 - 09/20/15 06:47 PM (8 years, 4 months ago)

Okay so you have a solution of stearic acid....

Why are you determining this from a single carbon?

I mean, you have the density of stearic acid; can't you just change that to normality?

Also, for h it might help to know the size and shape of the container just to double check.


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Edited by micro (09/20/15 06:49 PM)


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OfflineHanz
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Re: chemistry help [Re: shadyy] * 1
    #22266444 - 09/20/15 06:52 PM (8 years, 4 months ago)

Oh, I get it

V =  pi * (r^2) * h  ... I read  V =  pi * r^(2h)  at first, .. LoL  .. made me :confused:

And you want this solved for h?
Well come on, easy to solve, basic math!
check the calculation, if it's correct, then your data is iffy.


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Small scale alternative parties rich in empathy and extravagance. Happen to know of one in the vicinity of Amsterdam? PM me my dear fellow. I love to meet some other freaks.

Oh and, if you can,.. embrace the nyctomorph. It needs you.


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Invisibleshadyy
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Re: chemistry help [Re: shadyy]
    #22266459 - 09/20/15 06:56 PM (8 years, 4 months ago)

nvm, caught it


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ga ga ga eets eets how you gone be mad on vacation?
MONICA COULDN'T TELL TIME UNTIL SHE WAS 13


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OfflineHanz
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Re: chemistry help [Re: shadyy]
    #22266489 - 09/20/15 07:02 PM (8 years, 4 months ago)

... is that a Won-Ton soup ?... I like those :awesomenod:


--------------------
Small scale alternative parties rich in empathy and extravagance. Happen to know of one in the vicinity of Amsterdam? PM me my dear fellow. I love to meet some other freaks.

Oh and, if you can,.. embrace the nyctomorph. It needs you.


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Invisiblemicro
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Re: chemistry help [Re: Hanz]
    #22266501 - 09/20/15 07:05 PM (8 years, 4 months ago)

glad you figured it out :3

still not sure how you can determine anything from one carbon atom without estimating bond lengths and accounting for H, O... but whatev


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Invisibleshadyy
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Re: chemistry help [Re: micro]
    #22266533 - 09/20/15 07:12 PM (8 years, 4 months ago)

yeah, I'm starting to think I didn't figure it out


I'm supposed to use the volume I calculated (of a single carbon atom), the molar mass of carbon and the density of carbon in a diamond to find the number of atoms in a mole.


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ga ga ga eets eets how you gone be mad on vacation?
MONICA COULDN'T TELL TIME UNTIL SHE WAS 13


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OfflineHanz
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Re: chemistry help [Re: micro]
    #22266548 - 09/20/15 07:16 PM (8 years, 4 months ago)

Quote:

micro said:
still not sure how you can determine anything from one carbon atom without estimating bond lengths and accounting for H, O... but whatev




:whathesaid:


--------------------
Small scale alternative parties rich in empathy and extravagance. Happen to know of one in the vicinity of Amsterdam? PM me my dear fellow. I love to meet some other freaks.

Oh and, if you can,.. embrace the nyctomorph. It needs you.


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Invisibleshadyy
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Re: chemistry help [Re: Hanz]
    #22266567 - 09/20/15 07:20 PM (8 years, 4 months ago)

god dammit


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ga ga ga eets eets how you gone be mad on vacation?
MONICA COULDN'T TELL TIME UNTIL SHE WAS 13


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InvisibleMalcolm_Xtasy
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Re: chemistry help [Re: shadyy]
    #22266630 - 09/20/15 07:33 PM (8 years, 4 months ago)

Quote:

i hate liz said:
My lab partner got most of the calculations...so....I have a feeling something is wrong, but I can't figure it out.

I'm trying to determine Avogadro's number using the volume, density and molar mass of carbon (all of which we got during the experiment).

volume of 1 C atom = 1.02x10^-22
density of C = 3.51g/cm^3
molar mass = 12.01

I'm coming up with 3.4x10^22
but avogoogoo's number is 6.022x10^23


I'm gonna give you all the calculations....

concentration of SA/hex soln. - 0.177g/L
volume of SA/hex solution in the monolayer - 0.299mL
density of SA - 0.85g/mL
radius of watch glass - 6.16cm

find the mass of stearic acid in the monolayer - 0.117/1000 x 0.299 = 2.68x10-5

find volume of stearic acid in the monolayer - 2.68x10^-5/0.85 = 3.2x10^-5

this is one I'm questioning---> find thickness (h) of the monolayer - 3.2x10^-5 = pi(6.16)^2h  = 1.046x10^-6

calculate radius of carbon atom - 1.046x10^-6/36 = 2.9x10^-8

find volume of one carbon atom - V=4/3pi(r)^3 = 1.02x10^-22

determine avogadro's number - 12.01/density/volume = 3.4x10^22

thanks



I think your value for density might be wrong. Since you're technically trying to find volume would you have to convert to g/L not cm^3?


--------------------
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I'm ugly, Enlil is beautiful.
I'm a loser, Enlil is a winner.
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Invisiblemicro
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Re: chemistry help [Re: Malcolm_Xtasy]
    #22266798 - 09/20/15 08:18 PM (8 years, 4 months ago)

1ml = 1cc

Looking it up:

Quote:

C-C bond length in diamond is 1.54AO. ... Its density is 3.5 gm/cm3




For stearic acid:

Quote:

average C - C bond length is 154 pm




So, maybe you are just supposed to use that?

Not sure how that accounts for van der waals forces but I guess it makes sense they are about equal.

If that's the case I wonder if using the same density would work. (accounting for the solvent, of course)

It would be an estimation even without van der waals forces but idk what else they'd want.


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Edited by micro (09/20/15 08:21 PM)


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Offlinefapjack
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Re: chemistry help [Re: shadyy]
    #22266973 - 09/20/15 08:50 PM (8 years, 4 months ago)

Ok lets see 1 mole of carbon is 12.01 grams  1 cc of carbon weighs 3.51 grams per cc, so 1 mole makes 3.42 cubic centimeters.  This is a pretty large value so lets convert that into angstrom.  3.42x10^24 cubic amstrom per 6.02x10^23 carbon atoms.  I'm getting 5.68 cubic amstrom per atom of carbon.  The actual radius for carbon is 1.54 which would make it 6.45 cubic amstrom so it is pretty close to the actual value.  In your experiment it will be 1.35‎Å though as 4/3pi*1.35=5.68Å


I don't really know what the other info is for and I'm tired so that is all I can help you with tonight.


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Edited by fapjack (09/21/15 03:00 PM)


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Offlinefapjack
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Re: chemistry help [Re: fapjack]
    #22269964 - 09/21/15 03:12 PM (8 years, 4 months ago)

Actually that doesn't make sense as the density is for diamond and I didn't consider bond lengths.  I'd have to see more information to help you.  Carbon isn't a molecule it is an element, and you aren't dealing with unbonded carbon.  I might have made a mistake by 1 magnitude somewhere.


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Re: chemistry help [Re: fapjack]
    #22270050 - 09/21/15 03:29 PM (8 years, 4 months ago)

I honestly don't even know what your looking for in the question. When solving any standard problem you are going to be dealing with Carbon 12 so you don't need to worry about isotopes and you don't include forces because that would be getting into physical chemistry which is a whole different ball park. I don't get what you mean by saying you are trying to find Avogadro's number? It's always the same.


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Invisiblemicro
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Re: chemistry help [Re: Gorlax]
    #22270087 - 09/21/15 03:37 PM (8 years, 4 months ago)

I think they are just asking to solve for Avagadro's number to test the margin of error but in this case I don't see how you can get that without a lot of data that is either not there or they probably aren't trying to ask (like p chem).


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Invisiblemicro
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Re: chemistry help [Re: micro]
    #22270383 - 09/21/15 04:55 PM (8 years, 4 months ago)

Sorry, let me correct myself...

There *is* a way, just find the normality of the solution; you have density so you can find it that way.

That has nothing to do with a carbon atom's radius though.


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