How many grams of K3PO4 (Mm=212 g/mol) must be added to 655 g of water to make a solution with a colligative molality of 0.165 m?




(x/212)/.655=.165 would give me 22.9119 grams which makes sense and should be right but isn't.

1/26/2009 9:45:57 PM

o wait

nvm

i get 22.9119 as well

try 22.9 (significant digits)

1/26/2009 9:49:45 PM

chemistry is something that will never, ever make any sense to me.

1/26/2009 9:50:25 PM

^^same thing (x/212) = moles of K3PO4

gives me 22.9119 which supposively isn't the answer

1/26/2009 9:51:28 PM

I hated chemistry

both in high school, and in college

1/26/2009 9:52:03 PM

yeah, i just realized that

try 22.9, the least # of significant digits given in the problem is 3, so your answer should be to 3 sig digits

1/26/2009 9:52:08 PM

^doesn't really matter here, but i tried it anyway shit isn't working

1/26/2009 9:52:31 PM

Quote :

"supposively"

is that a mixture of positive and supposedly?

1/26/2009 9:52:44 PM

^ chrome says it's a word.

1/26/2009 9:55:02 PM

oh lawd, how did i miss this

colligative molality

multiply the molality you got by the van't hoff factor of potassium phosphate

i believe it should be near 4 in a neutral solution but might be higher based on the extent of the hydrolization of the phosphate ions

1/26/2009 9:56:42 PM

It's supposedly, n00b.

1/26/2009 9:57:02 PM

don''t listen to evan

first, he'll start with offering helpful advice in this thread

you still won't get the right answer, so then evan will say "I need to see the problem right in front of me. Come on over my place, and we'll work on it together"

Next thing you know, he's be trying to put your dong in his mouth

1/26/2009 9:59:49 PM

isn't that how all tutoring sessions go down?

1/26/2009 10:00:49 PM

Colligative brorape-ality?

1/26/2009 10:01:59 PM

van't hoff was all about some brorape, son

1/26/2009 10:02:32 PM

5.727

1/26/2009 10:02:34 PM

Quote :

"multiply the molality you got by the van't hoff factor of potassium phosphate i believe it should be near 4 in a neutral solution but might be higher based on the extent of the hydrolization of the phosphate ions"

thank you, divided the final answer by 4 to account for it and got it right. wtf is this colligative shit?

1/26/2009 10:03:12 PM

Colligative properties are properties of solutions that depend on the number of particles in a given volume of solvent and not on the mass of the particles. (so K3PO4 is 4 particles, not just one)

Colligative properties include: lowering of vapor pressure; elevation of boiling point; depression of freezing point; osmotic pressure.

1/26/2009 10:05:21 PM

^beat me to it

1/26/2009 10:05:45 PM

people answered already

yea caught that after the fact

V..Gen chem makes me feel fucking retarded and I majored in chem

[Edited on January 26, 2009 at 10:11 PM. Reason : maor]

1/26/2009 10:06:49 PM

no, he's doing the calculations right. molality = mol solute/kg solvent, molarity = mol solute/l of solution. colligative molality is just molality multiplied by the van't hoff factor of the solute

1/26/2009 10:08:27 PM

This thread makes me miss Chem 101

1/26/2009 10:10:41 PM

we didn't do this colligative shit in AP Chem. andd i had to look for it in the 201 text for a while just to find it. thank you tdub

1/26/2009 10:12:08 PM

Who do you have?

1/26/2009 10:13:22 PM

warren

1/26/2009 10:13:36 PM

I feel bad for you son.

1/26/2009 10:17:20 PM

I had Dr. Tucker. I think he gave me an A just because he felt sorry for me.

1/26/2009 10:18:02 PM

fucking chemistry

it's a nice thing to have when you're fucking.

1/26/2009 10:18:51 PM

^an A in CH 201 would greatly help my GPA right now, if only Warren would hand me one

1/26/2009 10:18:53 PM

I had Warren, I got a B. Chem 201 ain't shit.

1/26/2009 10:22:49 PM

other than this colligative shit it's been a cake walk so far

1/26/2009 10:23:51 PM

we did collgative stuff in chem today. Dr. banks isn't to bad

1/26/2009 11:08:56 PM

colligative properties aren't that bad once you understand why they work the way they do, then it just makes sense

p.s. why are you taking ch201 if you took ap chem?

1/27/2009 3:02:04 AM

oh chemistry, how I miss art though.

1/27/2009 3:17:19 AM

More like

mololity, amirite?

1/27/2009 4:33:47 AM

More like

mololity, amirite?

1/27/2009 4:33:47 AM

Quote :

"why are you taking ch201 if you took ap chem?"

it placed me out of 101 and 102 but i need 201 and 202 for my major as well as 101 and 102.

1/27/2009 10:35:26 AM

he didn't get a 5 (though i dunno if ncsu does the 3-4 = 101/102 and 5 = 101/102/201/202 probably not)

chem 201 is the same as 101 but more detailed....

1/27/2009 11:14:58 AM

I might can help you....I took ch 101 3 times.

1/27/2009 11:17:03 AM

I think I got out of 101, 102, 201 and 202 with a 4 on the AP. Though part of it might've been chem credits from NCSSM.

1/27/2009 11:20:03 AM

there's no cookie

1/27/2009 12:30:16 PM

I majored in English and History.

Hello, thread.

1/27/2009 12:31:40 PM

Quote :

"he didn't get a 5 (though i dunno if ncsu does the 3-4 = 101/102 and 5 = 101/102/201/202 probably not)"

I was focused on well... womens in my class during thermo and electro chem, and i kicked the multiple choice of that test's ass but thermo and electro were big on the open section that year and i got a 3 (one of 3 passing scores in my class)

1/27/2009 12:33:56 PM

lol better than I did, i didn't even take ap chem.

1/27/2009 12:46:46 PM

shit was SO TUFF when i paid attention.

1/27/2009 12:48:09 PM

1/27/2009 12:49:41 PM

lol wut

1/27/2009 12:54:50 PM