Question

Which substance will most affect the freezing point of water if 1 mole of the substance is added to 1 kilogram of water?



PbS


C8H18


Na3PO4


NaCl

Answer 1

The substance that will affect the freezing point of water will be able to break into ions

Answer 2

dT=iKfm
Where T is the change in temperature
Kf is a constant
m is the molality
i is the van't Hoff dissociation number

To find m we have one mole of solute per 1 kg of solvent so m=1
Kf is a constant
The only thing effecting the change in temperature is i

For example CaCl2 --> Ca2+ + 2Cl-
i in this case equals 3
So you want the one with the biggest i

Answer 3

Sorry about the wait I ended up getting logged out for some reason

Answer 4

What do you mean the biggest i?

Answer 5

The biggest number of ions that the compound splits into.

Answer 6

Well I don't understand chemistry at all I'm horrible at it. Can I possibly just have the answer please?

Answer 7

No, that is against OS policy and is not conducive for learning. Do you know the difference between ionic and covalent compounds?

Answer 8

CaCl2 dissociates into Ca and 2Cl so i = 3
We can do this with the 4 options

Answer 9

No I don't and people post the answer on OS all the time and it hasn't been a problem. I need to pass this online course so I can go to trade school so it would be great if someone could help me @JoannaBlackwelder

Answer 10

Both @JoannaBlackwelder and I are happy to help but we would like to make sure that you understand why it is the answer too

Answer 11

I'm not really too worried about understanding it to be honest. I'm not going to do anything in my life with chemistry ever. I just need to complete a course so I can move onto Biology at my new school. I just need to know which one is the right answer.

Answer 12

That is called cheating, not help and I wont cheat for you.

Answer 13

Cool then you don't have to respond to my stuff.

Answer 14

The thing is though is I'm a chemistry major so I enjoy explaining the one thing that I want to do for the rest of my life. I don't know about Joanna but I know she enjoys chemistry as well and enjoys explaining it

Now if you look back at the question we want to look at this dissociation factor
PbS doesnt dissociate in water
C8H18 doesn't dissociate in water
Na3PO4 dissociates into 3Na+ and PO4-
NaCl dissociates into Na+ and Cl-

Answer 15

Since Pb is a metal, and S is a nonmetal, PbS is an ionic compound and would also dissociate into ions. Are you getting something else, @taramgrant0543664 ?

Answer 16

I questioned it too @JoannaBlackwelder i looked it up and it said it wasn't soluble in water but I didn't really trust that source but i didn't find anything contradictory but either way the compound isn't the answer

Answer 17

Good call. :-)