Question

Vitamin K is involved in normal blood clotting. When 1.56 g of vitamin K is dissolved in 25.0 g of camphor, the freezing point of the solution is lowered by 5.23 °C. . Calculate the molar mass of vitamin K.

I posted this yesterday but I got the wrong answer and could use some step by step help?

Thanks

Answer 1

I think I answered your question. The easy way to find the error is for you to post your work and let me check it. I'm happy to do that for you.

Answer 2

when Im getting my Kf do i change it from Celsius to Kelvin before i do my calculation?

Answer 3

You can but it doesn't matter. I think Kf for camphor is about 38 C/m (37.7 maybe?) or something like that.

Answer 4

What I meant was that Kf for camphor is 37.7 celsius/m or 37.7 Kelvin/m

Answer 5

Im sure i did this wrong but this is what i did

deltaT=Kfm
m=mols solute/ kg solvent

1.56g vitamin k/83.8g= 0.019

m=0.019/ 0.025 = 0.76

Answer 6

delta T=Kfm

-5.23=37.8m
-5.23-37.8 =m
m=-43.03

Answer 7

I think I wrote this:
delta T = Kf*m
Substitute and solve for m = molality

m = mols solute/kg solvent
Substitute and solve for mols solute.

mols = grams/molar mass
Substitute and solve for molar mass.
<b>I don't think you followed the steps.</b>

Take it one step at a time.
delta T = K*m
5.23 = 37.7*m
m = 5.23/37.7 = about 0.138m

Next.
m = mols solute/kg solvent
0.138 = mols solute/0.025
mols solute = 0.138 x 0.025 = about 0.00346 mols

Next:
mol = grams/molar mass
0.00346 mols = 1.56g/molar mass
molar mass = ?

Answer 8

nope. That isn't the way math works.

Answer 9

so i do 0.00346mols x 1.56 = 0.00539?

Answer 10

no.
0.00346 mols = 1.56g/molar mass
molar mass = 1.56/0.00346 =?

Answer 11

I see I spelled anonymous wrong.

Answer 12

Thanks so so much! I was really confusing myself! The steps really helped!