Question

Can anyone help with this question!

Answer 1

Question:

Answer 2

if dont have the formulas in your notes, just dimensional analysis to match the units

Answer 3

I have the formula but not sure how to complete part C, D or F

Answer 4

Would you be able to show me how to do it?

Answer 5

for C) you're just diluting the initial concentration by half, so instead of 0.13 M you have 0.65 M, D) is the same thing as A)

For F) find the rotation of each enantiomer separately, then subtract the rotation of one from the other (from the concentrations, you can see that the D enantiomer will cause more optical effects)

Answer 6

post what you have, i'll help you get it right

Answer 7

I cant check if they are right till I fill in all of the blanks

Answer 8

is the volume in the cuvette 10 mL?

Answer 9

cuz i know the path length is 1 dm = 10 cm

Answer 10

If you don't mind me asking what level of chemistry is this?

Answer 11

First semester of organic chemistry

Answer 12

I think the volume is about 2 ml for a cuvette.

Answer 13

is that the volume you're using to solve these?

Answer 14

I was just converting from M and moles to liters. M= mol/L

Answer 15

Once I found liters, I plugged the numbers into the equation. Thats how I did the first part.

Answer 16

This is what I did:
119/0.130

Answer 17

Moles over M

Answer 18

oh right lol so then you just multiplied by the 0.16 degrees?

so i think without doing any calculations, for C) is half of the initial rotation, 0.16/2= 0.08 degrees (because half of the amount)

for D) it would be half of what you got in A)

Answer 19

How do you do part F?

Answer 20

I think the point
A)
specific rotation = observed rotation / (c*l)
l = cell path length in decimeters. (1 decimeter = 1 dm = 10 cm. A standard polarimeter tube is 1.00 dm in length.)
c = concentration in g ml-1 for a pure liquid compound (i.e., the liquid's density), or g 100 ml-1 for a solution.
specific rotation = 0.16 deg / c 1

c= 0.130 mol x (119 g/ mol) /1000 mL =0.01547 g/mL
specific rotation = 0.16 deg /(0.01547 g/mL x 1 dm) = 10.34 deg mL/g dm

B) is correct
C) @aaronq said is going to be 1/2 of 0.16 = 0.08
D) I think that the specific rotation of a solution is independent of the concentration and is a intensive property of the solution dependent of the nature of the solute and the solvent. Then I think will be the same that A.
The observed rotation is dependent of the concentration.
E) the specific rotation will have the same numeric value but different sign that A because is the other enantiomer

F) the observed rotation you have to subtract
0.01 moleD - 0.005 mol L = 0.005 mol D x 119 g/mol = 0.595 g
this is in 100ml

observed rotation = specific rotation x concentration x 1 dm
observed rotation = 10.34 deg mL/g dm x (0.595 g/100mL mol)
observed rotation = 0.06 deg

Answer 21

http://www.chem.ucla.edu/harding/tutorials/stereochem/calcs.html