[Lo.Lee.Ta.]

Hhhh... Cannot figure this out. #=_=

Given α° for menthol= -50°
Given α° for neomenthol = +16°

The observed rotation for the product mixture in lab was: -3.9
The concentration of polarimetry solution: .253g/mL

α° = α/(l*c)

α° = -3.9/(1*.253)

α° = -15.42


...The manual says, "the product ratios in decimal form can be determined from the following equation:

100*(α°product mixture) = x(α°menthol) + (100 - x)(α°neomenthol)"

100*(-15.42) = x(-50) + (100 - x)(16)
-3141 = -66x
x = 47.6

This value of x is not in decimal form like they said it would be...
Someone on Yahoo Answers said something like the x value you get (x100) is the percentage of the (-) or Levorotary molecule.
And the percentage of the (+) or Dextrorotary molecule is found by (100% - levorotary %).

I'm not even sure if what they said was right, and I cannot find an example worked anywhere! D:

...I do not have the x in decimal form. What am I doing wrong?

Please *delete me*
Thank you so much!

[Borek]

...The manual says, "the product ratios in decimal form can be determined from the following equation:

100*(α°product mixture) = x(α°menthol) + (100 - x)(α°neomenthol)"

These are percentages, and the manual is lousy. Note that if you divide both sides by 100 (which is a conversion factor for %) you will get

[tex]\alpha^0 = \frac x {100} \alpha^0_{menthol} + (1 - \frac x {100}) \alpha^0_{neomenthol}[/tex]

and now x/100 is a decimal fraction as expected.

Basically you have two equations in two unknowns - one describes total concentration as a sum of concentrations, other describes the rotation as sum of rotations. Equation given in the manual has one unknown already eliminated and is mangled by conversion to percentages - just to confuse you.