November 27, 2015

Homework Help: Chemistry

Posted by Rob on Friday, January 11, 2013 at 2:50pm.

I have this question which I believe I solved correctly, but I was wondering if someone could look it over to make sure?

The question is...

Assay for Vitamin A (a fat soluble vitamin) required an extraction step into ether. In this assay, 2.00 mL of serum are extracted into 5.00 mL of ether. The extraction step is 100% efficient. Ether and serum are immiscible. The ether layer is separated and taken to dryness. The remaining residue is the resuspended in 10 mL of methanol. The concentration in this final solution is 10 ng/mL. What is the concentration of the Vitamin A in serum using units of Moles/liter? (Vitamin A M.W. = 450)

My solution:

10ng Vitamin A/10mL * 1g/1x10^9ng * 1000mL/1L * 1mol/450g Vitamin A

= 10,000 mol/4.5x10^12L

= 2.22x10^-9 mol/L

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