Doctor's Cocktail
After Ripley crash-landed on Fiorina 161, she needed medical attention. In one scene we see the doctor preparing to
give her an injection. It is a mixture of drugs. For
the purposes of keeping the problem simple, we will change
this to just one drug dissolved in water.
Assume that a person needs 3.5 x 10-4 moles of the
the drug per kilogram of body weight.
Assume that Ripley weighs 120 lbs.
Use the 2.2 lb kg-1 conversion factor to take pounds
to kilograms.
-4
1 kg 3.5 x 10 mols L 1000 mL 1 cc
120 lbs x ------- x --------------- x ------- x ------- x ---- = 38.1 cc
2.2 lbs kg 0.5 mol 1 L 1 mL
At this point we should realize we have a problem. We can't
pump 38.1 cc's into a person. We need to increase the
concentration so that the total volume is less than 5 cc.
A typical needle can inject up to 5 cc.
New goal: Calculate the concentration that will allow a
4 ml injection to administer the proper amount of the
drug.
-4
1 kg 3.5 x 10 mols
120 lbs x ------- x --------------- = 0.019 moles
2.2 lbs kg
We need 0.019 moles of the drug for Ripley. Given a number
of moles, and a volume (we said we wanted to use 2 cc's),
we can calculate the concentration:
0.019 moles 1 cc 1000 ml
---------- x ---- x ------- = 4.8 mols L-1 or 4.8 M
4 cc 1 mL L
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Last Revised 02/25/98.
Copyright ©1998 by William L. Dechent. All rights reserved.