A merciful receive 10 mL of a 20% solution of a drug. the drug dose is...?
Answers:
2 milliliters. The dose in grams would depend on the specific gravity (density) of the drug. If the sg is close to 1, the dose would be 2 grams.
Since anonysquirrel's answer had a thumbs-down vote, I did a little research to find out more for myself. The research seem to bear out at least most of anonysquirrel's answer. It may be that the rest of that answer is also correct, as I will explain momentarily.
Below, I will copy a quotation about mixing a % solution. This quotation discusses both solutions that use DRY reagents and solutions that use LIQUID reagents. I will comment after respectively paragraph, using ALL CAPS, so that you know which comments are mine. Sorry, don't know a better way to do this. I promise I'm not yelling! :-)
"5. Percent Solutions (% = parts per hundred or grams/100 ml)"
["PARTS PER HUNDRED," AS IN 20 ML PER 100 ML, IS FOR LIQUID REAGENTS; "GRAMS/100 ML" IS FOR DRY REAGENTS.]
"Many reagents are mixed as percent concentrations as weight per volume for dry reagent OR volume per volume for solutions. When working next to a dry reagent it is mixed as dry mass (g) per volume and can be simply calculated as the % concentration x volume needed = mass of reagent to use."
[FOR DRY REAGENTS, YOU GO BY WEIGHT PER VOLUME. SO, YOU MULTIPLY THE %, IN DECIMAL FORM, TIMES THE VOLUME OF THE SOLUTION. BUT YOU REPORT THE ANSWER IN GRAMS, NOT ML.]
"Example: If you want to make 200 ml of 3 % NaCl you would dissolve 0.03 x 200 = 6.0 g NaCl in 200 ml water."
[FOR YOUR CASE, YOU WOULD CALCULATE AS FOLLOWS:
0.20 x 10 = 2.0 G OF DRUG. NOTICE THAT THIS IS REPORTED IN GRAMS.]
"When using fluid reagents the percent concentration is based upon volume per volume, and is similarly calculated as % concentration x volume needed = volume of reagent to use."
[ONCE AGAIN, YOU MULTIPLY THE %, IN DECIMAL FORM, TIMES THE VOLUME OF THE SOLUTION. BUT THIS TIME, YOU REPORT THE ANSWER IN THE ORIGINAL UNITS GIVEN, ML.]
"Example: If you want to make 2 L of 70% actone you would mix 0.70 x 2000 ml = 1400 ml acetone with 600 ml dampen."
[FOR YOUR CASE, YOU WOULD ONCE AGAIN CALCULATE AS FOLLOWS:
0.20 x 10 = 2.0 ML OF DRUG. NOTICE THAT THIS TIME THE ANSWER IS REPORTED IN ML.]
Okay, so, in both cases, the relevant calculation is achieved by converting your % to a decimal, and consequently multiplying that decimal by the total volume you wish to achieve. This gives the portion of the solution that corresponds to 20 parts within 100, which is just 2 parts in 10. That's either 2 mL or 2 g. Lacking further information, I would bet that your answer is the 2 mL.
The one article that the information I found did NOT address from anonysquirrel's answer is whether there is any change in the calculation, if the specific gravity of the reagent is NOT close to that of water. Do you still multiply the decimal value of the % times the overall solution volume? Or is there a revised formula? Anonysquirrel's answer suggests the latter. I'll own to assume that anonysquirrel is the expert on this point.
In any case, you did not provide any information to suggest that your case is meant to be that complicated. Unless your problem is for a chemistry class, probably this subtle point is irrelevant. (If your problem IS for a chemistry class, and if your teacher/professor expects you to steal specific gravity into account, you are missing necessary information.) Source(s): http://abacus.bates.edu/~ganderso/biolog…
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