Prepare a lotion using Aristocort 1% to be mixed with 60 mL of hand lotion to make a 0.5% lotion. What is the weight of Aristocort 1% in the prepared lotion?

Question

1% is 1 part of solute in 100 parts of total solution.

Answer 1

Hi Alex:

 

I take it that you do NOT want the weight but the volume in your question.

 

Let A be the volume of the Aristocort 1% (1% = 0.01) lotion.  We know that the volume of the hand lotion (which has 0% of Aristocort) is 60 mL.  The total solution has a strength of 0.5%, (0.5% = 0.005) and the volume of the total solution is (A+60) mL. Thus

 

A(0.01) + 60 (0) = (A+60)(0.005)

 

0.01 A = 0.005 A + 0.3

 

(0.01 - 0.005) A = 0.3

 

0.005 A = 0.3

 

A = 0.3 / 0.005 = 60.

 

This answer is kind of obvious.  You have to reduce the strength of the Aristocort solution in half, from 1% to 0.5%. You have 60 mL of hand lotion which has NO Aristocort. Then you must add to it an equal amount of Aristocort 1% solution. Then the strength of the total solution (120 mL) is one_half of what you had before.  Get it?

 

Dr. G.

Answer 2

if you take 60 ml of Aristocort 1% and mix it with 60 ml hand lotion, the new strength of the lotion would be half the original or .5%.

 

We would need a weight for the compound per volume to answer the question.