# Dilution Problem

• Aug 3rd 2012, 05:19 AM
djrx
Dilution Problem

Question is:
If 0.5 mL of a mumps virus vaccine contains 5000 units of antigen, how many units would be present in each milliliter if the 0.5 mL of vaccine was diluted to 2 mL with water for injection?

I tried setting up like this. [0.5][5000] = [2][x]. = 1250 units
• Aug 3rd 2012, 06:11 AM
emakarov
Re: Dilution Problem
How many units of antigen are there before dilution? After dilution? What is volume of the diluted solution? What is the number of units per mL after dilution?
• Aug 3rd 2012, 06:20 AM
djrx
Re: Dilution Problem
Thanks. The question is copied verbatim from the textbook.
• Aug 3rd 2012, 06:23 AM
emakarov
Re: Dilution Problem
Quote:

Originally Posted by djrx
The question is copied verbatim from the textbook.

Does this mean that you now know how to answer it?
• Aug 3rd 2012, 07:47 AM
djrx
Re: Dilution Problem
I don't understand what u are asking. I showed how I setup my calculation above with the result of 1250. There should be the same # of units in the solution before and after diluting right? 5000. The volume of diluted solution is 2mL
• Aug 3rd 2012, 08:32 AM
GJA
Re: Dilution Problem
Hi, djrx.

If I am understanding the problem correctly (which may not be the case), I think the answer should be 2500 units. If there are 5000 units in .5mL before dilution, then there will be 5000 units in the 2mL after dilution (since the water doesn't contain any antigen). That means that in 1mL of the solution there should be 2500 units. Is this what your book has?

If I am not understanding or have made an error let me know. Good luck!
• Aug 3rd 2012, 11:14 AM
djrx
Re: Dilution Problem
Yes, 2500 units is correct. It does make sense the way you solved it. How would you go about setting this up using proportion/ratio? The question is from a chapter on ratios/proportion and i was stuck trying to fit it in a formula. Thank you all for your time.
• Aug 3rd 2012, 11:47 AM
GJA
Re: Dilution Problem
If you want to set up an equation like you did in your first post, you were on the right track initially. Take x=number of units in 1mL of solution. That means 2x represents the number of units in 2 mL of solution. As reasoned out in the previous post, we should have 5000 units of antigen in the 2mL of solution. Since 2x is the number of units in 2mL of solution and so is 5000, we get the equality

5000=2x,

which it looks like you know how to solve.

In the first post 2500 was on the left hand side (written as (.5)(5000)). Is this what you were looking for?