Posted by ANNA on .
A chemist has 12.0 M HBr and would like to use it to make 500.0 mL of 3.5 M HBr. describe how she should do this

chemistry 
DrBob222,
mL x M = mL x M
mL x 12.0 = 500 x 3.5
mL = you can do itabout 60 mL or so.
The reason I worked it through is to show you what NOT to do. You DON'T use 60 mL of the concd soln (or whatever the number turns out to be) and add 500 mL of water. Instead, you take 60 (or whatever) and add to water to make a total of 500 mL of solution. On an exam, that is the tricky part. The prof will want to see that you have written that the total solution is 600 mL, not 60 mL added to 540 mL because volumes are not additive and in accurate work you may not assume they are. 
chemistry 
Josh,
1.5 x 10(10) mL