Question 570788: I am stuck on this math word problem.
It states: you need to make a 600mL solution of hydrogen peroxide. You find a bottle of 80mL of 30% hydrogen peroxide. How much mL of 30% hydrogen peroxide would you add to how many mL of water to make exactly 600mL of hydrogen peroxide?
I would greatly appreciate any help!
Thanks
Answer by KMST(5328)   (Show Source):
You can put this solution on YOUR website! You left out some information. You need to make a solution of hydrogen peroxide, but you left out the concentration you need. I'll pretend you need a 4% solution.
In analytical chemistry we base dilutions calculations on the fact that the amount of the substance we are diluting is the same before and after adding water (or other solvent), so we say that volume times concentration (equal or proportional to amount of substance in some unit) is the same before and after diluting.
You will need x mL of the 30% peroxide solution to make 600 mL of 4% solution
(600 mL)(4%)=(30%)(x mL)
dividing both sides by 30%
(600 mL)(4%)/(30%)= x mL
x mL = 80 mL
So for 600 mL of 4% solution you would use the entire 80 mL of 30% solution you have, and would add water to make the volume up to 600 mL.
You would need 600 mL - 80 mL = 520 mL water.
NOTE: The 30% peroxide solution is about the most concentrated hydrogen peroxide solution you can get (although once I got a 35% solution in the lab). It burns skin (it turn white and itch-burns badly), and discolors many materials. Do not try this at home.
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