If I have a 12% solution of hydrogen peroxide (2 cups) and dilute it with 1 cup water, what is the new percentage?

Question

I'm actually doing a lab, this isn't a textbook problem (college bio)

Answer 1

Well in your 2 cups you have 0.12 x 2 cups of hydrogen peroxide (so 0.24 cups) and 2 - 0.24 = 1.76 cups of water

So if you add 1 cup of water you have 0.24 cups of hydrogen peroxide and 2.76 cups of water

So the new percentage is (0.24 / (0.24 + 2.76)) x 100 = 8 %

Answer 2

To provide an alternate solution to @Mike D.'s answer, in chemistry it is a general practice to use the formula V1C1 = V2C2 where...

V1 = initial volume = 2 cups

C1 = initial concentration = 12%

V2 = final volume = 3 cups (2 cups + 1 cup)

C2 = final concentration = ?

(2 cups)(12%) = (3 cups)(x%)

x = (2)(12)/3

x = 8%