A biologist is testing the effects of acid rain on plant growth. She has 500 mL of a 12% acid solution, dut wants to use a 7% solution. To the nearest mL, how much water should she add to obtain the desired concentration?:eek:

If 500ml equals 12%, then I am assuming that 41.6ml is equal to 1%.

To get down to 7% acidity, just multiply 41.6ml by the number of percent reduction needed i.e 5.

Answer is 208ml - I think.