



 
Hi Shanah. If you want 360mL of solution which is 75% acetic acid, then how many mL of it is pure acetic acid? Answer: 75% x 360mL. Let's call this quantity A. So that's how much acetic acid you need. Your stock is 99% acetic acid, so to get A mL of acetic acid, you need 99% x S = A where S is the volume of the stock acid. We can rewrite this as S = A / 99%. Substituting in the expression for A into this, we get:
which gives the number of mL of stock acid to pour. Then just top it up to the 360mL level with distilled water: W = 360mL  S. Hope this helps,  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 