have a 700ml solution of 30% acid, needs a 50% solution of acid. How many ml of 100% acid should be added?

8 years agohmmm ok. so we're saying that the entire solution needs to be .5 (50%)

8 years agoso you can solve an equation like this: (.3*700 + 1*x)/(x+700) = .5

8 years agoso multiplying both sides by x+700, we get : .5x + 350 = x + 210

8 years agosubtract .5 from both sides, and you get .5x + 210 = 350

8 years agoso .5x = 140

8 years ago140/.5 = x = 280

8 years agoso I'd say 280ml

8 years agobasically - .5 is the entire fraction of acid in the total solution, hence my equation in the first step - so we know the first part of the end solution since it's given

8 years ago700ml * .3 is pure acid

8 years agowhat you add to the solution, is also pure 100% acid, so 1*x

8 years agothe denominator in this case will be the total amount of solution (so the original 700ml plus whatever you added)

8 years agoand we know that the entire thing - the fraction - is .5

8 years agoand following that logic the answer is 280ml

8 years agoi.e. .5 = total ml acid / total ml solution (after you've added everything)

8 years agogood luck!

8 years agoThank you

8 years ago