Question

How many millimeters of water would you add to 75 mL of a 15% acid solution to make a 10% acid solution?

Answer 1

50 more needs to be added.

Answer 2

Thanks for the help @Ellews

Answer 3

I don't agree. The amount of acid remains the same in the two solutions, so\[.15(75)=.10(75 + x)\]

Answer 4

Then what would you say is the correct answer? @NoelGreco

Answer 5

37.5 ;)

Answer 6

no but seriously he has a point

Answer 7

i forgot to consider the fact that the amount of acid does not change. so .15(75ml)=.10(75+x) the amount of extra would be 37.5mL :) thanks @NoelGreco

Answer 8

Alright so thank you both, @Ellews and @NoelGreco

Answer 9

But just a question, what would the equation look like if you reverse the whole problem into knowing the amount of acid added but not the original percentage?

Answer 10

15 percent of 75 =11.25
so "11.25 ml of acid"

Answer 11

If 3 qt of antifreeze are added to 9 qt of a 40% antifreeze solution, what is the concentration of antifreeze in the new solution? There, an example problem. How would the equation look like for this problem?

Answer 12

I do these mixing problems this way



The amount of antifreeze has to be the same on both sides.

Answer 13

So x is the concentration of antifreeze in the new solution?

Answer 14

Yes. In these problems water is most often the solvent. You'll never be asked, "What's the concentration of water?"

You must follow the solute (acid, antifreeze) and make your equation.