How much of a 50% acid solution should be mixed with 10 liters of an 20% acid solution to end up with a 30% acid solution?

Do your own homework.

Concentration multiplied by volume gives you the number of moles in a solution.

Number of moles in 1 + Number of moles in 2 = Total number of moles.



C1 is 0.5, C2 is 0.2, V1 is what you're looking for, V2 is 10, C is 0.3, V is V1 + V2

I think this should be easy enough, don't you think? :)