Question 317379
Start by finding the amount of acid that would be in the 4 liter solution you end with. So that would be 10% of 4 liters, or .4 liters. So that .4 liters of acid has to all come from the solution of half acid and half water. So .4L of acid = 50% of the total amount of mixed solution, which means that there will be .8 solutions of that solution. If .8 liters of the final 4 liter solution is made up of the half acid half water solution, then the final 4 - .8 = 3.2 liters is pure water.