Final answer:
To obtain a mixture of 156 liters containing 35% acid, the chemist should use 78 liters of the 25% acid solution, 156 liters of the 45% acid solution, and 78 liters of the 75% acid solution.
Step-by-step explanation:
To solve this problem, we can set up a system of equations representing the amounts of each acid solution used in the mixture.
Let's say the amount of the first acid solution used is x liters.
The amount of the second acid solution used would be 2x liters since we are using twice as much of the 75% solution as the 45% solution.
Therefore, the amount of the third acid solution used would be 156 - x - 2x = 156 - 3x liters.
We can now set up an equation using the percentages of acid in each solution:
(0.25x + 0.45(2x) + 0.75(156 - 3x)) / 156 = 0.35
Simplifying the equation and solving for x, we can determine the amount of each solution:
x = 78 liters of the 25% acid solution
2x = 156 liters of the 45% acid solution
156 - 3x = 78 liters of the 75% acid solution