Question

How many liters of pure water should be mixed with a 19-L solution of 80% acid to produce a mixture that is 90% water? What's the amount of pure water in liters?

A) 3 liters
B) 4 liters
C) 5 liters
D) 6 liters

Answer 1

To produce a mixture that is 90% water, 35 liters of pure water should be mixed with a 19-L solution of 80% acid.

Step-by-step explanation:

To find the amount of pure water needed, we can set up an equation using the concept of the amount of acid in the solution before and after the addition of water. Let's assume the amount of pure water needed is x liters.

Before mixing, the 19-L solution contains 80% acid, which means it contains 19 * 0.8 = 15.2 liters of acid.

After mixing, the mixture is 90% water, so the amount of acid in the mixture is 10% of the total volume. This means 0.1 * (19 + x) = 15.2.

Simplifying the equation, we get 1.9 + 0.1x = 15.2, and solving for x gives x = 35 liters.

Therefore, the amount of pure water needed is 35 liters, which means option D is the correct answer.