Question

A scientist has a 100 liter cistern filled with pure acid.with a 20 liter jug he remove precisely 20 litres from the cistern, replacing it with water. He repeats this process again.What is the concentration of acid left in the cistern? After how many such processes will the concentration drop below 50%?​

Answer 1

The concentration of acid left in the cistern decreases with each process of dilution with water. After 5 processes, the concentration will drop below 50%.

Step-by-step explanation:

To find the concentration of acid left in the cistern after each process, we need to consider the dilution that occurs when water is added.

Let's start with the initial concentration of the acid in the cistern, which is 100% or 1 M. After the first process, the cistern contains 80 liters of acid and 20 liters of water. The concentration of the acid is now 80/100, or 80%.

After the second process, the cistern contains 64 liters of acid and 36 liters of water. The concentration of the acid is now 64/100, or 64%.

We can continue this pattern and find that after the fifth process, the concentration of the acid will drop below 50%. Therefore, it will take 5 processes for the concentration to drop below 50%.