Chapter 9, Problem 11MPS

To determine

To Find: The quantity of water to be evaporated.

Answer to Problem 11MPS

  $3$ kg

Explanation of Solution

Given: How many kilograms of water must be evaporated from $8kg$ of a $25\%$ salt solution to produce a $40\%$ salt solution.

Let $x$ be the quantity of water to be evaporated

Then

  $8kg$ of a $25\%$ salt solution

i.e.

  $\begin{array}{l}8\times 25\%\\ 8\times 0.25=2kg\end{array}$

i.e.

  $2kg$ of salt solution

Then

Water to be evaporated is

  $\begin{array}{l}\frac{2}{8-x}=40\%\\ \frac{2}{8-x}=0.40\\ 0.40(8-x)=2\\ 3.2-0.4x=2\\ x=3\end{array}$

Hence, $3$ kg of water must be evaporated.