Chapter 7.7, Problem 19P

To determine

To Find: Amount of water evaporated from solution

Answer to Problem 19P

  $8l$

Explanation of Solution

Given:

  $\begin{array}{l}\text{Solution: }20l\\ \text{Salt solution before evaporation: }30\%\\ \text{Salt solution after evaporation: }50\%\end{array}$

Formula Used:

  $\text{Total amount }\times \text{ \% content = Amount}$

Calculation:

  $\begin{array}{l}\text{Let the amount of water evaporated from solution be : }x\\ \text{Original composition of salt in solution: }20\times 0.3=6\\ \text{evaporated composition of salt in solution: }x\times 0=0\\ \text{New composition : }\left(20-x\right)\times 0.50=0.5\left(20-x\right)\\ \Rightarrow 6=0.5\left(20-x\right)\left(\because \text{ Composition of salt remains constant in both cases}\right)\\ \Rightarrow 6=10-0.5x\\ \Rightarrow -4=-0.5x\\ \Rightarrow x=8l\\ \end{array}$

Conclusion:

Thus the amount of water evaporated from the solution is: $8l$