Chapter A.8, Problem 42AYU

To determine

To find: How much water must be evaporated?

Answer to Problem 42AYU

Evaporate 96 ounces of water.

Explanation of Solution

Given:

How much water must be evaporated from 240 gallons of a $3\%$ salt solution to produce a $5\%$ salt solution?

Calculation:

Let $x=$ amount of water that must evaporate.

Now we know that the amount of pure salt in the original solution $\left(0.03\right)\left(240\right)$ has equal the amount of pure salt in the final solution after evaporation has taken place $\left(0.05\left(240-x\right)\right)$.

So, $\left(0.03\right)\left(240\right)=\left(0.05\left(240-x\right)\right)$

$7.2=12-0.05x$

$-4.8=-0.05x$

$x=96$

Therefore evaporate 96 ounces of water.