How much water must be evaporated from 17 qt of a 70% antifreeze solution to produce an 85% solution?

Question

Answer must be given in quarts

Answer 1

The best way to address this problem is to compare the amount of pure anti-freeze at the beginning and end states.

 

Since water is being evaporated, for this problem the amount of pure antifreeze is the same at the beginning and the end.

 

at beginning

 

17qt * 70% = 11.9qt pure anti-freeze.

 

at end this antifreeze must be 85% of the final volume

 

V * 0.85 = 11.9qt   V= 11.9/.85 = 14qt.    

 

Starting volume was 17 qts so 3 qts of water was evaporated.