Question

A geochemist measures the concentration of salt dissolved in Lake Parsons, an isolated salt lake. He finds a concentration of 21.·gL−1. The geochemist also measures the concentration of salt in several nearby non-isolated lakes, and finds an average concentration of 6.67·gL−1. Assuming the salt concentration in Lake Parsons before it became isolated was equal to the average salt concentration in nearby non-isolated lakes, calculate the percentage of Lake Parsons which has evaporated since it became isolated.

Answer 1

68,2%

Step-by-step explanation:

Supposing the initial salt concentration of lake Parsons is the same of non-isolated lakes, 6,67L, and the change of salt concentration in isolated lake is just for water evaporation it is possible to write:

6,67gL⁻¹×X = 21gL⁻¹×Y

-Where X is the initial water and Y is the water that remains in the isolated lake-

Thus:

6,67X = 21Y

0,318 = Y/X

0,318 is the ratio of water that remains between total water. To obtain the ratio of evaporated water:

1-0,318 = 0,682

In percentage: 68,2%

I hope it helps!