Ageochemist measures the concentration of salt dissolved in lake parsons and finds a concentration of . the geochemist also measures the concentration of salt in several nearby non-isolated lakes, and finds an average concentration of . 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. round each of your answers to significant digits.

Question:

A geochemist measures the concentration of salt dissolved in Lake Parsons, an isolated salt lake. He finds a concentration of 74 gL−1. The geochemist also measures the concentration of salt in several nearby non-isolated lakes, and finds an average concentration of 6.5 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.

The percentage of Lake Parsons evaporated is 91 %

Explanation:

Let us say that Lake Parsons water content initially = X and  salt content = Y

Therefore,

Y = 6.5 X          

After Lake Parsons became isolated, its salt content remained unchanged   i.e. Y

However, its water content decreased due to evaporation. Suppose now its water content = Z

Therefore we can write

Substituting the Y value

\frac{6.5X}{Z} = 74

Therefore the Lake Parsons have now 8.78 % of the initial water.

Now the percentage of Lake Parsons evaporated

= (100 - 8.78)

= 91.22

= 91 % (rounding to 2 significant digits)

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