Question 11 a geochemist measures the concentration of salt dissolved in lake parsons, an isolated salt lake. he finds a concentration of 55.82·gl−1. the geochemist also measures the concentration of salt in several nearby non-isolated lakes, and finds an average concentration of 4.8·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. round each of your answers to 2 significant digits.

Suppose that Lake Parsons had initially x liters of water in it. These x liters of water were actually a solution that also contained salts, specifically y gr of salts in total. We are adviced to assume that initially the salt concentration was 4.8g/l, hence we have that y/x=4.8 g/l . During the evaporation of the lake, we have that only water evaporated; let us call the new quantity of water z. The quantity of salts in the lake remained y (salts do not evaporate). Similarly, we have that y/z=55.82 g/l. By our first equation, we have that y=4.8*x. Substituting, we get that . Solving for z/x we get: hence z/x= 0.086. Thus the final water that remains is 8.60% of the initial water. Hence, 100%-8.60%=91.40% of the lake's water has evaporated.

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