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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.

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TheSandman1337
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 [tex] \frac{x*4.8}{z} = 55.82[/tex] . Solving for z/x we get: [tex] \frac{x}{z} = \frac{55.82}{4.8} [/tex] 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.
PBCHEM

Answer : 91.41%

Explanation :

As per geologist measurement, the given salt concentration of Lake Parsons (isolated one) : 55.82 g/L

salt concentration of other Lakes (non-isolated ones) : 4.8 g/L

Simply calculating by taking the ratios of the salts found in both the areas;

[tex]\frac{55.82 g/l}{4.8 g/l}[/tex] = 11.629

Which indicates that the salinity of Lake Parsons is 11.629 times higher. And the evaporation of the lake also increased with it.

To know the exact amount in percent taking the ratio with 100 and 11.629 we get;

∴ [tex]\frac{100}{11.629}[/tex] = 8.59 %

Also, to find the %lost we have to subtract this value from 100

100 - 8.59 = 91.41%.

∴ The total percentage of lake parson which has evaporated since it became isolated is 91.41%.