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A 900-gram salt-and-water solution contains 80 g of salt.
This mixture is left in the open air, and 100 g of water evaporates
from the solution. What is the percent concentration of salt in the remaining solution?
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| Water evaporates, the salt not. |
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After evaporation 100 g of water, the mass of the mixture is 900 - 100 = 800 grams.
Of this mass, 80 grams is salt: it remains with no change.
So, the mass concentration of the remaining mixture is
= = 0.1 grams of salt per gram of the resulting mixture. ANSWER
Solved.
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The major lesson to learn from my solution is THIS :
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Water evaporates, the salt not.
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