Question
A vessel contains 50 liters of a solution with 40% acid.
10 liters of this solution are removed and replaced with a solution containing 70% acid. The process is repeated once more. What is the final concentration of acid in the solution?Solution
Initial acid = 40% of 50 liters = 20 liters. After first replacement: Acid remaining = 20 - 4 = 16 liters. Acid added = 7 liters. Total acid = 16 + 7 = 23 liters. After second replacement: Acid remaining = 23 - 4.6 = 18.4 liters. Acid added = 7 liters. Total acid = 18.4 + 7 = 25.4 liters. Final concentration = 25.4/50 × 100 = 50.8%
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