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Difficulty: EasyMixture and Concentration

A container holds 2020 liters of a solution that is 15%15\% acid by volume. If 55 liters of pure water are added to the solution, what is the percentage concentration of acid in the resulting mixture?

Answer: 12 %

Answer

The concentration of acid in the resulting mixture is 12%.
The correct concentration is found by taking the invariant amount of pure acid (33 liters) and dividing it by the total updated volume of the liquid (2525 liters), which yields 325=0.12\frac{3}{25} = 0.12, or 12%12\%.

Step-by-Step Solution

1
Determine the amount of solute (pure acid) in the original mixture.
Amount of acid = 0.15×20=30.15 \times 20 = 3 liters.
The solution initially consists of 15%15\% acid out of a total volume of 2020 liters.
2
Determine the total volume of the new solution after dilution.
New total volume = 20+5=2520 + 5 = 25 liters.
Adding 55 liters of pure water increases the total liquid volume without adding any additional acid.
3
Compute the new percentage concentration.
New concentration = 325×100%=12%\frac{3}{25} \times 100\% = 12\%.
The concentration is the ratio of pure solute to total solution volume expressed as a percentage.

Key Concept

Dilution of a mixture by adding pure solvent
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Topics

Mixture and Concentration

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