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1. Diclofenac is a non-steroidal anti-inflammatory drug. if the water discharge of your diclofenac manufacturing facility contains 5.0 g/l diclofenac and you wish to remove 99.0% of the drug from 100 l wastewater using n-octane, how many liquid-liquid extraction should be done if you will use 50 l for each extraction? (ko=25.0) a) only 1 b) at least 2 c) at least 3 d) at least 4
Accepted Answer
This question involves liquid-liquid extraction, a common technique in chemistry used to separate compounds based on their solubility in different solvents. Here's how to approach the problem:
1. Calculate the initial mass of diclofenac:
Initial concentration = 5.0 g/L
Volume = 100 L
Initial mass = 5.0 g/L
100 L = 500 g
2. Determine the desired final mass of diclofenac:
You want to remove 99% of the diclofenac.
Final mass = 1% of initial mass = 0.01
500 g = 5 g
3. Use the distribution coefficient (Kd) to calculate the amount extracted in each stage:
Kd = 25.0 = (concentration in n-octane) / (concentration in water)
Let 'x' be the mass of diclofenac extracted in each stage.
After each extraction, the mass remaining in water is (500-x) g.
Applying the Kd equation: 25.0 = (x / 50 L) / ((500-x) g / 100 L)
4. Solve for 'x' to find the mass extracted per stage:
Solving the equation gives you x ≈ 480.8 g extracted in each stage.
5. Calculate the number of extractions needed:
After the first extraction, you'll have approximately 500 g - 480.8 g = 19.2 g remaining.
Since you need to reach 5 g, you'll likely need at least two extractions.
Therefore, the correct answer is (B) at least 2.
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