Assume an organic compound has a partition coefficient between water and ethyl acetate equal to 9.73. If there are initially 9.65 grams of the compound dissolved in 80.0 mL of water, how many grams will remain in the aqueous layer after extraction with two 10.0 mL portions of ethyl acetate?

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Answer:

[tex]\boxed{\text{1.96 g}}[/tex]

Explanation:

[tex]K = \dfrac{c_{\text{org}}}{c_{\text{aq}}} = 9.73[/tex]

1. First extraction

Let x = mass of compound extracted into ethyl acetate. Then

[tex]\begin{array}{rcl}9.73 & = & \dfrac{x/10.0}{(9.65 - x)/80.0}\\\\9.73\times (9.65 - x)/80.0  & = & x/10.0\\9.73\times (9.65 - x) & = & 8.00x\\93.89 - 9.73x & = & 8.00x\\17.73x & = & 93.89\\x & = & 5.30\\\end{array}[/tex]

So, 5.30 g are extracted into the ethyl acetate.

Mass remaining in water = (9.65 – 5.30) g = 4.35 g

2. Second extraction

[tex]\begin{array}{rcl}9.73 & = & \dfrac{x/10.0}{(4.35 - x)/80.0}\\\\9.73\times (4.35 - x)/80.0  & = & x/10.0\\9.73\times (4.35 - x) & = & 8.00x\\42.33 - 9.73x & = & 8.00x\\17.73x & = & 42.33\\x & = & 2.39\\\end{array}\\\text{So, 2.39 g are extracted into the ethyl acetate.}\\\text{ Mass remaining in water = (4.35 -2.39) g } = \boxed{\textbf{1.96 g}}[/tex]

The partition coefficient is the proportion of the concentration. The mass remaining in the water is 1.96 gm.

What is extraction and partition coefficient?

Given,

  • Partition coefficient = 9.73
  • Initial Mass of the compound = 9.65 gm
  • The volume of water = 80 mL

Calculate the first extraction:

Mass of compound extracted into ethyl acetate = x

Solving for x,

[tex]\begin{aligned}9.73 &= \dfrac{\dfrac{\rm x}{10}}{\dfrac{9.65 - \rm x}{80}}\\\\93.89 - 9.73 \rm \rm x &= 8.00 \rm x\\\\\rm x &= 5.30\end{aligned}[/tex]

Thus, 5.30 g is extracted and the mass remaining in the water is calculated as,

[tex](9.65 - 5.30) \rm g = 4.35 g[/tex]

Calculate the second extraction:

[tex]\begin{aligned}9.73 &= \dfrac{\dfrac{\rm x}{10}}{\dfrac{4.35-\rm x}{80}}\\\\42.33 - 9.73 \rm x &= 8.00 \rm x\\\\\rm x &= 2.39\end{aligned}[/tex]

Thus, 2.39 g is extracted and the mass remaining in the water is calculated as,

[tex](4.35 - 2.39) \rm g = 1.96 g[/tex]

Therefore, 1.96 gm is the mass remaining.

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