Answer:
4.93g are extracted
Explanation:
Partition coefficient (P) is defined as the ratio of solute dissolved in the organic solvent and the solute dissolved in the aqueous phase.
That is:
P = 7.5 = Concentration in dichloromethane / Concentration in water.
Knowing this, in the first extraction with 25mL of dichloromethane you will extract:
7.5 = (X/25mL) / (5g - X) / 100mL
<em>Where X is the amount of compound A that is extracted.</em>
7.5 = 100X / (125 - 25X)
937.5 - 187.5X = 100X
937.5 = 287.5X
<em>3.26g of A are extracted in the first extraction</em>.
In water will remain 5g - 3.26g = 1.74g
In the second extraction you will extract:
7.5 = (X/25mL) / (1.74g - X) / 100mL
7.5 = 100X / (43.5 - 25X)
326.25 - 187.5X = 100X
326.25 = 287.5X
<em>1.13g are extracted in the second extraction.</em>
And remain: 1.74g - 1.13g = 0.61g
In the third extraction you will extract:
7.5 = (X/25mL) / (0.61g - X) / 100mL
7.5 = 100X / (15.25 - 25X)
114.375 - 187.5X = 100X
114.375 = 287.5X
<em>0.40g are extracted in the third extraction.</em>
And remain: 0.61g - 0.40g = 0.21g
In the second extraction you will extract:
7.5 = (X/25mL) / (0.21g - X) / 100mL
7.5 = 100X / (5.25 - 25X)
39.375 - 187.5X = 100X
39.375 = 287.5X
<em>0.14g are extracted in the fourth extraction.</em>
Thus, after the three extractions you will extract: 0.14g + 0.40g + 1.13g + 3.26g = <em>4.93g are extracted</em>